@smallbook
@c %**end of header
-@c ======================================================================
-@c This document has three levels of rendition: PUBLISH, DISTRIB or PROOF,
-@c as decided by @set symbols. The PUBLISH rendition does not show
-@c notes or marks asking for revision. Most users will prefer having more
-@c information, even if this information is not fully revised for adequacy,
-@c so DISTRIB is the default for tar distributions. The PROOF rendition
-@c show all marks to the point of ugliness, but is nevertheless useful to
-@c those working on the manual itself.
-@c ======================================================================
-
-@ifclear PUBLISH
-@ifclear DISTRIB
-@ifclear PROOF
-@set DISTRIB
-@end ifclear
-@end ifclear
-@end ifclear
-
-@ifset PUBLISH
-@set RENDITION The book, version
-@end ifset
-
-@ifset DISTRIB
-@set RENDITION FTP release, version
-@end ifset
-
-@ifset PROOF
-@set RENDITION Proof reading version
-@end ifset
-
-@c ---------------------------------------------------------------------
-@c The @FIXME's, @UNREVISED and @c comments are part Fran@,{c}ois's work
-@c plan. These annotations are somewhat precious to him; he asks that I
-@c do not alter them inconsiderately. Much work is needed for GNU tar
-@c internals (the sources, the programs themselves). Revising the
-@c adequacy of the manual while revising the sources, and cleaning them
-@c both at the same time, seems to him like a good way to proceed.
-@c ---------------------------------------------------------------------
-
-@c Output marks for nodes needing revision, but not in PUBLISH rendition.
-
-@macro UNREVISED
-@ifclear PUBLISH
-@quotation
-@emph{(This message will disappear, once this node revised.)}
-@end quotation
-@end ifclear
-@end macro
-
-@c Output various FIXME information only in PROOF rendition.
-
-@macro FIXME{string}
-@allow-recursion
-@quote-arg
-@ifset PROOF
-@strong{<FIXME>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-ref{string}
-@quote-arg
-@ifset PROOF
-@strong{<REF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-pxref{string}
-@quote-arg
-@ifset PROOF
-@strong{<PXREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@macro FIXME-xref{string}
-@quote-arg
-@ifset PROOF
-@strong{<XREF>} \string\ @strong{</>}
-@end ifset
-
-@end macro
-
-@c @macro option{entry}
-@c @quote-arg
-@c @opindex{--\entry\}
-@c @value{\entry\}
-@c @end macro
-
-@macro GNUTAR
-@acronym{GNU} @command{tar}
-@end macro
-
-@set op-absolute-names @kbd{--absolute-names} (@kbd{-P})
-@set ref-absolute-names @ref{absolute}
-@set xref-absolute-names @xref{absolute}
-@set pxref-absolute-names @pxref{absolute}
-
-@set op-after-date @kbd{--after-date=@var{date}} (@kbd{--newer=@var{date}}, @kbd{-N @var{date}})
-@set ref-after-date @ref{after}
-@set xref-after-date @xref{after}
-@set pxref-after-date @pxref{after}
-
-@set op-append @kbd{--append} (@kbd{-r})
-@set ref-append @ref{add}
-@set xref-append @xref{add}
-@set pxref-append @pxref{add}
-
-@set op-atime-preserve @kbd{--atime-preserve}
-@set ref-atime-preserve @ref{Attributes}
-@set xref-atime-preserve @xref{Attributes}
-@set pxref-atime-preserve @pxref{Attributes}
-
-@set op-backup @kbd{--backup}
-@set ref-backup @ref{Backup options}
-@set xref-backup @xref{Backup options}
-@set pxref-backup @pxref{Backup options}
-
-@set op-block-number @kbd{--block-number} (@kbd{-R})
-@set ref-block-number @ref{verbose}
-@set xref-block-number @xref{verbose}
-@set pxref-block-number @pxref{verbose}
-
-@set op-blocking-factor @kbd{--blocking-factor=@var{512-size}} (@kbd{-b @var{512-size}})
-@set ref-blocking-factor @ref{Blocking Factor}
-@set xref-blocking-factor @xref{Blocking Factor}
-@set pxref-blocking-factor @pxref{Blocking Factor}
-
-@set op-bzip2 @kbd{--bzip2} (@kbd{-j})
-@set ref-bzip2 @ref{gzip}
-@set xref-bzip2 @xref{gzip}
-@set pxref-bzip2 @pxref{gzip}
-
-@set op-check-links @kbd{--check-links} (@kbd{-l})
-@set ref-check-links @ref{--check-links}
-@set xref-check-links @xref{--check-links}
-@set pxref-check-links @pxref{--check-links}
-
-@set op-checkpoint @kbd{--checkpoint}
-@set ref-checkpoint @ref{verbose}
-@set xref-checkpoint @xref{verbose}
-@set pxref-checkpoint @pxref{verbose}
-
-@set op-check-links @kbd{--check-links}
-
-@set op-compare @kbd{--compare} (@kbd{--diff}, @kbd{-d})
-@set ref-compare @ref{compare}
-@set xref-compare @xref{compare}
-@set pxref-compare @pxref{compare}
-
-@set op-compress @kbd{--compress} (@kbd{--uncompress}, @kbd{-Z})
-@set ref-compress @ref{gzip}
-@set xref-compress @xref{gzip}
-@set pxref-compress @pxref{gzip}
-
-@set op-concatenate @kbd{--concatenate} (@kbd{--catenate}, @kbd{-A})
-@set ref-concatenate @ref{concatenate}
-@set xref-concatenate @xref{concatenate}
-@set pxref-concatenate @pxref{concatenate}
-
-@set op-create @kbd{--create} (@kbd{-c})
-@set ref-create @ref{create}
-@set xref-create @xref{create}
-@set pxref-create @pxref{create}
-
-@set op-delete @kbd{--delete}
-@set ref-delete @ref{delete}
-@set xref-delete @xref{delete}
-@set pxref-delete @pxref{delete}
-
-@set op-dereference @kbd{--dereference} (@kbd{-h})
-@set ref-dereference @ref{dereference}
-@set xref-dereference @xref{dereference}
-@set pxref-dereference @pxref{dereference}
-
-@set op-directory @kbd{--directory=@var{directory}} (@kbd{-C @var{directory}})
-@set ref-directory @ref{directory}
-@set xref-directory @xref{directory}
-@set pxref-directory @pxref{directory}
-
-@set op-exclude @kbd{--exclude=@var{pattern}}
-@set ref-exclude @ref{exclude}
-@set xref-exclude @xref{exclude}
-@set pxref-exclude @pxref{exclude}
-
-@set op-exclude-from @kbd{--exclude-from=@var{file-of-patterns}} (@kbd{-X @var{file-of-patterns}})
-@set ref-exclude-from @ref{exclude}
-@set xref-exclude-from @xref{exclude}
-@set pxref-exclude-from @pxref{exclude}
-
-@set op-extract @kbd{--extract} (@kbd{--get}, @kbd{-x})
-@set ref-extract @ref{extract}
-@set xref-extract @xref{extract}
-@set pxref-extract @pxref{extract}
-
-@set op-file @kbd{--file=@var{archive-name}} (@kbd{-f @var{archive-name}})
-@set ref-file @ref{file}
-@set xref-file @xref{file}
-@set pxref-file @pxref{file}
-
-@set op-files-from @kbd{--files-from=@var{file-of-names}} (@kbd{-T @var{file-of-names}})
-@set ref-files-from @ref{files}
-@set xref-files-from @xref{files}
-@set pxref-files-from @pxref{files}
-
-@set op-force-local @kbd{--force-local}
-@set ref-force-local @ref{file}
-@set xref-force-local @xref{file}
-@set pxref-force-local @pxref{file}
-
-@set op-group @kbd{--group=@var{group}}
-@set ref-group @ref{Option Summary}
-@set xref-group @xref{Option Summary}
-@set pxref-group @pxref{Option Summary}
-
-@set op-gzip @kbd{--gzip} (@kbd{--gunzip}, @kbd{--ungzip}, @kbd{-z})
-@set ref-gzip @ref{gzip}
-@set xref-gzip @xref{gzip}
-@set pxref-gzip @pxref{gzip}
-
-@set op-help @kbd{--help}
-@set ref-help @ref{help}
-@set xref-help @xref{help}
-@set pxref-help @pxref{help}
-
-@set op-ignore-failed-read @kbd{--ignore-failed-read}
-@set ref-ignore-failed-read @ref{create options}
-@set xref-ignore-failed-read @xref{create options}
-@set pxref-ignore-failed-read @pxref{create options}
-
-@set op-ignore-zeros @kbd{--ignore-zeros} (@kbd{-i})
-@set ref-ignore-zeros @ref{Reading}
-@set xref-ignore-zeros @xref{Reading}
-@set pxref-ignore-zeros @pxref{Reading}
-
-@set op-incremental @kbd{--incremental} (@kbd{-G})
-@set ref-incremental @ref{Inc Dumps}
-@set xref-incremental @xref{Inc Dumps}
-@set pxref-incremental @pxref{Inc Dumps}
-
-@set op-info-script @kbd{--info-script=@var{script-name}} (@kbd{--new-volume-script=@var{script-name}}, @kbd{-F @var{script-name}})
-@set ref-info-script @ref{Multi-Volume Archives}
-@set xref-info-script @xref{Multi-Volume Archives}
-@set pxref-info-script @pxref{Multi-Volume Archives}
-
-@set op-interactive @kbd{--interactive} (@kbd{-w})
-@set ref-interactive @ref{interactive}
-@set xref-interactive @xref{interactive}
-@set pxref-interactive @pxref{interactive}
-
-@set op-keep-old-files @kbd{--keep-old-files} (@kbd{-k})
-@set ref-keep-old-files @ref{Writing}
-@set xref-keep-old-files @xref{Writing}
-@set pxref-keep-old-files @pxref{Writing}
-
-@set op-label @kbd{--label=@var{archive-label}} (@kbd{-V @var{archive-label}})
-@set ref-label @ref{label}
-@set xref-label @xref{label}
-@set pxref-label @pxref{label}
-
-@set op-list @kbd{--list} (@kbd{-t})
-@set ref-list @ref{list}
-@set xref-list @xref{list}
-@set pxref-list @pxref{list}
-
-@set op-listed-incremental @kbd{--listed-incremental=@var{snapshot-file}} (@kbd{-g @var{snapshot-file}})
-@set ref-listed-incremental @ref{Inc Dumps}
-@set xref-listed-incremental @xref{Inc Dumps}
-@set pxref-listed-incremental @pxref{Inc Dumps}
-
-@set op-mode @kbd{--mode=@var{permissions}}
-@set ref-mode @ref{Option Summary}
-@set xref-mode @xref{Option Summary}
-@set pxref-mode @pxref{Option Summary}
-
-@set op-multi-volume @kbd{--multi-volume} (@kbd{-M})
-@set ref-multi-volume @ref{Multi-Volume Archives}
-@set xref-multi-volume @xref{Multi-Volume Archives}
-@set pxref-multi-volume @pxref{Multi-Volume Archives}
-
-@set op-newer-mtime @kbd{--newer-mtime=@var{date}}
-@set ref-newer-mtime @ref{after}
-@set xref-newer-mtime @xref{after}
-@set pxref-newer-mtime @pxref{after}
-
-@set op-no-recursion @kbd{--no-recursion}
-@set ref-no-recursion @ref{recurse}
-@set xref-no-recursion @xref{recurse}
-@set pxref-no-recursion @pxref{recurse}
-
-@set op-no-same-owner @kbd{--no-same-owner} (@kbd{-o})
-@set ref-no-same-owner @ref{Attributes}
-@set xref-no-same-owner @xref{Attributes}
-@set pxref-no-same-owner @pxref{Attributes}
-
-@set op-no-same-permissions @kbd{--no-same-permissions}
-@set ref-no-same-permissions @ref{Attributes}
-@set xref-no-same-permissions @xref{Attributes}
-@set pxref-no-same-permissions @pxref{Attributes}
-
-@set op-null @kbd{--null}
-@set ref-null @ref{files}
-@set xref-null @xref{files}
-@set pxref-null @pxref{files}
-
-@set op-numeric-owner @kbd{--numeric-owner}
-@set ref-numeric-owner @ref{Attributes}
-@set xref-numeric-owner @xref{Attributes}
-@set pxref-numeric-owner @pxref{Attributes}
-
-@set op-occurrence @kbd{--occurrence}
-@set ref-occurrence @ref{--occurrence}
-@set xref-occurrence @xref{--occurrence}
-@set pxref-occurrence @pxref{--occurrence}
-
-@set op-old-archive @kbd{--old-archive} (@kbd{-o})
-@set ref-old-archive @ref{old}
-@set xref-old-archive @xref{old}
-@set pxref-old-archive @pxref{old}
-
-@set op-one-file-system @kbd{--one-file-system} (@kbd{-l})
-@set ref-one-file-system @ref{one}
-@set xref-one-file-system @xref{one}
-@set pxref-one-file-system @pxref{one}
-
-@set op-overwrite @kbd{--overwrite}
-@set ref-overwrite @ref{Overwrite Old Files}
-@set xref-overwrite @xref{Overwrite Old Files}
-@set pxref-overwrite @pxref{Overwrite Old Files}
-
-@set op-owner @kbd{--owner=@var{user}}
-@set ref-owner @ref{Option Summary}
-@set xref-owner @xref{Option Summary}
-@set pxref-owner @pxref{Option Summary}
-
-@set op-format @kbd{--format}
-@set ref-format @ref{format}
-@set xref-format @xref{format}
-@set pxref-format @pxref{format}
-
-@set op-format-v7 @kbd{--format=v7}
-@set op-format-gnu @kbd{--format=gnu}
-@set op-format-oldgnu @kbd{--format=oldgnu}
-@set op-format-posix @kbd{--format=posix}
-
-@set op-posix @kbd{--posix}
-@set ref-posix @ref{posix}
-@set xref-posix @xref{posix}
-@set pxref-posix @pxref{posix}
-
-@set op-preserve @kbd{--preserve}
-@set ref-preserve @ref{Attributes}
-@set xref-preserve @xref{Attributes}
-@set pxref-preserve @pxref{Attributes}
-
-@set op-record-size @kbd{--record-size=@var{size}}
-@set ref-record-size @ref{Blocking}
-@set xref-record-size @xref{Blocking}
-@set pxref-record-size @pxref{Blocking}
-
-@set op-recursive-unlink @kbd{--recursive-unlink}
-@set ref-recursive-unlink @ref{Writing}
-@set xref-recursive-unlink @xref{Writing}
-@set pxref-recursive-unlink @pxref{Writing}
-
-@set op-read-full-records @kbd{--read-full-records} (@kbd{-B})
-@set ref-read-full-records @ref{Blocking}
-@set xref-read-full-records @xref{Blocking}
-@set pxref-read-full-records @pxref{Blocking}
-@c FIXME: or should it be Reading, or Blocking Factor
-
-@set op-remove-files @kbd{--remove-files}
-@set ref-remove-files @ref{Writing}
-@set xref-remove-files @xref{Writing}
-@set pxref-remove-files @pxref{Writing}
-
-@set op-rsh-command @kbd{rsh-command=@var{command}}
-
-@set op-same-order @kbd{--same-order} (@kbd{--preserve-order}, @kbd{-s})
-@set ref-same-order @ref{Scarce}
-@set xref-same-order @xref{Scarce}
-@set pxref-same-order @pxref{Scarce}
-@c FIXME: or should it be Reading, or Attributes?
-
-@set op-same-owner @kbd{--same-owner}
-@set ref-same-owner @ref{Attributes}
-@set xref-same-owner @xref{Attributes}
-@set pxref-same-owner @pxref{Attributes}
-
-@set op-same-permissions @kbd{--same-permissions} (@kbd{--preserve-permissions}, @kbd{-p})
-@set ref-same-permissions @ref{Attributes}
-@set xref-same-permissions @xref{Attributes}
-@set pxref-same-permissions @pxref{Attributes}
-@c FIXME: or should it be Writing?
-
-@set op-show-omitted-dirs @kbd{--show-omitted-dirs}
-@set ref-show-omitted-dirs @ref{verbose}
-@set xref-show-omitted-dirs @xref{verbose}
-@set pxref-show-omitted-dirs @pxref{verbose}
-
-@set op-sparse @kbd{--sparse} (@kbd{-S})
-@set ref-sparse @ref{sparse}
-@set xref-sparse @xref{sparse}
-@set pxref-sparse @pxref{sparse}
-
-@set op-starting-file @kbd{--starting-file=@var{name}} (@kbd{-K @var{name}})
-@set ref-starting-file @ref{Scarce}
-@set xref-starting-file @xref{Scarce}
-@set pxref-starting-file @pxref{Scarce}
-
-@set op-strip-path @kbd{--strip-path}
-@set ref-strip-path @ref{--strip-path}
-@set xref-strip-path @xref{--strip-path}
-@set pxref-strip-path @pxref{--strip-path}
-
-@set op-suffix @kbd{--suffix=@var{suffix}}
-@set ref-suffix @ref{Backup options}
-@set xref-suffix @xref{Backup options}
-@set pxref-suffix @pxref{Backup options}
-
-@set op-tape-length @kbd{--tape-length=@var{1024-size}} (@kbd{-L @var{1024-size}})
-@set ref-tape-length @ref{Using Multiple Tapes}
-@set xref-tape-length @xref{Using Multiple Tapes}
-@set pxref-tape-length @pxref{Using Multiple Tapes}
-
-@set op-to-stdout @kbd{--to-stdout} (@kbd{-O})
-@set ref-to-stdout @ref{Writing}
-@set xref-to-stdout @xref{Writing}
-@set pxref-to-stdout @pxref{Writing}
-
-@set op-totals @kbd{--totals}
-@set ref-totals @ref{verbose}
-@set xref-totals @xref{verbose}
-@set pxref-totals @pxref{verbose}
-
-@set op-touch @kbd{--touch} (@kbd{-m})
-@set ref-touch @ref{Writing}
-@set xref-touch @xref{Writing}
-@set pxref-touch @pxref{Writing}
-
-@set op-unlink-first @kbd{--unlink-first} (@kbd{-U})
-@set ref-unlink-first @ref{Writing}
-@set xref-unlink-first @xref{Writing}
-@set pxref-unlink-first @pxref{Writing}
-
-@set op-update @kbd{--update} (@kbd{-u})
-@set ref-update @ref{update}
-@set xref-update @xref{update}
-@set pxref-update @pxref{update}
-
-@set op-use-compress-prog @kbd{--use-compress-prog=@var{program}}
-@set ref-use-compress-prog @ref{gzip}
-@set xref-use-compress-prog @xref{gzip}
-@set pxref-use-compress-prog @pxref{gzip}
-
-@set op-verbose @kbd{--verbose} (@kbd{-v})
-@set ref-verbose @ref{verbose}
-@set xref-verbose @xref{verbose}
-@set pxref-verbose @pxref{verbose}
-
-@set op-verify @kbd{--verify} (@kbd{-W})
-@set ref-verify @ref{verify}
-@set xref-verify @xref{verify}
-@set pxref-verify @pxref{verify}
-
-@set op-version @kbd{--version}
-@set ref-version @ref{help}
-@set xref-version @xref{help}
-@set pxref-version @pxref{help}
-
-@set op-volno-file @kbd{--volno-file=@var{file-of-number}}
-@set ref-volno-file @ref{Using Multiple Tapes}
-@set xref-volno-file @xref{Using Multiple Tapes}
-@set pxref-volno-file @pxref{Using Multiple Tapes}
+@include rendition.texi
+@include value.texi
@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
from archives.
Copyright @copyright{} 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
-2003 Free Software Foundation, Inc.
+2003, 2004 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
@dircategory Individual utilities
@direntry
-* tar: (tar)tar invocation. Invoking @GNUTAR{}
+* tar: (tar)tar invocation. Invoking @GNUTAR{}.
@end direntry
@shorttitlepage @acronym{GNU} @command{tar}
@titlepage
@title @acronym{GNU} tar: an archiver tool
@subtitle @value{RENDITION} @value{VERSION}, @value{UPDATED}
-@author Melissa Weisshaus, Jay Fenlason,
-@author Thomas Bushnell, n/BSG, Amy Gorin
-@c he said to remove it: Fran@,{c}ois Pinard
-@c i'm thinking about how the author page *should* look. -mew 2may96
+@author John Gilmore, Jay Fenlason et al.
@page
@vskip 0pt plus 1filll
* Date input formats::
* Formats::
* Media::
+
+Appendices
+
+* Genfile::
+* Snapshot Files::
* Free Software Needs Free Documentation::
* Copying This Manual::
* Index::
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
* delete::
* compare::
-How to Add Files to Existing Archives: @code{--append}
+How to Add Files to Existing Archives: @option{--append}
* appending files:: Appending Files to an Archive
* multiple::
* how to update::
-Options Used by @code{--create}
+Options Used by @option{--create}
* Ignore Failed Read::
-Options Used by @code{--extract}
+Options Used by @option{--extract}
* Reading:: Options to Help Read Archives
* Writing:: Changing How @command{tar} Writes Files
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
Performing Backups and Restoring Files
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
Setting Parameters for Backups and Restoration
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
Choosing Files and Names for @command{tar}
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
Reading Names from a File
* controlling pattern-patching with exclude::
* problems with exclude::
-Crossing Filesystem Boundaries
+Crossing File System Boundaries
* directory:: Changing Directory
* absolute:: Absolute File Names
* Day of week items:: Monday and others.
* Relative items in date strings:: next tuesday, 2 years ago.
* Pure numbers in date strings:: 19931219, 1440.
-* Authors of getdate:: Bellovin, Eggert, Salz, Berets, et al.
+* Seconds since the Epoch:: @@1078100502.
+* Authors of get_date:: Bellovin, Eggert, Salz, Berets, et al.
Controlling the Archive Format
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
-* posix:: @sc{posix} archives
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
* Large or Negative Values:: Large files, negative time stamps, etc.
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
+GNU tar internals and development
+
+* Genfile::
+* Snapshot Files::
Copying This Manual
@chapter Introduction
@GNUTAR{} creates
-and manipulates (@dfn{archives}) which are actually collections of
+and manipulates @dfn{archives} which are actually collections of
many other files; the program provides users with an organized and
systematic method for controlling a large amount of data.
The name ``tar'' originally came from the phrase ``Tape ARchive'', but
* Definitions:: Some Definitions
* What tar Does:: What @command{tar} Does
* Naming tar Archives:: How @command{tar} Archives are Named
-* posix compliance::
* Current status:: Current development status of @GNUTAR{}
* Authors:: @GNUTAR{} Authors
* Reports:: Reporting bugs or suggestions
In addition, one section of this manual (@pxref{Standard}) contains a
big quote which is taken directly from @command{tar} sources.
-In general, we give both the long and short (abbreviated) option names
+In general, we give both long and short (abbreviated) option names
at least once in each section where the relevant option is covered, so
that novice readers will become familiar with both styles. (A few
options have no short versions, and the relevant sections will
archives. An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth. (In addition, archives record access
-permissions, user and group, size in bytes, and last modification time.
+permissions, user and group, size in bytes, and data modification time.
Some archives also record the file names in each archived directory, as
well as other file and directory information.) You can use @command{tar}
to @dfn{create} a new archive in a specified directory.
manual, we use the term @dfn{file} to refer only to files accessible in
the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive. Similarly, a
-@dfn{file name} is the name of a file, as it resides in the filesystem,
+@dfn{file name} is the name of a file, as it resides in the file system,
and a @dfn{member name} is the name of an archive member within the
archive.
@cindex extraction
@cindex unpacking
The term @dfn{extraction} refers to the process of copying an archive
-member (or multiple members) into a file in the filesystem. Extracting
+member (or multiple members) into a file in the file system. Extracting
all the members of an archive is often called @dfn{extracting the
archive}. The term @dfn{unpack} can also be used to refer to the
extraction of many or all the members of an archive. Extracting an
accidental destruction of the information in those files.
@GNUTAR{} has special features that allow it to be
used to make incremental and full dumps of all the files in a
-filesystem.
+file system.
@item Transportation
You can create an archive on one system, transfer it to another system,
this manual, we consistently refer to ``archives'' and ``archive
members'' to make learning to use @command{tar} easier for novice users.
-@node posix compliance
-@section @sc{posix} Compliance
-
-@noindent
-@FIXME{must ask franc,ois about this. dan hagerty thinks this might
-be an issue, but we're not really sure at this time. dan just tried a
-test case of mixing up options' orders while the variable was set, and
-there was no problem...}
-@FIXME{I did not notice any problems either. Besides, the only piece
-of code that really uses POSIXLY_CORRECT is the one that forces
-creation of POSIX archives. I guess this paragraph should be removed.
-
---gray}
-
-
-We make some of our recommendations throughout this book for one
-reason in addition to what we think of as ``good sense''. The main
-additional reason for a recommendation is to be compliant with the
-@sc{posix} standards. If you set the shell environment variable
-@env{POSIXLY_CORRECT}, @GNUTAR{} will force you to
-adhere to these standards. Therefore, if this variable is set and you
-violate one of the @sc{posix} standards in the way you phrase a
-command, for example, @GNUTAR{} will not allow the
-command and will signal an error message. You would then have to
-reorder the options or rephrase the command to comply with the
-@sc{posix} standards.
-
-Notice also, that if this environment variable is set, @GNUTAR{}
-will create @acronym{POSIX} archives. Currently this means that
-no @acronym{GNU} extensions will be allowed (@pxref{posix}).
-
@node Current status
@section Current development status of @GNUTAR{}
@item Improve compatibility between @GNUTAR{} and other @command{tar}
implementations.
@item Switch to using @acronym{POSIX} archives.
-@item Revise sparse file handling.
-@item Revise multiple volume processing.
+@item Revise sparse file handling and multiple volume processing.
+@item Merge with the @acronym{GNU} @code{paxutils} project.
@end itemize
-The following issues need mentioning:
+Some of these aims are already attained, while others are still
+being worked upon. From the point of view of an end user, the
+following issues need special mentioning:
@table @asis
@item Use of short option @option{-o}.
+
Earlier versions of @GNUTAR{} understood @option{-o} command line
-option as a synonim for @option{--old-archive}.
+option as a synonym for @option{--old-archive}.
@GNUTAR{} starting from version 1.13.90 understands this option as
-a synonim for @option{--no-same-owner}. This is compatible with
+a synonym for @option{--no-same-owner}. This is compatible with
UNIX98 @command{tar} implementations.
However, to facilitate transition, @option{-o} option retains its
old semantics when it is used with one of archive-creation commands.
Users are encouraged to use @value{op-format-oldgnu} instead.
+It is especially important, since versions of @acronym{GNU} Automake
+up to and including 1.8.4 invoke tar with this option to produce
+distribution tarballs. @xref{Formats,v7}, for the detailed discussion
+of this issue and its implications.
+
Future versions of @GNUTAR{} will understand @option{-o} only as a
-synonim for @option{--no-same-owner}.
+synonym for @option{--no-same-owner}.
@item Use of short option @option{-l}
+
Earlier versions of @GNUTAR{} understood @option{-l} option as a
-synonim for @samp{--one-file-system}. Such usage is deprecated.
-For compatiblity with other implementations future versions of
-@GNUTAR{} will understand this option as a synonim for
+synonym for @option{--one-file-system}. Such usage is deprecated.
+For compatibility with other implementations future versions of
+@GNUTAR{} will understand this option as a synonym for
@option{--check-links}.
@item Use of options @option{--portability} and @option{--old-archive}
-These options are deprecated. Please use @option{--format=v7} instead.
+
+These options are deprecated. Please use @option{--format=v7} instead.
@item Use of option @option{--posix}
-This option is deprecated. Please use @option{--format=posix} instead.
+
+This option is deprecated. Please use @option{--format=posix} instead.
@end table
@node Authors
@GNUTAR{} was originally written by John Gilmore,
and modified by many people. The @acronym{GNU} enhancements were
written by Jay Fenlason, then Joy Kendall, and the whole package has
-been further maintained by Thomas Bushnell, n/BSG, and finally
-Fran@,{c}ois Pinard, with the help of numerous and kind users.
+been further maintained by Thomas Bushnell, n/BSG, Fran@,{c}ois
+Pinard, Paul Eggert, and finally Sergey Poznyakoff with the help of
+numerous and kind users.
We wish to stress that @command{tar} is a collective work, and owes much to
all those people who reported problems, offered solutions and other
For version 1.12, Daniel Hagerty contributed a great deal of technical
consulting. In particular, he is the primary author of @ref{Backups}.
-In July, 2003 @GNUTAR{} was put on CVS at @url{savannah.gnu.org}, and
-an active development and maintainance work has started
-again. Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
+In July, 2003 @GNUTAR{} was put on CVS at savannah.gnu.org
+(see @url{http://savannah.gnu.org/projects/tar}), and
+active development and maintenance work has started
+again. Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
Poznyakoff and Jeff Bailey.
Support for @acronym{POSIX} archives was added by Sergey Poznyakoff.
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.
+When reporting a bug, please be sure to include as much detail as
+possible, in order to reproduce it. @FIXME{Be more specific, I'd
+like to make this node as detailed as 'Bug reporting' node in Emacs
+manual}.
+
@node Tutorial
@chapter Tutorial Introduction to @command{tar}
This chapter guides you through some basic examples of three @command{tar}
-operations: @samp{--create}, @samp{--list}, and @samp{--extract}. If
+operations: @option{--create}, @option{--list}, and @option{--extract}. If
you already know how to use some other version of @command{tar}, then you
may not need to read this chapter. This chapter omits most complicated
details about how @command{tar} works.
use some basic utilities. For example, you should know how to create,
list, copy, rename, edit, and delete files and directories; how to
change between directories; and how to figure out where you are in the
-filesystem. You should have some basic understanding of directory
+file system. You should have some basic understanding of directory
structure and how files are named according to which directory they are
in. You should understand concepts such as standard output and standard
input, what various definitions of the term ``argument'' mean, and the
precedes lines you should type; to make this more clear, those lines are
shown in @kbd{this font}, as opposed to lines which represent the
computer's response; those lines are shown in @code{this font}, or
-sometimes @samp{like this}. When we have lines which are too long to be
-displayed in any other way, we will show them like this:
+sometimes @samp{like this}.
-@smallexample
-This is an example of a line which would otherwise not fit in this space.
-@end smallexample
-
-@FIXME{how often do we use smallexample?}
+@c When we have lines which are too long to be
+@c displayed in any other way, we will show them like this:
@node basic tar options
@section Basic @command{tar} Operations and Options
exist in @GNUTAR{} for compatibility with Unix
@command{tar}. We present a full discussion of this way of writing
options and operations appears in @ref{Old Options}, and we discuss
-the other two styles of writing options in @ref{Mnemonic Options} and
+the other two styles of writing options in @ref{Mnemonic Options}, and
@ref{Short Options}.)
In the examples and in the text of this tutorial, we usually use the
this chapter will cover how to use these operations in detail. We will
present the rest of the operations in the next chapter.
-@table @kbd
+@table @option
@item --create
@itemx -c
Create a new @command{tar} archive.
To understand how to run @command{tar} in the three operating modes listed
previously, you also need to understand how to use two of the options to
-@command{tar}: @samp{--file} (which takes an archive file as an argument)
-and @samp{--verbose}. (You are usually not @emph{required} to specify
+@command{tar}: @option{--file} (which takes an archive file as an argument)
+and @option{--verbose}. (You are usually not @emph{required} to specify
either of these options when you run @command{tar}, but they can be very
useful in making things more clear and helping you avoid errors.)
@end menu
@node file tutorial
-@unnumberedsubsec The @samp{--file} Option
+@unnumberedsubsec The @option{--file} Option
-@table @kbd
+@table @option
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Specify the name of an archive file.
@ref{file}.
@node verbose tutorial
-@unnumberedsubsec The @samp{--verbose} Option
+@unnumberedsubsec The @option{--verbose} Option
-@table @kbd
+@table @option
@item --verbose
@itemx -v
Show the files being worked on as @command{tar} is running.
@value{op-verbose} shows details about the results of running
@command{tar}. This can be especially useful when the results might not be
obvious. For example, if you want to see the progress of @command{tar} as
-it writes files into the archive, you can use the @samp{--verbose}
+it writes files into the archive, you can use the @option{--verbose}
option. In the beginning, you may find it useful to use
-@samp{--verbose} at all times; when you are more accustomed to
+@option{--verbose} at all times; when you are more accustomed to
@command{tar}, you will likely want to use it at certain times but not at
-others. We will use @samp{--verbose} at times to help make something
+others. We will use @option{--verbose} at times to help make something
clear, and we will give many examples both using and not using
-@samp{--verbose} to show the differences.
+@option{--verbose} to show the differences.
-Sometimes, a single instance of @samp{--verbose} on the command line
+Sometimes, a single instance of @option{--verbose} on the command line
will show a full, @samp{ls} style listing of an archive or files,
-@c FIXME: Describe the exact output format, e.g., how hard links are displayed.
-giving sizes, owners, and similar information. Other times,
-@samp{--verbose} will only show files or members that the particular
+giving sizes, owners, and similar information. @FIXME{Describe the
+exact output format, e.g., how hard links are displayed.}
+Other times, @option{--verbose} will only show files or members that the particular
operation is operating on at the time. In the latter case, you can
-use @samp{--verbose} twice in a command to get a listing such as that
+use @option{--verbose} twice in a command to get a listing such as that
in the former case. For example, instead of saying
@smallexample
@noindent
Note that you must double the hyphens properly each time.
-Later in the tutorial, we will give examples using @w{@samp{--verbose
+Later in the tutorial, we will give examples using @w{@option{--verbose
--verbose}}.
@node help tutorial
-@unnumberedsubsec Getting Help: Using the @code{--help} Option
+@unnumberedsubsec Getting Help: Using the @option{--help} Option
-@table @kbd
+@table @option
@item --help
-The @samp{--help} option to @command{tar} prints out a very brief list of
+The @option{--help} option to @command{tar} prints out a very brief list of
all operations and option available for the current version of
@command{tar} available on your system.
@end table
One of the basic operations of @command{tar} is @value{op-create}, which
you use to create a @command{tar} archive. We will explain
-@samp{--create} first because, in order to learn about the other
+@option{--create} first because, in order to learn about the other
operations, you will find it useful to have an archive available to
practice on.
@file{blues}, @file{folk}, and @file{jazz}. The archive is called
@file{collection.tar}.
-This section will proceed slowly, detailing how to use @samp{--create}
+This section will proceed slowly, detailing how to use @option{--create}
in @code{verbose} mode, and showing examples using both short and long
forms. In the rest of the tutorial, and in the examples in the next
chapter, we will proceed at a slightly quicker pace. This section
@command{tar}, to avoid errors).
Note that the part of the command which says,
-@w{@kbd{--file=collection.tar}} is considered to be @emph{one} argument.
+@w{@option{--file=collection.tar}} is considered to be @emph{one} argument.
If you substituted any other string of characters for
@kbd{collection.tar}, then that string would become the name of the
archive file you create.
into the habit of typing options in the order that makes inherent sense.
@xref{short create}, for more information on this.
-In this example, you type the command as shown above: @samp{--create}
+In this example, you type the command as shown above: @option{--create}
is the operation which creates the new archive
-(@file{collection.tar}), and @samp{--file} is the option which lets
+(@file{collection.tar}), and @option{--file} is the option which lets
you give it the name you chose. The files, @file{blues}, @file{folk},
and @file{jazz}, are now members of the archive, @file{collection.tar}
-(they are @dfn{file name arguments} to the @samp{--create} operation).
+(they are @dfn{file name arguments} to the @option{--create} operation).
@FIXME{xref here to the discussion of file name args?}Now that they are
in the archive, they are called @emph{archive members}, not files.
-@FIXME{xref to definitions?}
+(@pxref{Definitions,members}).
When you create an archive, you @emph{must} specify which files you
want placed in the archive. If you do not specify any archive
members, @GNUTAR{} will complain.
-If you now list the contents of the working directory (@kbd{ls}), you will
+If you now list the contents of the working directory (@command{ls}), you will
find the archive file listed as well as the files you saw previously:
@smallexample
Use @value{op-append} instead. @xref{append}.
@node create verbose
-@subsection Running @samp{--create} with @samp{--verbose}
+@subsection Running @option{--create} with @option{--verbose}
If you include the @value{op-verbose} option on the command line,
@command{tar} will list the files it is acting on as it is working. In
@end smallexample
This example is just like the example we showed which did not use
-@samp{--verbose}, except that @command{tar} generated the remaining lines
+@option{--verbose}, except that @command{tar} generated the remaining lines
@iftex
(note the different font styles).
@end iftex
@noindent
In this case, @command{tar} will make an archive file called @file{v},
containing the files @file{blues}, @file{folk}, and @file{jazz}, because
-the @samp{v} is the closest ``file name'' to the @samp{-f} option, and
+the @samp{v} is the closest ``file name'' to the @option{-f} option, and
is thus taken to be the chosen archive file name. @command{tar} will try
to add a file called @file{collection.tar} to the @file{v} archive file;
if the file @file{collection.tar} did not already exist, @command{tar} will
report an error indicating that this file does not exist. If the file
@file{collection.tar} does already exist (e.g., from a previous command
you may have run), then @command{tar} will add this file to the archive.
-Because the @samp{-v} option did not get registered, @command{tar} will not
+Because the @option{-v} option did not get registered, @command{tar} will not
run under @samp{verbose} mode, and will not report its progress.
The end result is that you may be quite confused about what happened,
@noindent
It would be very easy to put the wrong string of characters
-immediately following the @samp{-f}, but doing that could sacrifice
+immediately following the @option{-f}, but doing that could sacrifice
valuable data.
For this reason, we recommend that you pay very careful attention to
does what, and therefore where different names have to be placed.
(Placing options in an unusual order can also cause @command{tar} to
report an error if you have set the shell environment variable
-@env{POSIXLY_CORRECT}; @pxref{posix compliance} for more information
-on this.)
+@env{POSIXLY_CORRECT}.)
@node create dir
@subsection Archiving Directories
@noindent
This will put you into the directory which contains @file{practice},
-i.e. your home directory. Once in the superior directory, you can
+i.e., your home directory. Once in the superior directory, you can
specify the subdirectory, @file{practice}, as a file name argument. To
store @file{practice} in the new archive file @file{music.tar}, type:
Be sure to use a @value{op-file} option just as with @value{op-create}
to specify the name of the archive.
-If you use the @value{op-verbose} option with @samp{--list}, then
+If you use the @value{op-verbose} option with @option{--list}, then
@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
-rw-rw-rw- myself user 62 1990-05-23 10:55 folk
@end smallexample
-@cindex File name arguments, using @code{--list} with
-@cindex @code{--list} with file name arguments
+@cindex listing member and file names
+@anchor{listing member and file names}
+It is important to notice that the output of @kbd{tar --list
+--verbose} does not necessarily match that produced by @kbd{tar
+--create --verbose} while creating the archive. It is because
+@GNUTAR{}, unless told explicitly not to do so, removes some directory
+prefixes from file names before storing them in the archive
+(@xref{absolute}, for more information). In other
+words, in verbose mode @GNUTAR{} shows @dfn{file names} when creating
+an archive and @dfn{member names} when listing it. Consider this
+example:
+
+@smallexample
+@group
+$ @kbd{tar cfv archive /etc/mail}
+tar: Removing leading `/' from member names
+/etc/mail/
+/etc/mail/sendmail.cf
+/etc/mail/aliases
+$ @kbd{tar tf archive}
+etc/mail/
+etc/mail/sendmail.cf
+etc/mail/aliases
+@end group
+@end smallexample
+
+@cindex @option{--show-stored-names} described
+ This default behavior can sometimes be inconvenient. You can force
+@GNUTAR{} show member names when creating archive by supplying
+@option{--show-stored-names} option.
+
+@table @option
+@item --show-stored-names
+Print member (not @emph{file}) names when creating the archive.
+@end table
+
+@cindex File name arguments, using @option{--list} with
+@cindex @option{--list} with file name arguments
You can specify one or more individual member names as arguments when
using @samp{list}. In this case, @command{tar} will only list the
names of members you identify. For example, @w{@kbd{tar --list
with @file{folk}, because @file{folk} is in the archive file
@file{collection.tar}. If you are not sure of the exact file name, try
listing all the files in the archive and searching for the one you
-expect to find; remember that if you use @samp{--list} with no file
+expect to find; remember that if you use @option{--list} with no file
names as arguments, @command{tar} will print the names of all the members
stored in the specified archive.
@node list dir
@unnumberedsubsec Listing the Contents of a Stored Directory
-@UNREVISED
-
-@FIXME{i changed the order of these nodes around and haven't had a
-chance to play around with this node's example, yet. i have to play
-with it and see what it actually does for my own satisfaction, even if
-what it says *is* correct..}
To get information about the contents of an archived directory,
use the directory name as a file name argument in conjunction with
Extracting an archive does not modify the archive in any way; you can
extract it multiple times if you want or need to.
-Using @samp{--extract}, you can extract an entire archive, or specific
+Using @option{--extract}, you can extract an entire archive, or specific
files. The files can be directories containing other files, or not. As
with @value{op-create} and @value{op-list}, you may use the short or the
long form of the operation without affecting the performance.
one of the files you had placed in the archive @file{collection.tar}
earlier (say, @file{blues}), you can extract it from the archive without
changing the archive's structure. It will be identical to the original
-file @file{blues} that you deleted. @FIXME{check this; will the times,
-permissions, owner, etc be the same, also?}
+file @file{blues} that you deleted. @FIXME{At the time of this
+writing, atime and ctime are not restored. Since this is a tutorial
+for a beginning user, it should hardly be mentioned here. Maybe in
+a footnote? --gray}.
First, make sure you are in the @file{practice} directory, and list the
files in the directory. Now, delete the file, @samp{blues}, and list
@noindent
If you list the files in the directory again, you will see that the file
-@file{blues} has been restored, with its original permissions, creation
+@file{blues} has been restored, with its original permissions, data modification
times, and owner.@FIXME{This is only accidentally true, but not in
general. In most cases, one has to be root for restoring the owner, and
use a special option for restoring permissions. Here, it just happens
(@pxref{list}).
You can extract a file to standard output by combining the above options
-with the @option{--to-stdout} option (@pxref{Writing to Standard
+with the @value{op-to-stdout} option (@pxref{Writing to Standard
Output}).
If you give the @value{op-verbose} option, then @value{op-extract} will
which you extract, the files from the extracted archive will replace
the files already in the working directory (and possible
subdirectories). This will happen regardless of whether or not the
-files in the working directory were more recent than those extracted.
+files in the working directory were more recent than those extracted
+(there exist, however, special options that alter this behavior
+@pxref{Writing}).
However, if a file was stored with a directory name as part of its file
name, and that directory does not exist under the working directory when
the file is extracted, @command{tar} will create the directory.
-We can demonstrate how to use @samp{--extract} to extract a directory
+We can demonstrate how to use @option{--extract} to extract a directory
file with an example. Change to the @file{practice} directory if you
weren't there, and remove the files @file{folk} and @file{jazz}. Then,
go back to the parent directory and extract the archive
@smallexample
$ @kbd{tar -xvf music.tar practice/folk practice/jazz}
+practice/folk
+practice/jazz
@end smallexample
-@FIXME{need to show tar's response; used verbose above. also, here's a
-good place to demonstrate the -v -v thing. have to write that up
-(should be trivial, but i'm too tired!).}
+@noindent
+If you were to specify two @value{op-verbose} options, @command{tar}
+would have displayed more detail about the extracted files, as shown
+in the example below:
+
+@smallexample
+$ @kbd{tar -xvvf music.tar practice/folk practice/jazz}
+-rw-rw-rw- me user 28 1996-10-18 16:31 practice/jazz
+-rw-rw-rw- me user 20 1996-09-23 16:44 practice/folk
+@end smallexample
@noindent
Because you created the directory with @file{practice} as part of the
$ @kbd{tar -xvf ../untrusted.tar}
@end smallexample
+It is also a good practice to examine contents of the archive
+before extracting it, using @value{op-list} option, possibly combined
+with @value{op-verbose}.
+
@node failing commands
@subsection Commands That Will Fail
If you give the name of a directory as either a file name or a member
name, then @command{tar} acts recursively on all the files and directories
beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @command{tar}.
+the files in the file system to @command{tar}.
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
can be used to specify an option containing whitespace or a backslash.
Note that @command{tar} options are case sensitive. For example, the
-options @samp{-T} and @samp{-t} are different; the first requires an
+options @option{-T} and @option{-t} are different; the first requires an
argument for stating the name of a file providing a list of @var{name}s,
while the second does not require an argument and is another way to
write @value{op-list}.
styles.
@FIXME{menu at end of this node. need to think of an actual outline
-for this chapter; probably do that after stuff from chap. 4 is
+for this chapter; probably do that after stuff from chapter 4 is
incorporated.}
@node Styles
only use the option style(s) which makes the most sense to you until you
feel comfortable with the others.
-@FIXME{hag to write a brief paragraph on the option(s) which can
-optionally take an argument}
+Some options @emph{may} take an argument (currently, there are
+two such options: @value{op-backup} and @value{op-occurrence}). Such
+options may have at most long and short forms, they do not have old style
+equivalent. The rules for specifying an argument for such options
+are stricter than those for specifying mandatory arguments. Please,
+pay special attention to them.
@menu
* Mnemonic Options:: Mnemonic Option Style
@node Mnemonic Options
@subsection Mnemonic Option Style
-@FIXME{have to decide whether or ot to replace other occurrences of
+@FIXME{have to decide whether or not to replace other occurrences of
"mnemonic" with "long", or *ugh* vice versa.}
Each option has at least one long (or mnemonic) name starting with two
-dashes in a row, e.g.@: @samp{--list}. The long names are more clear than
+dashes in a row, e.g., @option{--list}. The long names are more clear than
their corresponding short or old names. It sometimes happens that a
single mnemonic option has many different different names which are
-synonymous, such as @samp{--compare} and @samp{--diff}. In addition,
+synonymous, such as @option{--compare} and @option{--diff}. In addition,
long option names can be given unique abbreviations. For example,
-@samp{--cre} can be used in place of @samp{--create} because there is no
+@option{--cre} can be used in place of @option{--create} because there is no
other mnemonic option which begins with @samp{cre}. (One way to find
this out is by trying it and seeing what happens; if a particular
abbreviation could represent more than one option, @command{tar} will tell
for those not fully acquainted with @command{tar}.
Mnemonic options which require arguments take those arguments
-immediately following the option name; they are introduced by an equal
-sign. For example, the @samp{--file} option (which tells the name
-of the @command{tar} archive) is given a file such as @file{archive.tar}
-as argument by using the notation @samp{--file=archive.tar} for the
-mnemonic option.
+immediately following the option name. There are two ways of
+specifying a mandatory argument. It can be separated from the
+option name either by an equal sign, or by any amount of
+white space characters. For example, the @option{--file} option (which
+tells the name of the @command{tar} archive) is given a file such as
+@file{archive.tar} as argument by using any of the following notations:
+@option{--file=archive.tar} or @option{--file archive.tar}.
+
+In contrast, optional arguments must always be introduced using
+an equal sign. For example, the @option{--backup} option takes
+an optional argument specifying backup type. It must be used
+as @option{--backup=@var{backup-type}}.
@node Short Options
@subsection Short Option Style
Most options also have a short option name. Short options start with
-a single dash, and are followed by a single character, e.g.@: @samp{-t}
-(which is equivalent to @samp{--list}). The forms are absolutely
+a single dash, and are followed by a single character, e.g., @option{-t}
+(which is equivalent to @option{--list}). The forms are absolutely
identical in function; they are interchangeable.
The short option names are faster to type than long option names.
Short options which require arguments take their arguments immediately
following the option, usually separated by white space. It is also
possible to stick the argument right after the short option name, using
-no intervening space. For example, you might write @w{@samp{-f
-archive.tar}} or @samp{-farchive.tar} instead of using
-@samp{--file=archive.tar}. Both @samp{--file=@var{archive-name}} and
-@w{@samp{-f @var{archive-name}}} denote the option which indicates a
+no intervening space. For example, you might write @w{@option{-f
+archive.tar}} or @option{-farchive.tar} instead of using
+@option{--file=archive.tar}. Both @option{--file=@var{archive-name}} and
+@w{@option{-f @var{archive-name}}} denote the option which indicates a
specific archive, here named @file{archive.tar}.
+Short options which take optional arguments take their arguments
+immediately following the option letter, @emph{without any intervening
+white space characters}.
+
Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When
short options are clumped as a set, use one (single) dash for them
-all, e.g.@: @w{@samp{@command{tar} -cvf}}. Only the last option in
+all, e.g., @w{@samp{@command{tar} -cvf}}. Only the last option in
such a set is allowed to have an argument@footnote{Clustering many
options, the last of which has an argument, is a rather opaque way to
write options. Some wonder if @acronym{GNU} @code{getopt} should not
@command{tar} program name and some white space; old options cannot appear
anywhere else. The letter of an old option is exactly the same letter as
the corresponding short option. For example, the old option @samp{t} is
-the same as the short option @samp{-t}, and consequently, the same as the
-mnemonic option @samp{--list}. So for example, the command @w{@samp{tar
-cv}} specifies the option @samp{-v} in addition to the operation @samp{-c}.
+the same as the short option @option{-t}, and consequently, the same as the
+mnemonic option @option{--list}. So for example, the command @w{@samp{tar
+cv}} specifies the option @option{-v} in addition to the operation @option{-c}.
@FIXME{bob suggests having an uglier example. :-) }
@end smallexample
@noindent
-Here, @samp{20} is the argument of @samp{-b} and @samp{/dev/rmt0} is
-the argument of @samp{-f}.
+Here, @samp{20} is the argument of @option{-b} and @samp{/dev/rmt0} is
+the argument of @option{-f}.
On the other hand, this old style syntax makes it difficult to match
option letters with their corresponding arguments, and is often
confusing. In the command @w{@samp{tar cvbf 20 /dev/rmt0}}, for example,
-@samp{20} is the argument for @samp{-b}, @samp{/dev/rmt0} is the
-argument for @samp{-f}, and @samp{-v} does not have a corresponding
+@samp{20} is the argument for @option{-b}, @samp{/dev/rmt0} is the
+argument for @option{-f}, and @option{-v} does not have a corresponding
argument. Even using short options like in @w{@samp{tar -c -v -b 20 -f
/dev/rmt0}} is clearer, putting all arguments next to the option they
pertain to.
are quite different. The first example uses @file{archive.tar.gz} as
the value for option @samp{f} and recognizes the option @samp{z}. The
second example, however, uses @file{z} as the value for option
-@samp{f}---probably not what was intended.
+@samp{f} --- probably not what was intended.
Old options are kept for compatibility with old versions of @command{tar}.
user intended (judging based on the example in the previous set which
uses long options, whose intent is therefore very clear). The first
four specify that the @command{tar} archive would be a file named
-@samp{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
+@option{-c}, @samp{c}, @samp{carchive.tar} or @samp{archive.tarc},
respectively. The first two examples also specify a single non-option,
@var{name} argument having the value @samp{archive.tar}. The last
example contains only old style option letters (repeating option
@node Operation Summary
@subsection Operations
-@table @kbd
+@table @option
@item --append
@itemx -r
@item --catenate
@itemx -A
-Same as @samp{--concatenate}. @xref{concatenate}.
+Same as @option{--concatenate}. @xref{concatenate}.
@item --compare
@itemx -d
@item --diff
@itemx -d
-Same @samp{--compare}. @xref{compare}.
+Same @option{--compare}. @xref{compare}.
@item --extract
@itemx -x
@item --get
@itemx -x
-Same as @samp{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
@item --list
@itemx -t
@item --update
@itemx -u
-@FIXME{It was: A combination of the @samp{--compare} and
-@samp{--append} operations. This is not true and rather misleading,
+@FIXME{It was: A combination of the @option{--compare} and
+@option{--append} operations. This is not true and rather misleading,
as @value{op-compare} does a lot more than @value{op-update} for
ensuring files are identical.} Adds files to the end of the archive,
but only if they are newer than their counterparts already in the
@node Option Summary
@subsection @command{tar} Options
-@table @kbd
+@table @option
@item --absolute-names
@itemx -P
Normally when creating an archive, @command{tar} strips an initial
@samp{/} from member names. This option disables that behavior.
-@FIXME-xref{}
+@xref{absolute}.
@item --after-date
-(See @samp{--newer}.) @FIXME-pxref{}
+(See @option{--newer}.) @FIXME-pxref{}
@item --anchored
An exclude pattern must match an initial subsequence of the name's components.
@FIXME-xref{}
@item --atime-preserve
-
-Tells @command{tar} to preserve the access time field in a file's inode when
-reading it. Due to limitations in the @code{utimes} system call, the
-modification time field is also preserved, which may cause problems if
-the file is simultaneously being modified by another program.
-This option is incompatible with incremental backups, because
-preserving the access time involves updating the last-changed time.
-Also, this option does not work on files that you do not own,
-unless you're root.
-@FIXME-xref{}
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+
+Attempt to preserve the access time of files when reading them. This
+option currently is effective only on files that you own, unless you
+have superuser privileges.
+
+Though this option should work on recent Linux kernel versions, it is
+not reliable on other platforms. To preserve the access time reliably
+on those platforms, you can mount the file system read-only, or access
+the file system via a read-only loopback mount, or use the
+@samp{noatime} mount option available on some systems. However,
+mounting typically requires superuser privileges and can be a pain to
+manage, so the @option{--atime-preserve} option can be useful despite
+its glitches on other platforms.
+
+@value{op-atime-preserve-replace} remembers the access time of a file
+before reading it, and then restores the access time afterwards. This
+may cause problems if other programs are reading the file at the same
+time, as the times of their accesses will be lost. On most platforms
+restoring the access time also requires @command{tar} to restore the
+data modification time too, so this option may also cause problems if
+other programs are writing the file at the same time. (Tar attempts
+to detect this situation, but cannot do so reliably due to race
+conditions.) Worse, on most platforms restoring the access time also
+updates the status change time, which means that this option is
+incompatible with incremental backups.
+
+@value{op-atime-preserve-system} avoids changing time stamps on files
+other than directories, without interfering with time stamp updates
+caused by other programs, so it works better with incremental backups.
+However, it requires a special @code{O_NOATIME} option from the
+underlying operating and file system implementation, and it requires
+that searching directories does not update their access times. As of
+this writing (November 2005) this works only in a few new Linux
+kernels. Worse, there is currently no reliable way to know whether
+the features actually work. Sometimes @command{tar} knows for sure
+that the features are not working, so it will complain and exit right
+away if you try to use @value{op-atime-preserve-system}; but other
+times @command{tar} might think that the option is supported when it
+is not actually working.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@value{op-atime-preserve-replace}, but this may change in the future
+as support for @value{op-atime-preserve-system} improves.
@item --backup=@var{backup-type}
This option directs @command{tar} to print periodic checkpoint messages as it
reads through the archive. Its intended for when you want a visual
indication that @command{tar} is still running, but don't want to see
-@samp{--verbose} output. @FIXME-xref{}
+@option{--verbose} output. @FIXME-xref{}
@item --check-links
@itemx -l
If this option was given, @command{tar} will check the number of links
-dumped for each processed file. If this number does not match the
+dumped for each processed file. If this number does not match the
total number of hard links for the file, a warning message will be
output.
Future versions will take @option{-l} as a short version of
-@option{--check-links}. However, current release still retains the old
+@option{--check-links}. However, current release still retains the old
semantics for @option{-l}.
@xref{Current status}, for more information.
@item --confirmation
-(See @samp{--interactive}.) @FIXME-pxref{}
+(See @option{--interactive}.) @FIXME-pxref{}
@item --dereference
@itemx -h
@item --exclude-from=@var{file}
@itemx -X @var{file}
-Similar to @samp{--exclude}, except @command{tar} will use the list of
+Similar to @option{--exclude}, except @command{tar} will use the list of
patterns in the file @var{file}. @FIXME-xref{}
+@item --exclude-caches
+
+Automatically excludes all directories
+containing a cache directory tag. @FIXME-xref{}
+
@item --file=@var{archive}
@itemx -f @var{archive}
@item --force-local
-Forces @command{tar} to interpret the filename given to @samp{--file}
+Forces @command{tar} to interpret the filename given to @option{--file}
as a local file, even if it looks like a remote tape drive name.
@FIXME-xref{}
@item --format=@var{format}
-Selects output archive format. @var{Format} may be one of the
+Selects output archive format. @var{Format} may be one of the
following:
@table @samp
@item v7
-Tells @command{tar} to create an archive that is compatible with Unix V7
-@command{tar}.
+Creates an archive that is compatible with Unix V7 @command{tar}.
@item oldgnu
-Tells @command{tar} to create an archive that is compatible with GNU
-@command{tar} version 1.12 or earlier.
+Creates an archive that is compatible with GNU @command{tar} version
+1.12 or earlier.
+
+@item gnu
+Creates archive in GNU tar 1.13 format. Basically it is the same as
+@samp{oldgnu} with the only difference in the way it handles long
+numeric fields.
+
+@item ustar
+Creates a @acronym{POSIX.1-1988} compatible archive.
@item posix
-Tells @command{tar} to create POSIX.1-2001 archive.
+Creates a @acronym{POSIX.1-2001 archive}.
-@item gnu
-Tells @command{tar} to create archive in GNU format.
@end table
+@xref{Formats}, for a detailed discussion of these formats.
+
@item --group=@var{group}
Files added to the @command{tar} archive will have a group id of @var{group},
Used to inform @command{tar} that it is working with an old
@acronym{GNU}-format incremental backup archive. It is intended
-primarily for backwards compatibility only. @FIXME-xref{}
+primarily for backwards compatibility only. @FIXME{incremental and
+listed-incremental}.
@item --index-file=@var{file}
performing potentially destructive options, such as overwriting files.
@FIXME-xref{}
+@item --keep-newer-files
+
+Do not replace existing files that are newer than their archive copies
+when extracting files from an archive.
+
@item --keep-old-files
@itemx -k
@item --listed-incremental=@var{snapshot-file}
@itemx -g @var{snapshot-file}
-During a @samp{--create} operation, specifies that the archive that
+During a @option{--create} operation, specifies that the archive that
@command{tar} creates is a new @acronym{GNU}-format incremental
backup, using @var{snapshot-file} to determine which files to backup.
With other operations, informs @command{tar} that the archive is in
-incremental format. @FIXME-xref{}
+incremental format. @FIXME{incremental and listed-incremental}.
@item --mode=@var{permissions}
(see --info-script)
+@item -n
+@itemx --seek
+
+Assume that the archive media supports seeks to arbitrary
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. This option is intended for use
+in cases when such recognition fails.
+
@item --newer=@var{date}
@itemx --after-date=@var{date}
@itemx -N
When creating an archive, @command{tar} will only add files that have changed
since @var{date}. If @var{date} begins with @samp{/} or @samp{.}, it
-is taken to be the name of a file whose last-modified time specifies
+is taken to be the name of a file whose data modification time specifies
the date. @FIXME-xref{}
@item --newer-mtime=@var{date}
-Like @samp{--newer}, but add only files whose
-contents have changed (as opposed to just @samp{--newer}, which will
+Like @option{--newer}, but add only files whose
+contents have changed (as opposed to just @option{--newer}, which will
also back up files for which any status information has changed).
@item --no-anchored
When extracting an archive, do not attempt to preserve the owner
specified in the @command{tar} archive. This the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
@item --no-same-permissions
When extracting an archive, subtract the user's umask from files from
the permissions specified in the archive. This is the default behavior
-for ordinary users; this option has an effect only for the superuser.
+for ordinary users.
@item --no-wildcards
Do not use wildcards when excluding files.
@item --null
-When @command{tar} is using the @samp{--files-from} option, this option
-instructs @command{tar} to expect filenames terminated with @kbd{NUL}, so
+When @command{tar} is using the @option{--files-from} option, this option
+instructs @command{tar} to expect filenames terminated with @option{NUL}, so
@command{tar} can correctly work with file names that contain newlines.
@FIXME-xref{}
@FIXME-xref{}
@item -o
-When extracting files, this option is a synonim for
-@option{--no-same-owner}, i.e. it prevents @command{tar} from
+When extracting files, this option is a synonym for
+@option{--no-same-owner}, i.e. it prevents @command{tar} from
restoring ownership of files being extracted.
-When creating an archive, @option{-o} is a synonim for
-@option{--old-archive}. This behavior is for compatibility
+When creating an archive, @option{-o} is a synonym for
+@option{--old-archive}. This behavior is for compatibility
with previous versions of @GNUTAR{}, and will be
removed in the future releases.
line or via @option{-T} option.
This option instructs @command{tar} to process only the @var{number}th
-occurrence of each named file. @var{Number} defaults to 1, so
+occurrence of each named file. @var{Number} defaults to 1, so
@smallexample
tar -x -f archive.tar --occurrence filename
and will terminate without scanning to the end of the archive.
@item --old-archive
-Synonim for @option{--format=v7}.
+Synonym for @option{--format=v7}.
@item --one-file-system
@itemx -l
directory.
Earlier versions of @GNUTAR{} understood @option{-l} as a
-synonim for @option{--one-file-system}. Although such usage is still
+synonym for @option{--one-file-system}. Although such usage is still
allowed in the present version, it is @emph{strongly discouraged}.
The future versions of @GNUTAR{} will use @option{-l} as
-a synonim for @option{--check-links}.
+a synonym for @option{--check-links}.
@xref{Current status}, for more information.
This option does not affect extraction from archives.
+@item --pax-option=@var{keyword-list}
+
+This option is meaningful only with @acronym{POSIX.1-2001} archives
+(@FIXME-xref{}). It modifies the way @command{tar} handles the
+extended header keywords. @var{Keyword-list} is a comma-separated
+list of keyword options, each keyword option taking one of
+the following forms:
+
+@table @asis
+@item delete=@var{pattern}
+When used with one of archive-creation command (@FIXME-xref{}),
+this option instructs @command{tar} to omit from extended header records
+that it produces any keywords matching the string @var{pattern}.
+
+When used in extract or list mode, this option instructs tar
+to ignore any keywords matching the given @var{pattern} in the extended
+header records. In both cases, matching is performed using the pattern
+matching notation described in @acronym{POSIX 1003.2}, 3.13 @FIXME-xref{see
+man 7 glob}. For example:
+
+@smallexample
+--pax-option delete=security.*
+@end smallexample
+
+would suppress security-related information.
+
+@item exthdr.name=@var{string}
+
+This keyword allows user control over the name that is written into the
+ustar header blocks for the extended headers. The name is obtained
+from @var{string} after substituting the following meta-characters:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %d @tab The directory name of the file, equivalent to the
+result of the @command{dirname} utility on the translated pathname.
+@item %f @tab The filename of the file, equivalent to the result
+of the @command{basename} utility on the translated pathname.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in @var{string} produce undefined
+results.
+
+If no option @samp{exthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+%d/PaxHeaders.%p/%f
+@end smallexample
+
+@item globexthdr.name=@var{string}
+This keyword allows user control over the name that is written into
+the ustar header blocks for global extended header records. The name
+shall will be obtained from the contents of @var{string}, after the
+following character substitutions have been made:
+
+@multitable @columnfractions .30 .70
+@headitem Meta-character @tab Replaced By
+@item %n @tab An integer that represents the
+sequence number of the global extended header record in the archive,
+starting at 1.
+@item %p @tab The process ID of the @command{tar} process.
+@item %% @tab A @samp{%} character.
+@end multitable
+
+Any other @samp{%} characters in string produce undefined results.
+
+If no option @samp{globexthdr.name=string} is specified, @command{tar}
+will use the following default value:
+
+@smallexample
+$TMPDIR/GlobalHead.%p.%n
+@end smallexample
+
+@noindent
+where @samp{$TMPDIR} represents the value of the @var{TMPDIR}
+environment variable. If @var{TMPDIR} is not set, @command{tar}
+uses @samp{/tmp}.
+
+@item @var{keyword}=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included at the beginning of the archive in a global extended
+header record. When used with one of archive-reading commands,
+@command{tar} will behave as if it has encountered these keyword/value
+pairs at the beginning of the archive in a global extended header
+record.
+
+@item @var{keyword}:=@var{value}
+When used with one of archive-creation commands, these keyword/value pairs
+will be included as records at the beginning of an extended header for
+each file. This is effectively equivalent to @var{keyword}=@var{value}
+form except that it creates no global extended header records.
+
+When used with one of archive-reading commands, @command{tar} will
+behave as if these keyword/value pairs were included as records at the
+end of each extended header; thus, they will override any global or
+file-specific extended header record keywords of the same names.
+For example, in the command:
+
+@smallexample
+tar --format=posix --create \
+ --file archive --pax-option gname:=user .
+@end smallexample
+
+the group name will be forced to a new value for all files
+stored in the archive.
+@end table
+
@item --portability
@itemx --old-archive
-Synonim for @option{--format=v7}.
+Synonym for @option{--format=v7}.
@item --posix
Same as @option{--format=posix}.
@item --preserve
-Synonymous with specifying both @samp{--preserve-permissions} and
-@samp{--same-order}. @FIXME-xref{}
+Synonymous with specifying both @option{--preserve-permissions} and
+@option{--same-order}. @FIXME-xref{}
@item --preserve-order
-(See @samp{--same-order}; @pxref{Reading}.)
+(See @option{--same-order}; @pxref{Reading}.)
@item --preserve-permissions
@itemx --same-permissions
Directs @command{tar} to remove the source file from the file system after
appending it to an archive. @FIXME-xref{}
+@item --rmt-command=@var{cmd}
+
+Notifies @command{tar} that it should use @var{cmd} instead of
+the default @file{/usr/libexec/rmt} (@pxref{Remote Tape Server}).
+
@item --rsh-command=@var{cmd}
Notifies @command{tar} that is should use @var{cmd} to communicate with remote
@item --same-permissions
-(See @samp{--preserve-permissions}; @pxref{Writing}.)
+(See @option{--preserve-permissions}; @pxref{Writing}.)
+
+@item --show-defaults
+
+Displays the default options used by @command{tar} and exits
+successfully. This option is intended for use in shell scripts.
+Here is an example of what you can see using this option:
+
+@smallexample
+$ tar --show-defaults
+--format=gnu -f- -b20
+@end smallexample
@item --show-omitted-dirs
Instructs @command{tar} to mention directories its skipping over when
operating on a @command{tar} archive. @FIXME-xref{}
+@item --show-stored-names
+
+This option has effect only when used in conjunction with one of
+archive creation operations. It instructs tar to list the member names
+stored in the archive, as opposed to the actual file
+names. @xref{listing member and file names}.
+
@item --sparse
@itemx -S
files in the archive until it finds one that matches @var{name}.
@xref{Scarce}.
-@item --strip-path=@var{number}
+@item --strip-components=@var{number}
Strip given @var{number} of leading components from file names before
-extraction. For example, if archive @file{archive.tar} contained
+extraction.@footnote{This option was called @option{--strip-path} in
+version 1.14.} For example, if archive @file{archive.tar} contained
@file{/some/file/name}, then running
@smallexample
-tar --extract --file archive.tar --strip-path=2
+tar --extract --file archive.tar --strip-components=2
@end smallexample
@noindent
Specifies the length of tapes that @command{tar} is writing as being
@w{@var{num} x 1024} bytes long. @FIXME-xref{}
+@item --test-label
+
+Reads the volume label. If an argument is specified, test whether it
+matches the volume label. @xref{--test-label option}.
+
@item --to-stdout
@itemx -O
@item --touch
@itemx -m
-Sets the modification time of extracted files to the extraction time,
-rather than the modification time stored in the archive.
+Sets the data modification time of extracted files to the extraction time,
+rather than the data modification time stored in the archive.
@xref{Writing}.
@item --uncompress
-(See @samp{--compress}.) @FIXME-pxref{}
+(See @option{--compress}.) @FIXME-pxref{}
@item --ungzip
-(See @samp{--gzip}.) @FIXME-pxref{}
+(See @option{--gzip}.) @FIXME-pxref{}
@item --unlink-first
@itemx -U
Instructs @command{tar} to access the archive through @var{prog}, which is
presumed to be a compression program of some sort. @FIXME-xref{}
+@item --utc
+
+Display file modification dates in @acronym{UTC}. This option implies
+@option{--verbose}.
+
@item --verbose
@itemx -v
@item --volno-file=@var{file}
-Used in conjunction with @samp{--multi-volume}. @command{tar} will keep track
+Used in conjunction with @option{--multi-volume}. @command{tar} will keep track
of which volume of a multi-volume archive its working in @var{file}.
@FIXME-xref{}
Here is an alphabetized list of all of the short option forms, matching
them with the equivalent long option.
-@table @kbd
+@table @option
@item -A
-@samp{--concatenate}
+@option{--concatenate}
@item -B
-@samp{--read-full-records}
+@option{--read-full-records}
@item -C
-@samp{--directory}
+@option{--directory}
@item -F
-@samp{--info-script}
+@option{--info-script}
@item -G
-@samp{--incremental}
+@option{--incremental}
@item -K
-@samp{--starting-file}
+@option{--starting-file}
@item -L
-@samp{--tape-length}
+@option{--tape-length}
@item -M
-@samp{--multi-volume}
+@option{--multi-volume}
@item -N
-@samp{--newer}
+@option{--newer}
@item -O
-@samp{--to-stdout}
+@option{--to-stdout}
@item -P
-@samp{--absolute-names}
+@option{--absolute-names}
@item -R
-@samp{--block-number}
+@option{--block-number}
@item -S
-@samp{--sparse}
+@option{--sparse}
@item -T
-@samp{--files-from}
+@option{--files-from}
@item -U
-@samp{--unlink-first}
+@option{--unlink-first}
@item -V
-@samp{--label}
+@option{--label}
@item -W
-@samp{--verify}
+@option{--verify}
@item -X
-@samp{--exclude-from}
+@option{--exclude-from}
@item -Z
-@samp{--compress}
+@option{--compress}
@item -b
-@samp{--blocking-factor}
+@option{--blocking-factor}
@item -c
-@samp{--create}
+@option{--create}
@item -d
-@samp{--compare}
+@option{--compare}
@item -f
-@samp{--file}
+@option{--file}
@item -g
-@samp{--listed-incremental}
+@option{--listed-incremental}
@item -h
-@samp{--dereference}
+@option{--dereference}
@item -i
-@samp{--ignore-zeros}
+@option{--ignore-zeros}
@item -j
-@samp{--bzip2}
+@option{--bzip2}
@item -k
-@samp{--keep-old-files}
+@option{--keep-old-files}
@item -l
-@samp{--one-file-system}. Use of this short option is deprecated. It
+@option{--one-file-system}. Use of this short option is deprecated. It
is retained for compatibility with the earlier versions of GNU
@command{tar}, and will be changed in future releases.
@item -m
-@samp{--touch}
+@option{--touch}
@item -o
-When creating --- @samp{--no-same-owner}, when extracting ---
-@samp{--portability}.
+When creating --- @option{--no-same-owner}, when extracting ---
+@option{--portability}.
-The later usage is deprecated. It is retained for compatibility with
-the earlier versions of @GNUTAR{}. In the future releases
-@option{-o} will be equivalent to @samp{--no-same-owner} only.
+The later usage is deprecated. It is retained for compatibility with
+the earlier versions of @GNUTAR{}. In the future releases
+@option{-o} will be equivalent to @option{--no-same-owner} only.
@item -p
-@samp{--preserve-permissions}
+@option{--preserve-permissions}
@item -r
-@samp{--append}
+@option{--append}
@item -s
-@samp{--same-order}
+@option{--same-order}
@item -t
-@samp{--list}
+@option{--list}
@item -u
-@samp{--update}
+@option{--update}
@item -v
-@samp{--verbose}
+@option{--verbose}
@item -w
-@samp{--interactive}
+@option{--interactive}
@item -x
-@samp{--extract}
+@option{--extract}
@item -z
-@samp{--gzip}
+@option{--gzip}
@end table
@smallexample
$ @kbd{tar --extract --file=archive.tar --verbose --verbose}
-$ @kbd{tar xvv archive.tar}
+$ @kbd{tar xvvf archive.tar}
@end smallexample
Verbose output appears on the standard output except when an archive is
amount written to the archive, after it has been fully created.
The @value{op-checkpoint} option prints an occasional message
-as @command{tar} reads or writes the archive. In fact, it print
-directory names while reading the archive. It is designed for
+as @command{tar} reads or writes the archive. In fact, it prints
+a message each 10 records read or written. It is designed for
those who don't need the more detailed (and voluminous) output of
@value{op-block-number}, but do want visual confirmation that @command{tar}
is actually making forward progress.
if disk or storage space is tight). You can do this by excluding
certain files automatically (@pxref{Choosing}), or by performing
an operation interactively, using the @value{op-interactive} option.
-@command{tar} also accepts @samp{--confirmation} for this option.
+@command{tar} also accepts @option{--confirmation} for this option.
When the @value{op-interactive} option is specified, before
reading, writing, or deleting files, @command{tar} first prints a message
@item
Mistakingly using @code{create} instead of @code{extract}, when the
intent was to extract the full contents of an archive. This error
-is likely: keys @kbd{c} and @kbd{x} are right next ot each other on
+is likely: keys @kbd{c} and @kbd{x} are right next to each other on
the QWERTY keyboard. Instead of being unpacked, the archive then
gets wholly destroyed. When users speak about @dfn{exploding} an
archive, they usually mean something else :-).
In the last chapter, you learned about the first three operations to
@command{tar}. This chapter presents the remaining five operations to
-@command{tar}: @samp{--append}, @samp{--update}, @samp{--concatenate},
-@samp{--delete}, and @samp{--compare}.
+@command{tar}: @option{--append}, @option{--update}, @option{--concatenate},
+@option{--delete}, and @option{--compare}.
You are not likely to use these operations as frequently as those
covered in the last chapter; however, since they perform specialized
The five operations that we will cover in this chapter are:
-@table @kbd
+@table @option
@item --append
@itemx -r
Add new entries to an archive that already exists.
@end table
@node append
-@subsection How to Add Files to Existing Archives: @code{--append}
+@subsection How to Add Files to Existing Archives: @option{--append}
@UNREVISED
If you want to add files to an existing archive, you don't need to
create a new archive; you can use @value{op-append}. The archive must
-already exist in order to use @samp{--append}. (A related operation
-is the @samp{--update} operation; you can use this to add newer
+already exist in order to use @option{--append}. (A related operation
+is the @option{--update} operation; you can use this to add newer
versions of archive members to an existing archive. To learn how to
-do this with @samp{--update}, @pxref{update}.)
-
-@FIXME{Explain in second paragraph whether you can get to the previous
-version -- explain whole situation somewhat more clearly.}
+do this with @option{--update}, @pxref{update}.)
If you use @value{op-append} to add a file that has the same name as an
archive member to an archive containing that archive member, then the
old member is not deleted. What does happen, however, is somewhat
-complex. @command{tar} @emph{allows} you to have infinite numbers of files
+complex. @command{tar} @emph{allows} you to have infinite number of files
with the same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
view an archive with @value{op-list}, you will see all of those members
-listed, with their modification times, owners, etc.
+listed, with their data modification times, owners, etc.
Other operations don't deal with these members as perfectly as you might
prefer; if you were to use @value{op-extract} to extract the archive,
only the most recently added copy of a member with the same name as four
other members would end up in the working directory. This is because
-@samp{--extract} extracts an archive in the order the members appeared
+@option{--extract} extracts an archive in the order the members appeared
in the archive; the most recently archived members will be extracted
last. Additionally, an extracted member will @emph{replace} a file of
the same name which existed in the directory already, and @command{tar}
-will not prompt you about this. Thus, only the most recently archived
+will not prompt you about this@footnote{Unless you give it
+@option{--keep-old-files} option, or the disk copy is newer than the
+the one in the archive and you invoke @command{tar} with
+@option{--keep-newer-files} option}. Thus, only the most recently archived
member will end up being extracted, as it will replace the one
extracted before it, and so on.
+There exists a special option that allows you to get around this
+behavior and extract (or list) only a particular copy of the file.
+This is @option{--occurrence} option. If you run @command{tar} with
+this option, it will extract only the first copy of the file. You
+may also give this option an argument specifying the number of
+copy to be extracted. Thus, for example if the archive
+@file{archive.tar} contained three copies of file @file{myfile}, then
+the command
+
+@smallexample
+tar --extract --file archive.tar --occurrence=2 myfile
+@end smallexample
+
+@noindent
+would extract only the second copy. @xref{Option Summary,---occurrence}, for the description of @value{op-occurrence} option.
+
@FIXME{ hag -- you might want to incorporate some of the above into the
-MMwtSN node; not sure. i didn't know how to make it simpler...}
+MMwtSN node; not sure. i didn't know how to make it simpler...
-There are a few ways to get around this. @FIXME-xref{Multiple Members
+There are a few ways to get around this. (maybe xref Multiple Members
with the Same Name.}
@cindex Members, replacing with other members
@cindex Replacing members with other members
If you want to replace an archive member, use @value{op-delete} to
delete the member you want to remove from the archive, , and then use
-@samp{--append} to add the member you want to be in the archive. Note
+@option{--append} to add the member you want to be in the archive. Note
that you can not change the order of the archive; the most recently
added member will still appear last. In this sense, you cannot truly
``replace'' one member with another. (Replacing one member with another
The simplest way to add a file to an already existing archive is the
@value{op-append} operation, which writes specified files into the
archive whether or not they are already among the archived files.
-When you use @samp{--append}, you @emph{must} specify file name
+When you use @option{--append}, you @emph{must} specify file name
arguments, as there is no default. If you specify a file that already
exists in the archive, another copy of the file will be added to the
end of the archive. As with other operations, the member names of the
command line. The @value{op-verbose} option will print out the names
of the files as they are written into the archive.
-@samp{--append} cannot be performed on some tape drives, unfortunately,
+@option{--append} cannot be performed on some tape drives, unfortunately,
due to deficiencies in the formats those tape drives use. The archive
must be a valid @command{tar} archive, or else the results of using this
operation will be unpredictable. @xref{Media}.
-To demonstrate using @samp{--append} to add a file to an archive,
+To demonstrate using @option{--append} to add a file to an archive,
create a file called @file{rock} in the @file{practice} directory.
Make sure you are in the @file{practice} directory. Then, run the
following @command{tar} command to add @file{rock} to
You can use @value{op-append} to add copies of files which have been
updated since the archive was created. (However, we do not recommend
doing this since there is another @command{tar} option called
-@samp{--update}; @pxref{update} for more information. We describe this
-use of @samp{--append} here for the sake of completeness.) @FIXME{is
+@option{--update}; @pxref{update} for more information. We describe this
+use of @option{--append} here for the sake of completeness.) @FIXME{is
this really a good idea, to give this whole description for something
which i believe is basically a Stupid way of doing something? certain
aspects of it show ways in which tar is more broken than i'd personally
like to admit to, specifically the last sentence. On the other hand, i
-don't think it's a good idea to be saying that re explicitly don't
+don't think it's a good idea to be saying that we explicitly don't
recommend using something, but i can't see any better way to deal with
the situation.}When you extract the archive, the older version will be
effectively lost. This works because files are extracted from an
@end smallexample
@noindent
-Because you specified the @samp{--verbose} option, @command{tar} has
+Because you specified the @option{--verbose} option, @command{tar} has
printed the name of the file being appended as it was acted on. Now
list the contents of the archive:
(note the different creation dates and file sizes). If you extract
the archive, the older version of the file @file{blues} will be
replaced by the newer version. You can confirm this by extracting
-the archive and running @samp{ls} on the directory. @xref{Writing},
-for more information. (@emph{Please note:} This is the case unless
-you employ the @value{op-backup} option. @FIXME-ref{Multiple Members
-with the Same Name}.)
+the archive and running @samp{ls} on the directory.
+
+If you wish to extract the first occurrence of the file @file{blues}
+from the archive, use @value{op-occurrence} option, as shown in
+the following example:
+
+@smallexample
+$ @kbd{tar --extract -vv --occurrence --file=collection.tar blues}
+-rw-rw-rw- me user 21 1996-09-23 16:44 blues
+@end smallexample
+
+@xref{Writing}, for more information on @value{op-extract} and
+@xref{Option Summary, --occurrence}, for the description of
+@value{op-occurrence} option.
@node update
@subsection Updating an Archive
In the previous section, you learned how to use @value{op-append} to add
a file to an existing archive. A related operation is
-@value{op-update}. The @samp{--update} operation updates a @command{tar}
+@value{op-update}. The @option{--update} operation updates a @command{tar}
archive by comparing the date of the specified archive members against
the date of the file with the same name. If the file has been modified
more recently than the archive member, then the newer version of the
file is added to the archive (as with @value{op-append}).
-Unfortunately, you cannot use @samp{--update} with magnetic tape drives.
+Unfortunately, you cannot use @option{--update} with magnetic tape drives.
The operation will fail.
@FIXME{other examples of media on which --update will fail? need to ask
charles and/or mib/thomas/dave shevett..}
-Both @samp{--update} and @samp{--append} work by adding to the end
+Both @option{--update} and @option{--append} work by adding to the end
of the archive. When you extract a file from the archive, only the
version stored last will wind up in the file system, unless you use
-the @value{op-backup} option. @FIXME-ref{Multiple Members with the
+the @value{op-backup} option. @FIXME-ref{Multiple Members with the
Same Name}
@menu
@end menu
@node how to update
-@subsubsection How to Update an Archive Using @code{--update}
+@subsubsection How to Update an Archive Using @option{--update}
You must use file name arguments with the @value{op-update} operation.
If you don't specify any files, @command{tar} won't act on any files and
@FIXME{note: the above parenthetical added because in fact, this
behavior just confused the author. :-) }
-To see the @samp{--update} option at work, create a new file,
+To see the @option{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
file @file{blues}, using any text editor. Then invoke @command{tar} with
the @samp{update} operation and the @value{op-verbose} option specified,
efficient. If you need to run backups, please consult @ref{Backups}.
@node concatenate
-@subsection Combining Archives with @code{--concatenate}
+@subsection Combining Archives with @option{--concatenate}
@cindex Adding archives to an archive
@cindex Concatenating Archives
one or more archives to the end of another archive, you should use the
@value{op-concatenate} operation.
-To use @samp{--concatenate}, name the archives to be concatenated on the
+To use @option{--concatenate}, name the archives to be concatenated on the
command line. (Nothing happens if you don't list any.) The members,
and their member names, will be copied verbatim from those archives. If
this causes multiple members to have the same name, it does not delete
information on how this affects reading the archive, Multiple
Members with the Same Name.}
-To demonstrate how @samp{--concatenate} works, create two small archives
+To demonstrate how @option{--concatenate} works, create two small archives
called @file{bluesrock.tar} and @file{folkjazz.tar}, using the relevant
files from @file{practice}:
folk
@end smallexample
-When you use @samp{--concatenate}, the source and target archives must
+When you use @option{--concatenate}, the source and target archives must
already exist and must have been created using compatible format
parameters. @FIXME-pxref{Matching Format Parameters}The new,
concatenated archive will be called by the same name as the first
-archive listed on the command line. @FIXME{is there a way to specify a
+archive listed on the command line. @FIXME{is there a way to specify a
new name?}
Like @value{op-append}, this operation cannot be performed on some
@cindex @code{concatenate} vs @command{cat}
@cindex @command{cat} vs @code{concatenate}
It may seem more intuitive to you to want or try to use @command{cat} to
-concatenate two archives instead of using the @samp{--concatenate}
+concatenate two archives instead of using the @option{--concatenate}
operation; after all, @command{cat} is the utility for combining files.
However, @command{tar} archives incorporate an end-of-file marker which
must be removed if the concatenated archives are to be read properly as
-one archive. @samp{--concatenate} removes the end-of-archive marker
+one archive. @option{--concatenate} removes the end-of-archive marker
from the target archive before each new archive is appended. If you use
@command{cat} to combine the archives, the result will not be a valid
@command{tar} format archive. If you need to retrieve files from an
default archive name.
@node delete
-@subsection Removing Archive Members Using @samp{--delete}
+@subsection Removing Archive Members Using @option{--delete}
@UNREVISED
@cindex Deleting files from an archive
@cindex Removing files from an archive
names, nothing will be deleted. The @value{op-verbose} option will
cause @command{tar} to print the names of the members as they are deleted.
As with @value{op-extract}, you must give the exact member names when
-using @samp{tar --delete}. @samp{--delete} will remove all versions of
-the named file from the archive. The @samp{--delete} operation can run
+using @samp{tar --delete}. @option{--delete} will remove all versions of
+the named file from the archive. The @option{--delete} operation can run
very slowly.
-Unlike other operations, @samp{--delete} has no short form.
+Unlike other operations, @option{--delete} has no short form.
-@cindex Tapes, using @code{--delete} and
+@cindex Tapes, using @option{--delete} and
@cindex Deleting from tape archives
This operation will rewrite the archive. You can only use
-@samp{--delete} on an archive if the archive device allows you to
+@option{--delete} on an archive if the archive device allows you to
write to any point on the media, such as a disk; because of this, it
does not work on magnetic tapes. Do not try to delete an archive member
from a magnetic tape; the action will not succeed, and you will be
@cindex Verifying the currency of an archive
@UNREVISED
-The @samp{--compare} (@samp{-d}), or @samp{--diff} operation compares
+The @option{--compare} (@option{-d}), or @option{--diff} operation compares
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should @emph{only} specify archive member names, not file
the integrity of the archive media. For this later goal, @xref{verify}.
@node create options
-@section Options Used by @code{--create}
+@section Options Used by @option{--create}
The previous chapter described the basics of how to use
@value{op-create} to create an archive from a set of files.
@xref{create}. This section described advanced options to be used with
-@samp{--create}.
+@option{--create}.
@menu
* Ignore Failed Read::
@node Ignore Failed Read
@subsection Ignore Fail Read
-@table @kbd
+@table @option
@item --ignore-failed-read
Do not exit with nonzero on unreadable files or directories.
@end table
@node extract options
-@section Options Used by @code{--extract}
+@section Options Used by @option{--extract}
@UNREVISED
@FIXME{i need to get dan to go over these options with me and see if
there's a better way of organizing them.}
The previous chapter showed how to use @value{op-extract} to extract
-an archive into the filesystem. Various options cause @command{tar} to
+an archive into the file system. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
-presents options to be used with @samp{--extract} when certain special
+presents options to be used with @option{--extract} when certain special
considerations arise. You may review the information presented in
@ref{extract} for more basic information about the
-@samp{--extract} operation.
+@option{--extract} operation.
@menu
* Reading:: Options to Help Read Archives
@FIXME{need sentence or so of intro here}
-@table @kbd
+@table @option
@item --read-full-records
@item -B
Use in conjunction with @value{op-extract} to read an archive which
Normally, @command{tar} stops reading when it encounters a block of zeros
between file entries (which usually indicates the end of the archive).
@value{op-ignore-zeros} allows @command{tar} to completely read an archive
-which contains a block of zeros before the end (i.e.@: a damaged
-archive, or one which was created by concatenating several archives
+which contains a block of zeros before the end (i.e., a damaged
+archive, or one that was created by concatenating several archives
together).
The @value{op-ignore-zeros} option is turned off by default because many
does not write after the end of an archive, but seeks to
maintain compatiblity among archiving utilities.
-@table @kbd
+@table @option
@item --ignore-zeros
@itemx -i
-To ignore blocks of zeros (ie.@: end-of-archive entries) which may be
+To ignore blocks of zeros (i.e., end-of-archive entries) which may be
encountered while reading an archive. Use in conjunction with
@value{op-extract} or @value{op-list}.
@end table
@subsection Changing How @command{tar} Writes Files
@cindex Overwriting old files, prevention
@cindex Protecting old files
+@cindex Data modification times of extracted files
@cindex Modification times of extracted files
@cindex Permissions of extracted files
@cindex Modes of extracted files
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
Some people argue that @GNUTAR{} should not hesitate
to overwrite files with other files when extracting. When extracting
a @command{tar} archive, they expect to see a faithful copy of the
-state of the filesystem when the archive was created. It is debatable
+state of the file system when the archive was created. It is debatable
that this would always be a proper behavior. For example, suppose one
has an archive in which @file{usr/local} is a link to
@file{usr/local2}. Since then, maybe the site removed the link and
not be welcome at all that @GNUTAR{} removes the
whole hierarchy just to make room for the link to be reinstated
(unless it @emph{also} simultaneously restores the full
-@file{/usr/local2}, of course! @GNUTAR{} is indeed
+@file{/usr/local2}, of course!) @GNUTAR{} is indeed
able to remove a whole hierarchy to reestablish a symbolic link, for
example, but @emph{only if} @value{op-recursive-unlink} is specified
to allow this behavior. In any case, single files are silently
@node Overwrite Old Files
@unnumberedsubsubsec Overwrite Old Files
-@table @kbd
+@table @option
@item --overwrite
Overwrite existing files and directory metadata when extracting files
from an archive.
@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
-@table @kbd
+@table @option
@item --keep-old-files
@itemx -k
Do not replace existing files from archive. The
extraction.
@end table
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @option
+@item --keep-newer-files
+Do not replace existing files that are newer than their archive
+copies. This option is meaningless with @value{op-list}.
+@end table
+
@node Unlink First
@unnumberedsubsubsec Unlink First
-@table @kbd
+@table @option
@item --unlink-first
@itemx -U
Remove files before extracting over them.
@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
-@table @kbd
+@table @option
@item --recursive-unlink
When this option is specified, try removing files and directory hierarchies
before extracting over them. @emph{This is a dangerous option!}
as far as current permissions will allow it. This could include removal
of the contents of a full directory hierarchy.
-@node Modification Times
-@unnumberedsubsubsec Setting Modification Times
+@node Data Modification Times
+@unnumberedsubsubsec Setting Data Modification Times
-Normally, @command{tar} sets the modification times of extracted files to
-the modification times recorded for the files in the archive, but
+Normally, @command{tar} sets the data modification times of extracted
+files to the corresponding times recorded for the files in the archive, but
limits the permissions of extracted files by the current @code{umask}
setting.
-To set the modification times of extracted files to the time when
+To set the data modification times of extracted files to the time when
the files were extracted, use the @value{op-touch} option in
conjunction with @value{op-extract}.
-@table @kbd
+@table @option
@item --touch
@itemx -m
-Sets the modification time of extracted archive members to the time
+Sets the data modification time of extracted archive members to the time
they were extracted, not the time recorded for them in the archive.
Use in conjunction with @value{op-extract}.
@end table
@unnumberedsubsubsec Setting Access Permissions
To set the modes (access permissions) of extracted files to those
-recorded for those files in the archive, use @samp{--same-permissions}
+recorded for those files in the archive, use @option{--same-permissions}
in conjunction with the @value{op-extract} operation. @FIXME{Should be
aliased to ignore-umask.}
-@table @kbd
+@table @option
@item --preserve-permission
@itemx --same-permission
@itemx --ignore-umask
they appear on standard output concatenated, in the order they are
found in the archive.
-@table @kbd
+@table @option
@item --to-stdout
@itemx -O
Writes files to the standard output. Used in conjunction with
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
-@table @kbd
+@table @option
@item --remove-files
Remove files after adding them to the archive.
@end table
@node Starting File
@unnumberedsubsubsec Starting File
-@table @kbd
+@table @option
@item --starting-file=@var{name}
@itemx -K @var{name}
Starts an operation in the middle of an archive. Use in conjunction
@node Same Order
@unnumberedsubsubsec Same Order
-@table @kbd
+@table @option
@item --same-order
@itemx --preserve-order
@itemx -s
@opindex --suffix
@cindex backup suffix
@vindex SIMPLE_BACKUP_SUFFIX
-Append @var{suffix} to each backup file made with @samp{--backup}. If this
+Append @var{suffix} to each backup file made with @option{--backup}. If this
option is not specified, the value of the @env{SIMPLE_BACKUP_SUFFIX}
environment variable is used. And if @env{SIMPLE_BACKUP_SUFFIX} is not
set, the default is @samp{~}, just as in Emacs.
medium is a @dfn{pipe}, which is one a Unix redirection mechanism:
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
@end smallexample
@noindent
The command also works using short option forms:
-@FIXME{The following using standard input/output correct??}
@smallexample
-$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
+$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
@end smallexample
@noindent
arguments to @command{tar} (this can help you save time if you expect to
archive the same list of files a number of times), and so forth.
@FIXME{in case it's not obvious, i'm making this up in some sense
-based on my imited memory of what the next chapter *really* does. i
+based on my limited memory of what the next chapter *really* does. i
just wanted to flesh out this final section a little bit so i'd
-remember to sitck it in here. :-)}
+remember to stick it in here. :-)}
If there are too many files to conveniently list on the command line,
you can list the names in a file, and @command{tar} will read that file.
ftp://ftp.cs.umd.edu/pub/amanda
@end smallexample
-@ifclear PUBLISH
+@FIXME{
Here is a possible plan for a future documentation about the backuping
scripts which are provided within the @GNUTAR{}
distribution.
-@smallexample
-.* dumps
-. + what are dumps
-
-. + different levels of dumps
-. - full dump = dump everything
-. - level 1, level 2 dumps etc, -
- A level n dump dumps everything changed since the last level
- n-1 dump (?)
-
-. + how to use scripts for dumps (ie, the concept)
-. - scripts to run after editing backup specs (details)
-
-. + Backup Specs, what is it.
-. - how to customize
-. - actual text of script [/sp/dump/backup-specs]
-
-. + Problems
-. - rsh doesn't work
-. - rtape isn't installed
-. - (others?)
-
-. + the --incremental option of tar
-
-. + tapes
-. - write protection
-. - types of media
-. : different sizes and types, useful for different things
-. - files and tape marks
+@itemize @bullet
+@item dumps
+ @itemize @minus
+ @item what are dumps
+ @item different levels of dumps
+ @itemize +
+ @item full dump = dump everything
+ @item level 1, level 2 dumps etc
+ A level @var{n} dump dumps everything changed since the last level
+ @var{n}-1 dump (?)
+ @end itemize
+ @item how to use scripts for dumps (ie, the concept)
+ @itemize +
+ @item scripts to run after editing backup specs (details)
+ @end itemize
+ @item Backup Specs, what is it.
+ @itemize +
+ @item how to customize
+ @item actual text of script [/sp/dump/backup-specs]
+ @end itemize
+ @item Problems
+ @itemize +
+ @item rsh doesn't work
+ @item rtape isn't installed
+ @item (others?)
+ @end itemize
+ @item the @option{--incremental} option of tar
+ @item tapes
+ @itemize +
+ @item write protection
+ @item types of media, different sizes and types, useful for different things
+ @item files and tape marks
one tape mark between files, two at end.
-. - positioning the tape
+ @item positioning the tape
MT writes two at end of write,
- backspaces over one when writing again.
-@end smallexample
-
-@end ifclear
+ backspaces over one when writing again.
+ @end itemize
+ @end itemize
+@end itemize
+}
-This chapter documents both the provided FSF scripts and @command{tar}
+This chapter documents both the provided shell scripts and @command{tar}
options which are more specific to usage as a backup tool.
To @dfn{back up} a file system means to create archives that contain
@menu
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
@cindex corrupted archives
Full dumps should only be made when no other people or programs
-are modifying files in the filesystem. If files are modified while
+are modifying files in the file system. If files are modified while
@command{tar} is making the backup, they may not be stored properly in
the archive, in which case you won't be able to restore them if you
have to. (Files not being modified are written with no trouble, and do
volume label, so you can tell what this archive is even if the label
falls off the tape, or anything like that.
-Unless the filesystem you are dumping is guaranteed to fit on
+Unless the file system you are dumping is guaranteed to fit on
one volume, you will need to use the @value{op-multi-volume} option.
Make sure you have enough tapes on hand to complete the backup.
-If you want to dump each filesystem separately you will need to use
+If you want to dump each file system separately you will need to use
the @value{op-one-file-system} option to prevent @command{tar} from crossing
-filesystem boundaries when storing (sub)directories.
+file system boundaries when storing (sub)directories.
-The @value{op-incremental} option is not needed, since this is a complete
-copy of everything in the filesystem, and a full restore from this
-backup would only be done onto a completely empty disk.
+The @value{op-incremental} (@FIXME-pxref{}) option is not needed,
+since this is a complete copy of everything in the file system, and a
+full restore from this backup would only be done onto a completely
+empty disk.
Unless you are in a hurry, and trust the @command{tar} program (and your
tapes), it is a good idea to use the @value{op-verify} option, to make
it was being archived. Not all media (notably cartridge tapes) are
capable of being verified, unfortunately.
-@value{op-listed-incremental} take a file name argument always. If the
-file doesn't exist, run a level zero dump, creating the file. If the
-file exists, uses that file to see what has changed.
-
-@value{op-incremental} @FIXME{look it up}
-
-@value{op-incremental} handle old @acronym{GNU}-format incremental backup.
+@node Incremental Dumps
+@section Using @command{tar} to Perform Incremental Dumps
-This option should only be used when creating an incremental backup of
-a filesystem. When the @value{op-incremental} option is used, @command{tar}
-writes, at the beginning of the archive, an entry for each of the
-directories that will be operated on. The entry for a directory
-includes a list of all the files in the directory at the time the
-dump was done, and a flag for each file indicating whether the file
-is going to be put in the archive. This information is used when
-doing a complete incremental restore.
+@dfn{Incremental backup} is a special form of @GNUTAR{} archive that
+stores additional metadata so that exact state of the file system
+can be restored when extracting the archive.
-Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@acronym{GNU} versions of the
-@command{tar} program.
+@GNUTAR{} currently offers two options for handling incremental
+backups: @value{op-listed-incremental} and @value{op-incremental}.
-The @value{op-incremental} option means the archive is an incremental
-backup. Its meaning depends on the command that it modifies.
+The option @option{--listed-incremental} instructs tar to operate on
+an incremental archive with additional metadata stored in a standalone
+file, called a @dfn{snapshot file}. The purpose of this file is to help
+determine which files have been changed, added or deleted since the
+last backup, so that the next incremental backup will contain only
+modified files. The name of the snapshot file is given as an argument
+to the option:
-If the @value{op-incremental} option is used with @value{op-list},
-@command{tar} will list, for each directory in the archive, the list
-of files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is
-followed by an additional null and a newline to indicate the end of
-the data.
-
-If the @value{op-incremental} option is used with @value{op-extract}, then
-when the entry for a directory is found, all files that currently
-exist in that directory but are not listed in the archive @emph{are
-deleted from the directory}.
-
-This behavior is convenient when you are restoring a damaged file
-system from a succession of incremental backups: it restores the
-entire state of the file system to that which obtained when the backup
-was made. If you don't use @value{op-incremental}, the file system will
-probably fill up with files that shouldn't exist any more.
-
-@value{op-listed-incremental} handle new @acronym{GNU}-format
-incremental backup. This option handles new @acronym{GNU}-format
-incremental backup. It has much the same effect as
-@value{op-incremental}, but also the time when the dump is done and
-the list of directories dumped is written to the given
-@var{file}. When restoring, only files newer than the saved time are
-restored, and the directory list is used to speed up operations.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar} to
-use the file @var{file}, which contains information about the state
-of the filesystem at the time of the last backup, to decide which
-files to include in the archive being created. That file will then
-be updated by @command{tar}. If the file @var{file} does not exist when
-this option is specified, @command{tar} will create it, and include all
-appropriate files in the archive.
-
-The file, which is archive independent, contains the date it was last
-modified and a list of devices, inode numbers and directory names.
-@command{tar} will archive files with newer mod dates or inode change
-times, and directories with an unchanged inode number and device but
-a changed directory name. The file is updated after the files to
-be archived are determined, but before the new archive is actually
-created.
-
-@node Inc Dumps
-@section Using @command{tar} to Perform Incremental Dumps
-@UNREVISED
+@table @option
+@item --listed-incremental=@var{file}
+@itemx -g @var{file}
+ Handle incremental backups with snapshot data in @var{file}.
+@end table
-@cindex incremental dumps
-@cindex dumps, incremental
+To create an incremental backup, you would use
+@option{--listed-incremental} together with @option{--create}
+(@pxref{create}). For example:
-Performing incremental dumps is similar to performing full dumps,
-although a few more options will usually be needed.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.1.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+@end smallexample
-A standard scheme is to do a @emph{monthly} (full) dump once a month,
-a @emph{weekly} dump once a week of everything since the last monthly
-and a @emph{daily} every day of everything since the last (weekly or
-monthly) dump.
+This will create in @file{archive.1.tar} an incremental backup of
+the @file{/usr} file system, storing additional metadata in the file
+@file{/var/log/usr.snar}. If this file does not exist, it will be
+created. The created archive will then be a @dfn{level 0 backup};
+please see the next section for more on backup levels.
-Here is a sample script to dump the directory hierarchies @samp{/usr}
-and @samp{/var}.
+Otherwise, if the file @file{/var/log/usr.snar} exists, it
+determines which files are modified. In this case only these files will be
+stored in the archive. Suppose, for example, that after running the
+above command, you delete file @file{/usr/doc/old} and create
+directory @file{/usr/local/db} with the following contents:
@smallexample
-#! /bin/sh
-tar --create \
- --blocking-factor=126 \
- --file=/dev/rmt/0 \
- --label="`hostname` /usr /var `date +%Y-%m-%d`" \
- --listed-incremental=/var/log/usr-var.snar \
- --verbose \
- /usr /var
+$ @kbd{ls /usr/local/db}
+/usr/local/db/data
+/usr/local/db/index
@end smallexample
-This script uses the file @file{/var/log/usr-var.snar} as a snapshot to
-store information about the previous tar dump.
+Some time later you create another incremental backup. You will
+then see:
-The blocking factor 126 is an attempt to make the tape drive stream.
-Some tape devices cannot handle 64 kB blocks or larger, and require the
-block size to be a multiple of 1 kB; for these devices, 126 is the
-largest blocking factor that can be used.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+tar: usr/local/db: Directory is new
+usr/local/db/
+usr/local/db/data
+usr/local/db/index
+@end smallexample
-@node incremental and listed-incremental
-@section The Incremental Options
-@UNREVISED
+@noindent
+The created archive @file{archive.2.tar} will contain only these
+three members. This archive is called a @dfn{level 1 backup}. Notice
+that @file{/var/log/usr.snar} will be updated with the new data, so if
+you plan to create more @samp{level 1} backups, it is necessary to
+create a working copy of the snapshot file before running
+@command{tar}. The above example will then be modified as follows:
-@value{op-incremental} is used in conjunction with @value{op-create},
-@value{op-extract} or @value{op-list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@value{op-incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@value{op-listed-incremental}, which is described below.
-
-@value{op-incremental} in conjunction with @value{op-create} causes
-@command{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@acronym{GNU} versions of the
-@command{tar} program.
-
-@value{op-incremental} in conjunction with @value{op-extract} causes
-@command{tar} to read the lists of directory contents previously stored
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
-
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@value{op-incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
-
-@value{op-incremental} in conjunction with @value{op-list} causes
-@command{tar} to print, for each directory in the archive, the list of
-files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is followed
-by an additional null and a newline to indicate the end of the data.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar}
-to use the file @var{snapshot-file}, which contains information about
-the state of the file system at the time of the last backup, to decide
-which files to include in the archive being created. That file will
-then be updated by @command{tar}. If the file @var{file} does not exist
-when this option is specified, @command{tar} will create it, and include
-all appropriate files in the archive.
-
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @command{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.
+@smallexample
+$ @kbd{cp /var/log/usr.snar /var/log/usr.snar-1}
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar-1 \
+ /usr}
+@end smallexample
Incremental dumps depend crucially on time stamps, so the results are
-unreliable if you modify a file's time stamps during dumping (e.g.@:
-with the @samp{--atime-preserve} option), or if you set the clock
+unreliable if you modify a file's time stamps during dumping (e.g.,
+with the @option{--atime-preserve=replace} option), or if you set the clock
backwards.
-Despite it should be obvious that a device has a non-volatile value, NFS
-devices have non-dependable values when an automounter gets in the picture.
-This led to a great deal of spurious redumping in incremental dumps,
-so it is somewhat useless to compare two NFS devices numbers over time.
-So @command{tar} now considers all NFS devices as being equal when it comes
-to comparing directories; this is fairly gross, but there does not seem
+Metadata stored in snapshot files include device numbers, which,
+obviously is supposed to be a non-volatile value. However, it turns
+out that NFS devices have undependable values when an automounter
+gets in the picture. This can lead to a great deal of spurious
+redumping in incremental dumps, so it is somewhat useless to compare
+two NFS devices numbers over time. The solution implemented currently
+is to considers all NFS devices as being equal when it comes to
+comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
-@command{tar} doesn't access @var{snapshot-file} when
-@value{op-create} or @value{op-list} are specified, but the
-@value{op-listed-incremental} option must still be given. A
-placeholder @var{snapshot-file} can be specified, e.g.,
-@file{/dev/null}.
+Note that incremental archives use @command{tar} extensions and may
+not be readable by non-@acronym{GNU} versions of the @command{tar} program.
+
+To extract from the incremental dumps, use
+@option{--listed-incremental} together with @option{--extract}
+option (@pxref{extracting files}). In this case, @command{tar} does
+not need to access snapshot file, since all the data necessary for
+extraction are stored in the archive itself. So, when extracting, you
+can give whatever argument to @option{--listed-incremental}, the usual
+practice is to use @option{--listed-incremental=/dev/null}.
+Alternatively, you can use @option{--incremental}, which needs no
+arguments. In general, @option{--incremental} (@option{-G}) can be
+used as a shortcut for @option{--listed-incremental} when listing or
+extracting incremental backups (for more information, regarding this
+option, @pxref{incremental-op}).
+
+When extracting from the incremental backup @GNUTAR{} attempts to
+restore the exact state the file system had when the archive was
+created. In particular, it will @emph{delete} those files in the file
+system that did not exist in their directories when the archive was
+created. If you have created several levels of incremental files,
+then in order to restore the exact contents the file system had when
+the last level was created, you will need to restore from all backups
+in turn. Continuing our example, to restore the state of @file{/usr}
+file system, one would do@footnote{Notice, that since both archives
+were created withouth @option{-P} option (@pxref{absolute}), these
+commands should be run from the root file system.}:
+
+@smallexample
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.1.tar}
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.2.tar}
+@end smallexample
+
+To list the contents of an incremental archive, use @option{--list}
+(@pxref{list}), as usual. To obtain more information about the
+archive, use @option{--listed-incremental} or @option{--incremental}
+combined with two @option{--verbose} options@footnote{Two
+@option{--verbose} options were selected to avoid breaking usual
+verbose listing output (@option{--list --verbose}) when using in
+scripts.
+
+Versions of @GNUTAR{} up to 1.15.1 used to dump verbatim binary
+contents of the DUMPDIR header (with terminating nulls) when
+@option{--incremental} or @option{--listed-incremental} option was
+given, no matter what the verbosity level. This behavior, and,
+especially, the binary output it produced were considered incovenient
+and were changed in version 1.16}:
+
+@smallexample
+@kbd{tar --list --incremental --verbose --verbose archive.tar}
+@end smallexample
+
+This command will print, for each directory in the archive, the list
+of files in that directory at the time the archive was created. This
+information is put out in a format which is both human-readable and
+unambiguous for a program: each file name is printed as
+
+@smallexample
+@var{x} @var{file}
+@end smallexample
-@FIXME{this section needs to be written}
+@noindent
+where @var{x} is a letter describing the status of the file: @samp{Y}
+if the file is present in the archive, @samp{N} if the file is not
+included in the archive, or a @samp{D} if the file is a directory (and
+is included in the archive).@FIXME-xref{dumpdir format}. Each such
+line is terminated by a newline character. The last line is followed
+by an additional newline to indicate the end of the data.
+
+@anchor{incremental-op}The option @option{--incremental} (@option{-G})
+gives the same behavior as @option{--listed-incremental} when used
+with @option{--list} and @option{--extract} options. When used with
+@option{--create} option, it creates an incremental archive without
+creating snapshot file. Thus, it is impossible to create several
+levels of incremental backups with @option{--incremental} option.
@node Backup Levels
@section Levels of Backups
-@UNREVISED
An archive containing all the files in the file system is called a
@dfn{full backup} or @dfn{full dump}. You could insure your data by
are daily re-archived.
It is more efficient to do a full dump only occasionally. To back up
-files between full dumps, you can a incremental dump. A @dfn{level
+files between full dumps, you can use @dfn{incremental dumps}. A @dfn{level
one} dump archives all the files that have changed since the last full
dump.
more than once a day is usually not worth the trouble).
@GNUTAR{} comes with scripts you can use to do full
-and level-one dumps. Using scripts (shell programs) to perform
-backups and restoration is a convenient and reliable alternative to
-typing out file name lists and @command{tar} commands by hand.
+and level-one (actually, even level-two and so on) dumps. Using
+scripts (shell programs) to perform backups and restoration is a
+convenient and reliable alternative to typing out file name lists
+and @command{tar} commands by hand.
Before you use these scripts, you need to edit the file
@file{backup-specs}, which specifies parameters used by the backup
-scripts and by the restore script. @FIXME{There is no such restore
-script!}@FIXME-xref{Script Syntax}Once the backup parameters
-are set, you can perform backups or restoration by running the
-appropriate script.
-
-The name of the restore script is @code{restore}. @FIXME{There is
-no such restore script!}The names of the level one and full backup
-scripts are, respectively, @code{level-1} and @code{level-0}.
-The @code{level-0} script also exists under the name @code{weekly}, and
-the @code{level-1} under the name @code{daily}---these additional names
-can be changed according to your backup schedule. @FIXME-xref{Scripted
-Restoration, for more information on running the restoration script.}
-@FIXME-xref{Scripted Backups, for more information on running the
-backup scripts.}
-
-@emph{Please Note:} The backup scripts and the restoration scripts are
+scripts and by the restore script. This file is usually located
+in @file{/etc/backup} directory. @FIXME-xref{Script Syntax} Once the
+backup parameters are set, you can perform backups or restoration by
+running the appropriate script.
+
+The name of the backup script is @code{backup}. The name of the
+restore script is @code{restore}. The following sections describe
+their use in detail.
+
+@emph{Please Note:} The backup and restoration scripts are
designed to be used together. While it is possible to restore files by
hand from an archive which was created using a backup script, and to create
an archive by hand which could then be extracted using the restore script,
-it is easier to use the scripts.@FIXME{There is no such restore script!}
-@value{xref-incremental}, and @value{xref-listed-incremental},
-before making such an attempt.
-
-@FIXME{shorten node names}
+it is easier to use the scripts. @value{xref-incremental}, before
+making such an attempt.
@node Backup Parameters
@section Setting Parameters for Backups and Restoration
-@UNREVISED
The file @file{backup-specs} specifies backup parameters for the
backup and restoration scripts provided with @command{tar}. You must
edit @file{backup-specs} to fit your system configuration and schedule
before using these scripts.
-@FIXME{This about backup scripts needs to be written: BS is a shell
-script .... thus ... @file{backup-specs} is in shell script syntax.}
+Syntactically, @file{backup-specs} is a shell script, containing
+mainly variable assignments. However, any valid shell construct
+is allowed in this file. Particularly, you may wish to define
+functions within that script (e.g., see @code{RESTORE_BEGIN} below).
+For more information about shell script syntax, please refer to
+@url{http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#ta
+g_02, the definition of the Shell Command Language}. See also
+@ref{Top,,Bash Features,bashref,Bash Reference Manual}.
+
+The shell variables controlling behavior of @code{backup} and
+@code{restore} are described in the following subsections.
-@FIXME-xref{Script Syntax, for an explanation of this syntax.}
+@menu
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
+* backup-specs example:: An Example Text of @file{Backup-specs}
+@end menu
-@FIXME{Whats a parameter .... looked at by the backup scripts
-... which will be expecting to find ... now syntax ... value is linked
-to lame ... @file{backup-specs} specifies the following parameters:}
+@node General-Purpose Variables
+@subsection General-Purpose Variables
-@table @samp
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@defvr {Backup variable} ADMINISTRATOR
+The user name of the backup administrator. @code{Backup} scripts
+sends a backup report to this address.
+@end defvr
-@item BACKUP_HOUR
+@defvr {Backup variable} BACKUP_HOUR
The hour at which the backups are done. This can be a number from 0
-to 23, or the string @samp{now}.
+to 23, or the time specification in form @var{hours}:@var{minutes},
+or the string @samp{now}.
-@item TAPE_FILE
-The device @command{tar} writes the archive to. This device should be
-attached to the host on which the dump scripts are run.
+This variable is used by @code{backup}. Its value may be overridden
+using @option{--time} option (@pxref{Scripted Backups}).
+@end defvr
-@FIXME{examples for all ...}
+@defvr {Backup variable} TAPE_FILE
-@item TAPE_STATUS
-The command to use to obtain the status of the archive device,
-including error count. On some tape drives there may not be such a
-command; in that case, simply use @samp{TAPE_STATUS=false}.
+The device @command{tar} writes the archive to. If @var{TAPE_FILE}
+is a remote archive (@pxref{remote-dev}), backup script will suppose
+that your @command{mt} is able to access remote devices. If @var{RSH}
+(@pxref{RSH}) is set, @option{--rsh-command} option will be added to
+invocations of @command{mt}.
+@end defvr
+
+@defvr {Backup variable} BLOCKING
-@item BLOCKING
The blocking factor @command{tar} will use when writing the dump archive.
@value{xref-blocking-factor}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_DIRS
-@item BACKUP_DIRS
-A list of file systems to be dumped. You can include any directory
-name in the list---subdirectories on that file system will be
+A list of file systems to be dumped (for @code{backup}), or restored
+(for @code{restore}). You can include any directory
+name in the list --- subdirectories on that file system will be
included, regardless of how they may look to other networked machines.
Subdirectories on other file systems will be ignored.
the host machine must have @GNUTAR{} installed, and
must be able to access the directory containing the backup scripts and
their support files using the same file name that is used on the
-machine where the scripts are run (ie. what @command{pwd} will print
+machine where the scripts are run (ie. what @command{pwd} will print
when in that directory on that machine). If the host that contains
the file system does not have this capability, you can specify another
host as long as it can access the file system through NFS.
-@item BACKUP_FILES
-A list of individual files to be dumped. These should be accessible
-from the machine on which the backup script is run.
+If the list of file systems is very long you may wish to put it
+in a separate file. This file is usually named
+@file{/etc/backup/dirs}, but this name may be overridden in
+@file{backup-specs} using @code{DIRLIST} variable.
+@end defvr
-@FIXME{Same file name, be specific. Through NFS ...}
+@defvr {Backup variable} DIRLIST
-@end table
+A path to the file containing the list of the file systems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
+@end defvr
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+@defvr {Backup variable} BACKUP_FILES
-@node backup-specs example
-@subsection An Example Text of @file{Backup-specs}
-@UNREVISED
+A list of individual files to be dumped (for @code{backup}), or restored
+(for @code{restore}). These should be accessible from the machine on
+which the backup script is run.
-The following is the text of @file{backup-specs} as it appears at FSF:
+If the list of file systems is very long you may wish to store it
+in a separate file. This file is usually named
+@file{/etc/backup/files}, but this name may be overridden in
+@file{backup-specs} using @code{FILELIST} variable.
+@end defvr
-@smallexample
-# site-specific parameters for file system backup.
+@defvr {Backup variable} FILELIST
-ADMINISTRATOR=friedman
-BACKUP_HOUR=1
-TAPE_FILE=/dev/nrsmt0
-TAPE_STATUS="mts -t $TAPE_FILE"
-BLOCKING=124
-BACKUP_DIRS="
- albert:/fs/fsf
- apple-gunkies:/gd
- albert:/fs/gd2
- albert:/fs/gp
- geech:/usr/jla
- churchy:/usr/roland
- albert:/
- albert:/usr
- apple-gunkies:/
- apple-gunkies:/usr
- gnu:/hack
- gnu:/u
- apple-gunkies:/com/mailer/gnu
- apple-gunkies:/com/archive/gnu"
+A path to the file containing the list of the individual files to backup
+or restore. By default it is @file{/etc/backup/files}.
+@end defvr
-BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
+@defvr {Backup variable} MT
-@end smallexample
+Full file name of @command{mt} binary.
+@end defvr
-@node Script Syntax
-@subsection Syntax for @file{Backup-specs}
-@UNREVISED
+@defvr {Backup variable} RSH
+@anchor{RSH}
+Full file name of @command{rsh} binary or its equivalent. You may wish to
+set it to @code{ssh}, to improve security. In this case you will have
+to use public key authentication.
+@end defvr
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@FIXME{"conventions?"}
+@defvr {Backup variable} RSH_COMMAND
-A quoted string is considered to be contiguous, even if it is on more
-than one line. Therefore, you cannot include commented-out lines
-within a multi-line quoted string. BACKUP_FILES and BACKUP_DIRS are
-the two most likely parameters to be multi-line.
+Full file name of @command{rsh} binary on remote mashines. This will
+be passed via @option{--rsh-command} option to the remote invocation
+of @GNUTAR{}.
+@end defvr
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
+@defvr {Backup variable} VOLNO_FILE
-@node Scripted Backups
+Name of temporary file to hold volume numbers. This needs to be accessible
+by all the machines which have file systems to be dumped.
+@end defvr
+
+@defvr {Backup variable} XLIST
+
+Name of @dfn{exclude file list}. An @dfn{exclude file list} is a file
+located on the remote machine and containing the list of files to
+be excluded from the backup. Exclude file lists are searched in
+/etc/tar-backup directory. A common use for exclude file lists
+is to exclude files containing security-sensitive information
+(e.g., @file{/etc/shadow} from backups).
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} SLEEP_TIME
+
+Time to sleep between dumps of any two successive file systems
+
+This variable affects only @code{backup}.
+@end defvr
+
+@defvr {Backup variable} DUMP_REMIND_SCRIPT
+
+Script to be run when it's time to insert a new tape in for the next
+volume. Administrators may want to tailor this script for their site.
+If this variable isn't set, @GNUTAR{} will display its built-in prompt
+@FIXME-xref{describe it somewhere!}, and will expect confirmation from
+the console.
+@end defvr
+
+@defvr {Backup variable} SLEEP_MESSAGE
+
+Message to display on the terminal while waiting for dump time. Usually
+this will just be some literal text.
+@end defvr
+
+@defvr {Backup variable} TAR
+
+Full file name of the @GNUTAR{} executable. If this is not set, backup
+scripts will search @command{tar} in the current shell path.
+@end defvr
+
+@node Magnetic Tape Control
+@subsection Magnetic Tape Control
+
+Backup scripts access tape device using special @dfn{hook functions}.
+These functions take a single argument -- the name of the tape
+device. Their names are kept in the following variables:
+
+@defvr {Backup variable} MT_BEGIN
+The name of @dfn{begin} function. This function is called before
+accessing the drive. By default it retensions the tape:
+
+@smallexample
+MT_BEGIN=mt_begin
+
+mt_begin() @{
+ mt -f "$1" retension
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_REWIND
+The name of @dfn{rewind} function. The default definition is as
+follows:
+
+@smallexample
+MT_REWIND=mt_rewind
+
+mt_rewind() @{
+ mt -f "$1" rewind
+@}
+@end smallexample
+
+@end defvr
+
+@defvr {Backup variable} MT_OFFLINE
+The name of the function switching the tape off line. By default
+it is defined as follows:
+
+@smallexample
+MT_OFFLINE=mt_offline
+
+mt_offline() @{
+ mt -f "$1" offl
+@}
+@end smallexample
+@end defvr
+
+@defvr {Backup variable} MT_STATUS
+The name of the function used to obtain the status of the archive device,
+including error count. Default definition:
+
+@smallexample
+MT_STATUS=mt_status
+
+mt_status() @{
+ mt -f "$1" status
+@}
+@end smallexample
+@end defvr
+
+@node User Hooks
+@subsection User Hooks
+
+@dfn{User hooks} are shell functions executed before and after
+each @command{tar} invocation. Thus, there are @dfn{backup
+hooks}, which are executed before and after dumping each file
+system, and @dfn{restore hooks}, executed before and
+after restoring a file system. Each user hook is a shell function
+taking four arguments:
+
+@deffn {User Hook Function} hook @var{level} @var{host} @var{fs} @var{fsname}
+Its arguments are:
+
+@table @var
+@item level
+Current backup or restore level.
+
+@item host
+Name or IP address of the host machine being dumped or restored.
+
+@item fs
+Full path name to the file system being dumped or restored.
+
+@item fsname
+File system name with directory separators replaced with colons. This
+is useful, e.g., for creating unique files.
+@end table
+@end deffn
+
+Following variables keep the names of user hook functions
+
+@defvr {Backup variable} DUMP_BEGIN
+Dump begin function. It is executed before dumping the file system.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the file system.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the file system.
+@end defvr
+
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the file system.
+@end defvr
+
+@node backup-specs example
+@subsection An Example Text of @file{Backup-specs}
+
+The following is an example of @file{backup-specs}:
+
+@smallexample
+# site-specific parameters for file system backup.
+
+ADMINISTRATOR=friedman
+BACKUP_HOUR=1
+TAPE_FILE=/dev/nrsmt0
+
+# Use @code{ssh} instead of the less secure @code{rsh}
+RSH=/usr/bin/ssh
+RSH_COMMAND=/usr/bin/ssh
+
+# Override MT_STATUS function:
+my_status() @{
+ mts -t $TAPE_FILE
+@}
+MT_STATUS=my_status
+
+# Disable MT_OFFLINE function
+MT_OFFLINE=:
+
+BLOCKING=124
+BACKUP_DIRS="
+ albert:/fs/fsf
+ apple-gunkies:/gd
+ albert:/fs/gd2
+ albert:/fs/gp
+ geech:/usr/jla
+ churchy:/usr/roland
+ albert:/
+ albert:/usr
+ apple-gunkies:/
+ apple-gunkies:/usr
+ gnu:/hack
+ gnu:/u
+ apple-gunkies:/com/mailer/gnu
+ apple-gunkies:/com/archive/gnu"
+
+BACKUP_FILES="/com/mailer/aliases /com/mailer/league*[a-z]"
+
+@end smallexample
+
+@node Scripted Backups
@section Using the Backup Scripts
-@UNREVISED
The syntax for running a backup script is:
@smallexample
-@file{script-name} [@var{time-to-be-run}]
+backup --level=@var{level} --time=@var{time}
@end smallexample
-where @var{time-to-be-run} can be a specific system time, or can be
-@kbd{now}. If you do not specify a time, the script runs at the time
-specified in @file{backup-specs}. @FIXME-pxref{Script Syntax}
+The @option{level} option requests the dump level. Thus, to produce
+a full dump, specify @code{--level=0} (this is the default, so
+@option{--level} may be omitted if its value is @code{0}).
+@footnote{For backward compatibility, the @code{backup} will also
+try to deduce the requested dump level from the name of the
+script itself. If the name consists of a string @samp{level-}
+followed by a single decimal digit, that digit is taken as
+the dump level number. Thus, you may create a link from @code{backup}
+to @code{level-1} and then run @code{level-1} whenever you need to
+create a level one dump.}
+
+The @option{--time} option determines when should the backup be
+run. @var{Time} may take three forms:
+
+@table @asis
+@item @var{hh}:@var{mm}
+
+The dump must be run at @var{hh} hours @var{mm} minutes.
+
+@item @var{hh}
+
+The dump must be run at @var{hh} hours
+
+@item now
+
+The dump must be run immediately.
+@end table
You should start a script with a tape or disk mounted. Once you
start a script, it prompts you for new tapes or disks as it
needs them. Media volumes don't have to correspond to archive
-files---a multi-volume archive can be started in the middle of a
+files --- a multi-volume archive can be started in the middle of a
tape that already contains the end of another multi-volume archive.
The @code{restore} script prompts for media by its archive volume,
so to avoid an error message you should keep track of which tape
-(or disk) contains which volume of the archive. @FIXME{There is
-no such restore script!} @FIXME-xref{Scripted Restoration}
-@FIXME{Have file names changed?}
+(or disk) contains which volume of the archive (@pxref{Scripted
+Restoration}).
The backup scripts write two files on the file system. The first is a
record file in @file{/etc/tar-backup/}, which is used by the scripts
messages that were generated, as well as how much space was left in
the media volume after the last volume of the archive was written.
You should check this log file after every backup. The file name is
-@file{log-@var{mmm-ddd-yyyy}-level-1} or
-@file{log-@var{mmm-ddd-yyyy}-full}.
+@file{log-@var{mm-dd-yyyy}-level-@var{n}}, where @var{mm-dd-yyyy}
+represents current date, and @var{n} represents current dump level number.
The script also prints the name of each system being dumped to the
standard output.
+Following is the full list of options accepted by @code{backup}
+script:
+
+@table @option
+@item -l @var{level}
+@itemx --level=@var{level}
+Do backup level @var{level} (default 0).
+
+@item -f
+@itemx --force
+Force backup even if today's log file already exists.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -t @var{start-time}
+@itemx --time=@var{start-time}
+Wait till @var{time}, then do backup.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@end table
+
+
@node Scripted Restoration
@section Using the Restore Script
-@UNREVISED
-@ifset PUBLISH
+To restore files that were archived using a scripted backup, use the
+@code{restore} script. Its usage is quite straightforward. In the
+simplest form, invoke @code{restore --all}, it will
+then restore all the file systems and files specified in
+@file{backup-specs} (@pxref{General-Purpose Variables,BACKUP_DIRS}).
-The @command{tar} distribution does not provide restoring scripts.
+You may select the file systems (and/or files) to restore by
+giving @code{restore} list of @dfn{patterns} in its command
+line. For example, running
-@end ifset
+@smallexample
+restore 'albert:*'
+@end smallexample
-@ifclear PUBLISH
+@noindent
+will restore all file systems on the machine @samp{albert}. A more
+complicated example:
-@quotation
-@strong{Warning:} The @GNUTAR{} distribution does @emph{not}
-provide any such @code{restore} script yet. This section is only
-listed here for documentation maintenance purposes. In any case,
-all contents is subject to change as things develop.
-@end quotation
+@smallexample
+restore 'albert:*' '*:/var'
+@end smallexample
-@FIXME{A section on non-scripted restore may be a good idea.}
+@noindent
+This command will restore all file systems on the machine @samp{albert}
+as well as @file{/var} file system on all machines.
-To restore files that were archived using a scripted backup, use the
-@code{restore} script. The syntax for the script is:
+By default @code{restore} will start restoring files from the lowest
+available dump level (usually zero) and will continue through
+all available dump levels. There may be situations where such a
+thorough restore is not necessary. For example, you may wish to
+restore only files from the recent level one backup. To do so,
+use @option{--level} option, as shown in the example below:
+
+@smallexample
+restore --level=1
+@end smallexample
-where ***** are the file systems to restore from, and
-***** is a regular expression which specifies which files to
-restore. If you specify --all, the script restores all the files
-in the file system.
+The full list of options accepted by @code{restore} follows:
+
+@table @option
+@item -a
+@itemx --all
+Restore all file systems and files specified in @file{backup-specs}
+
+@item -l @var{level}
+@itemx --level=@var{level}
+Start restoring from the given backup level, instead of the default 0.
+
+@item -v[@var{level}]
+@itemx --verbose[=@var{level}]
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
+is 100, which means the highest debugging level.
+
+@item -h
+@itemx --help
+Display short help message and exit.
+
+@item -L
+@itemx --license
+Display program license and exit.
+
+@item -V
+@itemx --version
+Display program version and exit.
+@end table
You should start the restore script with the media containing the
first volume of the archive mounted. The script will prompt for other
the tape as needed. @FIXME-xref{Media, for a discussion of tape
positioning.}
-If you specify @samp{--all} as the @var{files} argument, the
-@code{restore} script extracts all the files in the archived file
-system into the active file system.
-
@quotation
@strong{Warning:} The script will delete files from the active file
system if they were not in the file system when the archive was made.
@end quotation
-@value{xref-incremental}, and @value{ref-listed-incremental},
-for an explanation of how the script makes that determination.
-
-@FIXME{this may be an option, not a given}
-
-@end ifclear
+@value{xref-incremental}, for an explanation of how the script makes
+that determination.
@node Choosing
@chapter Choosing Files and Names for @command{tar}
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
@end menu
@node file
option allows you to either specify or name a file to use as the archive
instead of the default archive file location.
-@table @kbd
+@table @option
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Name the archive to create or operate on. Use in conjunction with
@noindent
@file{collection.tar} is the name of the archive. It must directly
-follow the @samp{-f} option, since whatever directly follows @samp{-f}
+follow the @option{-f} option, since whatever directly follows @option{-f}
@emph{will} end up naming the archive. If you neglect to specify an
archive name, you may end up overwriting a file in the working directory
with the archive you create since @command{tar} will use this file's name
If you do not name the archive, @command{tar} uses the value of the
environment variable @env{TAPE} as the file name for the archive. If
that is not available, @command{tar} uses a default, compiled-in archive
-name, usually that for tape unit zero (ie. @file{/dev/tu00}).
+name, usually that for tape unit zero (ie. @file{/dev/tu00}).
@command{tar} always needs an archive name.
If you use @file{-} as an @var{archive-name}, @command{tar} reads the
"notable tar usages".}
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
@end smallexample
@FIXME{help!}
@cindex Standard input and output
@cindex tar to standard input and output
+@anchor{remote-dev}
To specify an archive file on a device attached to a remote machine,
use the following:
@noindent
@command{tar} will complete the remote connection, if possible, and
prompt you for a username and password. If you use
-@samp{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
+@option{--file=@@@var{hostname}:/@var{dev}/@var{file name}}, @command{tar}
will complete the remote connection, if possible, using your username
as the username on the remote machine.
(along with the @samp{@@} sign), then your user name will be used.
(This is the normal @command{rsh} behavior.) It is necessary for the
remote machine, in addition to permitting your @command{rsh} access, to
-have the @file{/usr/ucb/rmt} program installed. If you need to use a
-file whose name includes a colon, then the remote tape drive behavior
+have the @file{rmt} program installed (This command is included in
+the @GNUTAR{} distribution and by default is installed under
+@file{@var{prefix}/libexec/rmt}, were @var{prefix} means your
+installation prefix). If you need to use a file whose name includes a
+colon, then the remote tape drive behavior
can be inhibited by using the @value{op-force-local} option.
@FIXME{i know we went over this yesterday, but bob (and now i do again,
@kbd{tar} @var{operation} [@var{option1} @var{option2} @dots{}] [@var{file name-1} @var{file name-2} @dots{}]
@end smallexample
+If a file name begins with dash (@samp{-}), preceede it with
+@option{--add-file} option to preventit from being treated as an
+option.
+
If you specify a directory name as a file name argument, all the files
in that directory are operated on by @command{tar}.
@node files
@section Reading Names from a File
-@UNREVISED
@cindex Reading file names from a file
@cindex Lists of file names
line, you can put the names into a file, and then use the
@value{op-files-from} option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
-@samp{--files-from}. In the list, the file names should be separated by
+@option{--files-from}. In the list, the file names should be separated by
newlines. You will frequently use this option when you have generated
the list of files to archive with the @command{find} utility.
-@table @kbd
+@table @option
@item --files-from=@var{file name}
@itemx -T @var{file name}
Get names to extract or create from file @var{file name}.
@end table
-If you give a single dash as a file name for @samp{--files-from}, (i.e.,
-you specify either @samp{--files-from=-} or @samp{-T -}), then the file
+If you give a single dash as a file name for @option{--files-from}, (i.e.,
+you specify either @code{--files-from=-} or @code{-T -}), then the file
names are read from standard input.
-Unless you are running @command{tar} with @samp{--create}, you can not use
-both @samp{--files-from=-} and @samp{--file=-} (@samp{-f -}) in the same
+Unless you are running @command{tar} with @option{--create}, you can not use
+both @code{--files-from=-} and @code{--file=-} (@code{-f -}) in the same
command.
+Any number of @option{-T} options can be given in the command line.
+
@FIXME{add bob's example, from his message on 2-10-97}
The following example shows how to use @command{find} to generate a list of
files smaller than 400K in length and put that list into a file
-called @file{small-files}. You can then use the @samp{-T} option to
+called @file{small-files}. You can then use the @option{-T} option to
@command{tar} to specify the files from that file, @file{small-files}, to
-create the archive @file{little.tgz}. (The @samp{-z} option to
+create the archive @file{little.tgz}. (The @option{-z} option to
@command{tar} compresses the archive with @command{gzip}; @pxref{gzip} for
more information.)
@smallexample
-$ @kbd{find . -size -400 -print > small-files}
+$ @kbd{find . -size -400 -print > small-files}
$ @kbd{tar -c -v -z -T small-files -f little.tgz}
@end smallexample
@noindent
-@FIXME{say more here to conclude the example/section?}
+In the file list given by @option{-T} option, any file name beginning
+with @samp{-} character is considered a @command{tar} option and is
+processed accordingly.@footnote{Versions of @GNUTAR{} up to 1.15.1
+recognized only @option{-C} option in file lists, and only if the
+option and its argument occupied two consecutive lines.} For example,
+the common use of this feature is to change to another directory by
+specifying @option{-C} option:
+
+@smallexample
+@group
+$ @kbd{cat list}
+-C/etc
+passwd
+hosts
+-C/lib
+libc.a
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end group
+@end smallexample
+
+@noindent
+In this example, @command{tar} will first switch to @file{/etc}
+directory and add files @file{passwd} and @file{hosts} to the
+archive. Then it will change to @file{/lib} directory and will archive
+the file @file{libc.a}. Thus, the resulting archive @file{foo.tar} will
+contain:
+
+@smallexample
+@group
+$ @kbd{tar tf foo.tar}
+passwd
+hosts
+libc.a
+@end group
+@end smallexample
+
+@noindent
+Notice that the option parsing algorithm used with @option{-T} is
+stricter than the one used by shell. Namely, when specifying option
+arguments, you should observe the following rules:
+
+@itemize @bullet
+@item
+When using short (single-letter) option form, its argument must
+immediately follow the option letter, without any intervening
+whitespace. For example: @code{-Cdir}.
+
+@item
+When using long option form, the option argument must be separated
+from the option by a single equal sign. No whitespace is allowed on
+any side of the equal sign. For example: @code{--directory=dir}.
+
+@item
+For both short and long option forms, the option argument can be given
+on the next line after the option name, e.g.:
+
+@smallexample
+@group
+--directory
+dir
+@end group
+@end smallexample
+
+@noindent
+and
+
+@smallexample
+@group
+-C
+dir
+@end group
+@end smallexample
+@end itemize
+
+@cindex @option{--add-file}
+If you happen to have a file whose name starts with @samp{-},
+precede it with @option{--add-file} option to prevent it from
+being recognized as an option. For example: @code{--add-file --my-file}.
@menu
* nul::
@end menu
@node nul
-@subsection @kbd{NUL} Terminated File Names
+@subsection @code{NUL} Terminated File Names
-@cindex File names, terminated by @kbd{NUL}
-@cindex @kbd{NUL} terminated file names
+@cindex File names, terminated by @code{NUL}
+@cindex @code{NUL} terminated file names
The @value{op-null} option causes @value{op-files-from} to read file
names terminated by a @code{NUL} instead of a newline, so files whose
-names contain newlines can be archived using @samp{--files-from}.
+names contain newlines can be archived using @option{--files-from}.
-@table @kbd
+@table @option
@item --null
-Only consider @kbd{NUL} terminated file names, instead of files that
+Only consider @code{NUL} terminated file names, instead of files that
terminate in a newline.
@end table
-The @samp{--null} option is just like the one in @acronym{GNU}
+The @value{op-null} option is just like the one in @acronym{GNU}
@command{xargs} and @command{cpio}, and is useful with the
-@samp{-print0} predicate of @acronym{GNU} @command{find}. In
-@command{tar}, @samp{--null} also causes @value{op-directory} options
-to be treated as file names to archive, in case there are any files
-out there called @file{-C}.
+@option{-print0} predicate of @acronym{GNU} @command{find}. In
+@command{tar}, @value{op-null} also disables special handling for
+file names that begin with dash.
This example shows how to use @command{find} to generate a list of files
larger than 800K in length and put that list into a file called
-@file{long-files}. The @samp{-print0} option to @command{find} just just
-like @samp{-print}, except that it separates files with a @kbd{NUL}
+@file{long-files}. The @option{-print0} option to @command{find} is just
+like @option{-print}, except that it separates files with a @code{NUL}
rather than with a newline. You can then run @command{tar} with both the
-@samp{--null} and @samp{-T} options to specify that @command{tar} get the
+@option{--null} and @option{-T} options to specify that @command{tar} get the
files from that file, @file{long-files}, to create the archive
-@file{big.tgz}. The @samp{--null} option to @command{tar} will cause
-@command{tar} to recognize the @kbd{NUL} separator between files.
+@file{big.tgz}. The @option{--null} option to @command{tar} will cause
+@command{tar} to recognize the @code{NUL} separator between files.
@smallexample
-$ @kbd{find . -size +800 -print0 > long-files}
+$ @kbd{find . -size +800 -print0 > long-files}
$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
@end smallexample
To avoid operating on files whose names match a particular pattern,
use the @value{op-exclude} or @value{op-exclude-from} options.
-@table @kbd
+@table @option
@item --exclude=@var{pattern}
Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
@file{src} except for files whose names end in @file{.o}, use the
command @samp{tar -cf src.tar --exclude='*.o' src}.
-You may give multiple @samp{--exclude} options.
+You may give multiple @option{--exclude} options.
-@table @kbd
+@table @option
@item --exclude-from=@var{file}
@itemx -X @var{file}
Causes @command{tar} to ignore files that match the patterns listed in
@end table
@findex exclude-from
-Use the @samp{--exclude-from=@var{file-of-patterns}} option to read a
+Use the @option{--exclude-from=@var{file-of-patterns}} option to read a
list of patterns, one per line, from @var{file}; @command{tar} will
ignore files matching those patterns. Thus if @command{tar} is
called as @w{@samp{tar -c -X foo .}} and the file @file{foo} contains a
@FIXME{do the exclude options files need to have stuff separated by
newlines the same as the files-from option does?}
+@table @option
+@item --exclude-caches
+Causes @command{tar} to ignore directories containing a cache directory tag.
+@end table
+
+@findex exclude-caches
+When creating an archive,
+the @option{--exclude-caches} option
+causes @command{tar} to exclude all directories
+that contain a @dfn{cache directory tag}.
+A cache directory tag is a short file
+with the well-known name @file{CACHEDIR.TAG}
+and having a standard header
+specified in @url{http://www.brynosaurus.com/cachedir/spec.html}.
+Various applications write cache directory tags
+into directories they use to hold regenerable, non-precious data,
+so that such data can be more easily excluded from backups.
+
@menu
* controlling pattern-patching with exclude::
* problems with exclude::
@table @option
@item --anchored
@itemx --no-anchored
-If anchored (the default), a pattern must match an initial subsequence
-of the name's components. Otherwise, the pattern can match any subsequence.
+If anchored, a pattern must match an initial subsequence
+of the name's components. Otherwise, the pattern can match any
+subsequence. Default is @option{--no-anchored}.
@item --ignore-case
@itemx --no-ignore-case
You can sometimes confuse the meanings of @value{op-exclude} and
@value{op-exclude-from}. Be careful: use @value{op-exclude} when files
to be excluded are given as a pattern on the command line. Use
-@samp{--exclude-from=@var{file-of-patterns}} to introduce the name of a
+@option{--exclude-from=@var{file-of-patterns}} to introduce the name of a
file which contains a list of patterns, one per line; each of these
patterns can exclude zero, one, or many files.
@item
In earlier versions of @command{tar}, what is now the
-@samp{--exclude-from=@var{file-of-patterns}} option was called
-@samp{--exclude=@var{pattern}} instead. Now,
-@samp{--exclude=@var{pattern}} applies to patterns listed on the command
-line and @samp{--exclude-from=@var{file-of-patterns}} applies to
+@option{--exclude-from=@var{file-of-patterns}} option was called
+@option{--exclude=@var{pattern}} instead. Now,
+@option{--exclude=@var{pattern}} applies to patterns listed on the command
+line and @option{--exclude-from=@var{file-of-patterns}} applies to
patterns listed in a file.
@end itemize
@samp{*} or @samp{?} for example, are replaced and expanded into all
existing files matching the given pattern. However, @command{tar} often
uses wildcard patterns for matching (or globbing) archive members instead
-of actual files in the filesystem. Wildcard patterns are also used for
+of actual files in the file system. Wildcard patterns are also used for
verifying volume labels of @command{tar} archives. This section has the
purpose of explaining wildcard syntax for @command{tar}.
@node after
@section Operating Only on New Files
@cindex Excluding file by age
+@cindex Data Modification time, excluding files by
@cindex Modification time, excluding files by
@cindex Age, excluding files by
@UNREVISED
The @value{op-after-date} option causes @command{tar} to only work on files
-whose modification or inode-changed times are newer than the @var{date}
+whose data modification or status change times are newer than the @var{date}
given. If @var{date} starts with @samp{/} or @samp{.}, it is taken to
-be a file name; the last-modified time of that file is used as the date.
+be a file name; the data modification time of that file is used as the date.
If you use this option when creating or appending to an archive,
-the archive will only include new files. If you use @samp{--after-date}
+the archive will only include new files. If you use @option{--after-date}
when extracting an archive, @command{tar} will only extract files newer
than the @var{date} you specify.
If you only want @command{tar} to make the date comparison based on
-modification of the actual contents of the file (rather than inode
+modification of the file's data (rather than status
changes), then use the @value{op-newer-mtime} option.
You may use these options with any operation. Note that these options
specify a particular date against which @command{tar} can compare when
deciding whether or not to archive the files.
-@table @kbd
+@table @option
@item --after-date=@var{date}
@itemx --newer=@var{date}
@itemx -N @var{date}
Only store files newer than @var{date}.
-Acts on files only if their modification or inode-changed times are
+Acts on files only if their data modification or status change times are
later than @var{date}. Use in conjunction with any operation.
If @var{date} starts with @samp{/} or @samp{.}, it is taken to be a file
-name; the last-modified time of that file is used as the date.
+name; the data modification time of that file is used as the date.
@item --newer-mtime=@var{date}
-Acts like @value{op-after-date}, but only looks at modification times.
+Acts like @value{op-after-date}, but only looks at data modification times.
@end table
-These options limit @command{tar} to only operating on files which have
-been modified after the date specified. A file is considered to have
-changed if the contents have been modified, or if the owner,
+These options limit @command{tar} to operate only on files which have
+been modified after the date specified. A file's status is considered to have
+changed if its contents have been modified, or if its owner,
permissions, and so forth, have been changed. (For more information on
how to specify a date, see @ref{Date input formats}; remember that the
entire date argument must be quoted if it contains any spaces.)
-Gurus would say that @value{op-after-date} tests both the @code{mtime}
-(time the contents of the file were last modified) and @code{ctime}
-(time the file's status was last changed: owner, permissions, etc)
-fields, while @value{op-newer-mtime} tests only @code{mtime} field.
+Gurus would say that @value{op-after-date} tests both the data
+modification time (@code{mtime}, the time the contents of the file
+were last modified) and the status change time (@code{ctime}, the time
+the file's status was last changed: owner, permissions, etc.@:)
+fields, while @value{op-newer-mtime} tests only the @code{mtime}
+field.
To be precise, @value{op-after-date} checks @emph{both} @code{mtime} and
@code{ctime} and processes the file if either one is more recent than
@strong{Please Note:} @value{op-after-date} and @value{op-newer-mtime}
should not be used for incremental backups. Some files (such as those
in renamed directories) are not selected properly by these options.
-@xref{incremental and listed-incremental}.
+@xref{Incremental Dumps}.
@end quotation
@noindent
want @command{tar} to act this way.
The @value{op-no-recursion} option inhibits @command{tar}'s recursive descent
-into specified directories. If you specify @samp{--no-recursion}, you can
+into specified directories. If you specify @option{--no-recursion}, you can
use the @command{find} utility for hunting through levels of directories to
construct a list of file names which you could then pass to @command{tar}.
@command{find} allows you to be more selective when choosing which files to
archive; see @ref{files} for more information on using @command{find} with
@command{tar}, or look.
-@table @kbd
+@table @option
@item --no-recursion
Prevents @command{tar} from recursively descending directories.
This is the default.
@end table
-When you use @samp{--no-recursion}, @GNUTAR{} grabs
+When you use @option{--no-recursion}, @GNUTAR{} grabs
directory entries themselves, but does not descend on them
recursively. Many people use @command{find} for locating files they
want to back up, and since @command{tar} @emph{usually} recursively
-descends on directories, they have to use the @samp{@w{! -d}} option
+descends on directories, they have to use the @samp{@w{! -d}} option
to @command{find} @FIXME{needs more explanation or a cite to another
info file}as they usually do not want all the files in a directory.
They then use the @value{op-files-from} option to archive the files
other than @file{grape/concord}.
@node one
-@section Crossing Filesystem Boundaries
+@section Crossing File System Boundaries
@cindex File system boundaries, not crossing
@UNREVISED
@command{tar} will still archive files explicitly named on the command line
or through @value{op-files-from}, regardless of where they reside.
-@table @kbd
+@table @option
@item --one-file-system
@itemx -l
Prevents @command{tar} from crossing file system boundaries when
archiving. Use in conjunction with any write operation.
@end table
-The @samp{--one-file-system} option causes @command{tar} to modify its
+The @option{--one-file-system} option causes @command{tar} to modify its
normal behavior in archiving the contents of directories. If a file in
-a directory is not on the same filesystem as the directory itself, then
+a directory is not on the same file system as the directory itself, then
@command{tar} will not archive that file. If the file is a directory
itself, @command{tar} will not archive anything beneath it; in other words,
@command{tar} will not cross mount points.
working directory to the directory @var{directory} after that point in
the list.
-@table @kbd
+@table @option
@item --directory=@var{directory}
@itemx -C @var{directory}
Changes the working directory in the middle of a command line.
@samp{tar --extract}, the third file will be written in a subdirectory
named @file{orange-colored}.
-You can use the @samp{--directory} option to make the archive
+You can use the @option{--directory} option to make the archive
independent of the original name of the directory holding the files.
The following command places the files @file{/etc/passwd},
@file{/etc/hosts}, and @file{/lib/libc.a} into the archive
They will not appear to be related by file name to the original
directories where those files were located.
-Note that @samp{--directory} options are interpreted consecutively. If
-@samp{--directory} specifies a relative file name, it is interpreted
+Note that @option{--directory} options are interpreted consecutively. If
+@option{--directory} specifies a relative file name, it is interpreted
relative to the then current directory, which might not be the same as
the original current working directory of @command{tar}, due to a previous
-@samp{--directory} option.
+@option{--directory} option.
-@FIXME{dan: does this mean that you *can* use the short option form, but
-you can *not* use the long option form with --files-from? or is this
-totally screwed?}
+When using @option{--files-from} (@pxref{files}), you can put various
+@command{tar} options (including @option{-C}) in the file list. Notice,
+however, that in this case the option and its argument may not be
+separated by whitespace. If you use short option, its argument must
+either follow the option letter immediately, without any intervening
+whitespace, or occupy the next line. Otherwise, if you use long
+option, separate its argument by an equal sign.
-When using @samp{--files-from} (@pxref{files}), you can put @samp{-C}
-options in the file list. Unfortunately, you cannot put
-@samp{--directory} options in the file list. (This interpretation can
-be disabled by using the @value{op-null} option.)
+For instance, the file list for the above example will be:
+
+@smallexample
+@group
+-C
+/etc
+passwd
+hosts
+-C
+/lib
+libc.a
+@end group
+@end smallexample
+
+@noindent
+To use it, you would invoke @command{tar} as follows:
+
+@smallexample
+$ @kbd{tar -c -f foo.tar --files-from list}
+@end smallexample
+
+Notice also that you can only use the short option variant in the file
+list, i.e., always use @option{-C}, not @option{--directory}.
+
+The interpretation of @value{op-directory} is disabled by
+@value{op-null} option.
@node absolute
@subsection Absolute File Names
@UNREVISED
-@table @kbd
+@table @option
@item -P
@itemx --absolute-names
Do not strip leading slashes from file names, and permit file names
leading slashes from member names when putting members into the
archive. For example, if you ask @command{tar} to add the file
@file{/bin/ls} to an archive, it will do so, but the member name will
-be @file{bin/ls}.
+be @file{bin/ls}.@footnote{A side effect of this is that when
+@option{--create} is used with @option{--verbose} the resulting output
+is not, generally speaking, the same as the one you'd get running
+@kbd{tar --list} command. This may be important if you use some
+scripts for comparing both outputs. @xref{listing member and file names},
+for the information on how to handle this case.}
If you use the @value{op-absolute-names} option, @command{tar} will do
none of these transformations.
@FIXME{Is write access an issue?}
-@table @kbd
+@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
archiving files. Preserves leading slash when extracting files.
@table @asis
@item gnu
-Format used by @GNUTAR{}.
+Format used by @GNUTAR{} versions up to 1.13.25. This format derived
+from an early @acronym{POSIX} standard, adding some improvements such as
+sparse file handling and incremental archives. Unfortunately these
+features were implemented in a way incompatible with other archive
+formats.
-@item v7
-Archive format, compatible with the V7 implementation of tar.
+Archives in @samp{gnu} format are able to hold pathnames of unlimited
+length.
@item oldgnu
Format used by @GNUTAR{} of versions prior to 1.12.
-@item posix
-Archive format defined by POSIX.1-2001 specification.
+@item v7
+Archive format, compatible with the V7 implementation of tar. This
+format imposes a number of limitations. The most important of them
+are:
+
+@enumerate
+@item The maximum length of a file name is limited to 99 characters.
+@item The maximum length of a symbolic link is limited to 99 characters.
+@item It is impossible to store special files (block and character
+devices, fifos etc.)
+@item Maximum value of user or group ID is limited to 2097151 (7777777
+octal)
+@item V7 archives do not contain symbolic ownership information (user
+and group name of the file owner).
+@end enumerate
+
+This format has traditionally been used by Automake when producing
+Makefiles. This practice will change in the future, in the meantime,
+however this means that projects containing filenames more than 99
+characters long will not be able to use @GNUTAR{} @value{VERSION} and
+Automake prior to 1.9.
+
+@item ustar
+Archive format defined by @acronym{POSIX.1-1988} specification. It stores
+symbolic ownership information. It is also able to store
+special files. However, it imposes several restrictions as well:
+
+@enumerate
+@item The maximum length of a file name is limited to 256 characters,
+provided that the filename can be split at directory separator in
+two parts, first of them being at most 155 bytes long. So, in most
+cases the maximum file name length will be shorter than 256
+characters.
+@item The maximum length of a symbolic link name is limited to
+100 characters.
+@item Maximum size of a file the archive is able to accomodate
+is 8GB
+@item Maximum value of UID/GID is 2097151.
+@item Maximum number of bits in device major and minor numbers is 21.
+@end enumerate
@item star
-Format used by J@"org Schilling @command{star} implementation.
+Format used by J@"org Schilling @command{star}
+implementation. @GNUTAR{} is able to read @samp{star} archives but
+currently does not produce them.
+
+@item posix
+Archive format defined by @acronym{POSIX.1-2001} specification. This is the
+most flexible and feature-rich format. It does not impose any
+restrictions on file sizes or filename lengths. This format is quite
+recent, so not all tar implementations are able to handle it properly.
+However, this format is designed in such a way that any tar
+implementation able to read @samp{ustar} archives will be able to read
+most @samp{posix} archives as well, with the only exception that any
+additional information (such as long file names etc.) will in such
+case be extracted as plain text files along with the files it refers to.
+
+This archive format will be the default format for future versions
+of @GNUTAR{}.
+
@end table
-@GNUTAR{} is able to create archives in any of these formats,
-except @samp{star}. It is able to read archives in any of these
-formats.
+The following table summarizes the limitations of each of these
+formats:
+
+@multitable @columnfractions .10 .20 .20 .20 .20
+@headitem Format @tab UID @tab File Size @tab Path Name @tab Devn
+@item gnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
+@item oldgnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
+@item v7 @tab 2097151 @tab 8GB @tab 99 @tab n/a
+@item ustar @tab 2097151 @tab 8GB @tab 256 @tab 21
+@item posix @tab Unlimited @tab Unlimited @tab Unlimited @tab Unlimited
+@end multitable
The default format for @GNUTAR{} is defined at compilation
-time. You may check it by running @command{tar --help}, and examining
-the last lines of its output. Usually, @GNUTAR{} is configured
+time. You may check it by running @command{tar --help}, and examining
+the last lines of its output. Usually, @GNUTAR{} is configured
to create archives in @samp{gnu} format, however, future version will
switch to @samp{posix}.
other kind of special files. Do not attempt to save sparse files or
contiguous files as such. Let's discuss a few more problems, in turn.
+@FIXME{Discuss GNU extensions (incremental backups, multi-volume
+archives and archive labels) in GNU and PAX formats.}
+
@menu
* Portable Names:: Portable Names
* dereference:: Symbolic Links
* old:: Old V7 Archives
+* ustar:: Ustar Archives
* gnu:: GNU and old GNU format archives.
-* posix:: @sc{posix} archives
+* posix:: @acronym{POSIX} archives
* Checksumming:: Checksumming Problems
* Large or Negative Values:: Large files, negative time stamps, etc.
@end menu
Normally, when @command{tar} archives a symbolic link, it writes a
block to the archive naming the target of the link. In that way, the
-@command{tar} archive is a faithful record of the filesystem contents.
+@command{tar} archive is a faithful record of the file system contents.
@value{op-dereference} is used with @value{op-create}, and causes
@command{tar} to archive the files symbolic links point to, instead of
the links themselves. When this option is used, when @command{tar}
archive in V7 format (not ANSI), which can be read by these old
versions, specify the @value{op-format-v7} option in
conjunction with the @value{op-create} (@command{tar} also
-accepts @samp{--portability} or @samp{op-old-archive} for this
-option). When you specify it,
+accepts @option{--portability} or @samp{op-old-archive} for this
+option). When you specify it,
@command{tar} leaves out information about directories, pipes, fifos,
contiguous files, and device files, and specifies file ownership by
group and user IDs instead of group and user names.
When updating an archive, do not use @value{op-format-v7}
-unless the archive was created with using this option.
+unless the archive was created using this option.
In most cases, a @emph{new} format archive can be read by an @emph{old}
@command{tar} program without serious trouble, so this option should
able to read old format archives, so it might be safer for you to
always use @value{op-format-v7} for your distributions.
+@node ustar
+@subsection Ustar Archive Format
+
+Archive format defined by @acronym{POSIX}.1-1988 specification is called
+@code{ustar}. Although it is more flexible than the V7 format, it
+still has many restrictions (@xref{Formats,ustar}, for the detailed
+description of @code{ustar} format). Along with V7 format,
+@code{ustar} format is a good choice for archives intended to be read
+with other implementations of @command{tar}.
+
+To create archive in @code{ustar} format, use @value{op-format-ustar}
+option in conjunction with the @value{op-create}.
+
@node gnu
@subsection @acronym{GNU} and old @GNUTAR{} format
@GNUTAR{} was based on an early draft of the
-@sc{posix} 1003.1 @code{ustar} standard. @acronym{GNU} extensions to
+@acronym{POSIX} 1003.1 @code{ustar} standard. @acronym{GNU} extensions to
@command{tar}, such as the support for file names longer than 100
characters, use portions of the @command{tar} header record which were
-specified in that @sc{posix} draft as unused. Subsequent changes in
-@sc{posix} have allocated the same parts of the header record for
+specified in that @acronym{POSIX} draft as unused. Subsequent changes in
+@acronym{POSIX} have allocated the same parts of the header record for
other purposes. As a result, @GNUTAR{} format is
-incompatible with the current @sc{posix} specification, and with
+incompatible with the current @acronym{POSIX} specification, and with
@command{tar} programs that follow it.
In the majority of cases, @command{tar} will be configured to create
-this format by default. This may change in the future, since we plan
-to make @samp{posix} format the default.
+this format by default. This will change in the future releases, since
+we plan to make @samp{posix} format the default.
To force creation a @GNUTAR{} archive, use option
-@value{op-format-gnu}.
-
-Some @command{tar} options are currently basing on @GNUTAR{}
-format, and can therefore be used only with @samp{gnu}
-or @samp{oldgnu} archive formats. The list of such options follows:
-
-@itemize @bullet
-@item @value{op-label}, when used with @value{op-create}.
-@item @value{op-incremental}
-@item @value{op-multi-volume}
-@item @value{op-sparse}
-@end itemize
-
-These options will be re-implemented for the @samp{posix} archive
-format in the future.
+@value{op-format-gnu}.
@node posix
-@subsection @GNUTAR{} and @sc{posix} @command{tar}
+@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
The version @value{VERSION} of @GNUTAR{} is able
-to read and create archives conforming to @sc{posix.1-2001} standard.
+to read and create archives conforming to @acronym{POSIX.1-2001} standard.
-A @sc{posix} conformant archive will be created if @command{tar}
-was given @value{op-format-posix} option, or if it was given
-@value{op-format-gnu} option and the environment variable
-@env{POSIXLY_CORRECT} is set. The later usage is retained for
-compatibility with previous versions of @GNUTAR{}
-and is discouraged.
-
-Notice, that currently @acronym{GNU} extensions are not
-alowed with this format. Following is the list of options that
-cannot be used with @value{op-format-posix}:
-
-@itemize @bullet
-@item @value{op-label}, when used with @value{op-create}.
-@item @value{op-incremental}
-@item @value{op-multi-volume}
-@item @value{op-sparse}
-@end itemize
-
-This restriction will disappear in the future versions.
+A @acronym{POSIX} conformant archive will be created if @command{tar}
+was given @value{op-format-posix} option.
@node Checksumming
@subsection Checksumming Problems
@GNUTAR{} and containing non-ASCII file names, that
is, file names having characters with the eight bit set, because they
use signed checksums, while @GNUTAR{} uses unsigned
-checksums while creating archives, as per @sc{posix} standards. On
+checksums while creating archives, as per @acronym{POSIX} standards. On
reading, @GNUTAR{} computes both checksums and
accept any. It is somewhat worrying that a lot of people may go
around doing backup of their files using faulty (or at least
@cindex future time stamps
@cindex negative time stamps
-@sc{posix} @command{tar} format uses fixed-sized unsigned octal strings
+@acronym{POSIX} @command{tar} format uses fixed-sized unsigned octal strings
to represent numeric values. User and group IDs and device major and
minor numbers have unsigned 21-bit representations, and file sizes and
times have unsigned 33-bit representations. @GNUTAR{}
-generates @sc{posix} representations when possible, but for values
-outside the @sc{posix} range it generates two's-complement base-256
+generates @acronym{POSIX} representations when possible, but for values
+outside the @acronym{POSIX} range it generates two's-complement base-256
strings: uids, gids, and device numbers have signed 57-bit
representations, and file sizes and times have signed 89-bit
-representations. These representations are an extension to @sc{posix}
+representations. These representations are an extension to @acronym{POSIX}
@command{tar} format, so they are not universally portable.
The most common portability problems with out-of-range numeric values
are large files and future or negative time stamps.
-Portable archives should avoid members of 8 GB or larger, as @sc{posix}
+Portable archives should avoid members of 8 GB or larger, as @acronym{POSIX}
@command{tar} format cannot represent them.
-Portable archives should avoid time stamps from the future. @sc{posix}
+Portable archives should avoid time stamps from the future. @acronym{POSIX}
@command{tar} format can represent time stamps in the range 1970-01-01
00:00:00 through 2242-03-16 12:56:31 @sc{utc}. However, many current
hosts use a signed 32-bit @code{time_t}, or internal time stamp format,
portable archives must avoid these time stamps for many years to come.
Portable archives should also avoid time stamps before 1970. These time
-stamps are a common @sc{posix} extension but their @code{time_t}
+stamps are a common @acronym{POSIX} extension but their @code{time_t}
representations are negative. Many traditional @command{tar}
implementations generate a two's complement representation for negative
time stamps that assumes a signed 32-bit @code{time_t}; hence they
@subsection Creating and Reading Compressed Archives
@cindex Compressed archives
@cindex Storing archives in compressed format
-@UNREVISED
-@table @kbd
+@GNUTAR{} is able to create and read compressed archives. It supports
+@command{gzip} and @command{bzip2} compression programs. For backward
+compatibilty, it also supports @command{compress} command, although
+we strongly recommend against using it, since there is a patent
+covering the algorithm it uses and you could be sued for patent
+infringement merely by running @command{compress}! Besides, it is less
+effective than @command{gzip} and @command{bzip2}.
+
+Creating a compressed archive is simple: you just specify a
+@dfn{compression option} along with the usual archive creation
+commands. The compression option is @option{-z} (@option{--gzip}) to
+create a @command{gzip} compressed archive, @option{-j}
+(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
+@option{-Z} (@option{--compress}) to use @command{compress} program.
+For example:
+
+@smallexample
+$ @kbd{tar cfz archive.tar.gz .}
+@end smallexample
+
+Reading compressed archive is even simpler: you don't need to specify
+any additional options as @GNUTAR{} recognizes its format
+automatically. Thus, the following commands will list and extract the
+archive created in previous example:
+
+@smallexample
+# List the compressed archive
+$ @kbd{tar tf archive.tar.gz}
+# Extract the compressed archive
+$ @kbd{tar xf archive.tar.gz}
+@end smallexample
+
+The only case when you have to specify a decompression option while
+reading the archive is when reading from a pipe or from a tape drive
+that does not support random access. However, in this case @GNUTAR{}
+will indicate which option you should use. For example:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tf -}
+tar: Archive is compressed. Use -z option
+tar: Error is not recoverable: exiting now
+@end smallexample
+
+If you see such diagnostics, just add the suggested option to the
+invocation of @GNUTAR{}:
+
+@smallexample
+$ @kbd{cat archive.tar.gz | tar tfz -}
+@end smallexample
+
+Notice also, that there are several restrictions on operations on
+compressed archives. First of all, compressed archives cannot be
+modified, i.e., you cannot update (@value{op-update}) them or delete
+(@value{op-delete}) members from them. Likewise, you cannot append
+another @command{tar} archive to a compressed archive using
+@value{op-append}). Secondly, multi-volume archives cannot be
+compressed.
+
+The following table summarizes compression options used by @GNUTAR{}.
+
+@table @option
@item -z
@itemx --gzip
@itemx --ungzip
Filter the archive through @command{gzip}.
-@end table
-@FIXME{ach; these two bits orig from "compare" (?). where to put?} Some
-format parameters must be taken into consideration when modifying an
-archive.@FIXME{???} Compressed archives cannot be modified.
-
-You can use @samp{--gzip} and @samp{--gunzip} on physical devices
+You can use @option{--gzip} and @option{--gunzip} on physical devices
(tape drives, etc.) and remote files as well as on normal files; data
to or from such devices or remote files is reblocked by another copy
of the @command{tar} program to enforce the specified (or default) record
size. The default compression parameters are used; if you need to
-override them, avoid the @value{op-gzip} option and run @command{gzip}
-explicitly. (Or set the @env{GZIP} environment variable.)
-
-The @value{op-gzip} option does not work with the @value{op-multi-volume}
-option, or with the @value{op-update}, @value{op-append},
-@value{op-concatenate}, or @value{op-delete} operations.
-
-It is not exact to say that @GNUTAR{} is to work in concert
-with @command{gzip} in a way similar to @command{zip}, say. Surely, it is
-possible that @command{tar} and @command{gzip} be done with a single call,
-like in:
+override them, set @env{GZIP} environment variable, e.g.:
@smallexample
-$ @kbd{tar cfz archive.tar.gz subdir}
+$ @kbd{GZIP=--best tar cfz archive.tar.gz subdir}
@end smallexample
@noindent
-to save all of @samp{subdir} into a @code{gzip}'ed archive. Later you
-can do:
+Another way would be to avoid the @value{op-gzip} option and run
+@command{gzip} explicitly:
@smallexample
-$ @kbd{tar xfz archive.tar.gz}
-@end smallexample
-
-@noindent
-to explode and unpack.
-
-The difference is that the whole archive is compressed. With
-@command{zip}, archive members are archived individually. @command{tar}'s
-method yields better compression. On the other hand, one can view the
-contents of a @command{zip} archive without having to decompress it. As
-for the @command{tar} and @command{gzip} tandem, you need to decompress the
-archive to see its contents. However, this may be done without needing
-disk space, by using pipes internally:
-
-@smallexample
-$ @kbd{tar tfz archive.tar.gz}
+$ @kbd{tar cf - subdir | gzip --best -c - > archive.tar.gz}
@end smallexample
@cindex corrupted archives
lose some compressibility. But this would have make recovering easier.
So, there are pros and cons. We'll see!
-@table @kbd
@item -j
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @value{op-gzip}.
Filter the archive through @command{compress}. Otherwise like
@value{op-gzip}.
-@item --use-compress-program=@var{prog}
-Filter through @var{prog} (must accept @samp{-d}).
-@end table
-
-@value{op-compress} stores an archive in compressed format. This
-option is useful in saving time over networks and space in pipes, and
-when storage space is at a premium. @value{op-compress} causes
-@command{tar} to compress when writing the archive, or to uncompress when
-reading the archive.
-
-To perform compression and uncompression on the archive, @command{tar}
-runs the @command{compress} utility. @command{tar} uses the default
-compression parameters; if you need to override them, avoid the
-@value{op-compress} option and run the @command{compress} utility
-explicitly. It is useful to be able to call the @command{compress}
-utility from within @command{tar} because the @command{compress} utility by
-itself cannot access remote tape drives.
-
-The @value{op-compress} option will not work in conjunction with the
-@value{op-multi-volume} option or the @value{op-append}, @value{op-update}
-and @value{op-delete} operations. @xref{Operations}, for
-more information on these operations.
+The @acronym{GNU} Project recommends you not use
+@command{compress}, because there is a patent covering the algorithm it
+uses. You could be sued for patent infringement merely by running
+@command{compress}.
-If there is no compress utility available, @command{tar} will report an error.
-@strong{Please note} that the @command{compress} program may be covered by
-a patent, and therefore we recommend you stop using it.
+@item --use-compress-program=@var{prog}
+Use external compression program @var{prog}. Use this option if you
+have a compression program that @GNUTAR{} does not support. There
+are two requirements to which @var{prog} should comply:
-@value{op-bzip2} acts like @value{op-compress}, except that it uses
-the @code{bzip2} utility.
+First, when called without options, it should read data from standard
+input, compress it and output it on standard output.
-@table @kbd
-@item --compress
-@itemx --uncompress
-@itemx -z
-@itemx -Z
-When this option is specified, @command{tar} will compress (when
-writing an archive), or uncompress (when reading an archive). Used in
-conjunction with the @value{op-create}, @value{op-extract},
-@value{op-list} and @value{op-compare} operations.
+Secondly, if called with @option{-d} argument, it should do exactly
+the opposite, i.e., read the compressed data from the standard input
+and produce uncompressed data on the standard output.
@end table
-You can have archives be compressed by using the @value{op-gzip} option.
-This will arrange for @command{tar} to use the @command{gzip} program to be
-used to compress or uncompress the archive wren writing or reading it.
-
-To use the older, obsolete, @command{compress} program, use the
-@value{op-compress} option. The @acronym{GNU} Project recommends you not use
-@command{compress}, because there is a patent covering the algorithm it
-uses. You could be sued for patent infringement merely by running
-@command{compress}.
-
-I have one question, or maybe it's a suggestion if there isn't a way
-to do it now. I would like to use @value{op-gzip}, but I'd also like
+@FIXME{I have one question, or maybe it's a suggestion if there isn't a way
+to do it now. I would like to use @value{op-gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
to use :-)), basically adding ECC protection on top of compression.
Isn't that exactly the role of the @value{op-use-compress-prog} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
-way you want. It should recognize the @samp{-d} option, for when
+way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
It has been reported that if one writes compressed data (through the
@value{op-gzip} or @value{op-compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
-end up with less space on the tape.
+end up with less space on the tape.}
@node sparse
@subsection Archiving Sparse Files
@cindex Sparse Files
@UNREVISED
-@table @kbd
+@table @option
@item -S
@itemx --sparse
Handle sparse files efficiently.
@acronym{GNU} options. For now, it is an option needing to be specified on
the command line with the creation or updating of an archive.
-Files in the filesystem occasionally have ``holes.'' A hole in a file
+Files in the file system occasionally have ``holes.'' A hole in a file
is a section of the file's contents which was never written. The
contents of a hole read as all zeros. On many operating systems,
actual disk storage is not allocated for holes, but they are counted
archive for the file where the consecutive stretches of zeros are, and
only archives the ``real contents'' of the file. On extraction (using
@value{op-sparse} is not needed on extraction) any such files have
-hols created wherever the continuous stretches of zeros were found.
+holes created wherever the continuous stretches of zeros were found.
Thus, if you use @value{op-sparse}, @command{tar} archives won't take
more space than the original.
@command{tar} ignores the @value{op-sparse} option when reading an archive.
-@table @kbd
+@table @option
@item --sparse
@itemx -S
Files stored sparsely in the file system are represented sparsely in
@section Handling File Attributes
@UNREVISED
-When @command{tar} reads files, this causes them to have the access
-times updated. To have @command{tar} attempt to set the access times
-back to what they were before they were read, use the
-@value{op-atime-preserve} option.
+When @command{tar} reads files, it updates their access times. To
+avoid this, use the @value{op-atime-preserve} option, which can either
+reset the access time retroactively or avoid changing it in the first
+place.
Handling of file attributes
-@table @kbd
+@table @option
@item --atime-preserve
-Preserve access times on files that are read.
-This doesn't work for files that
-you don't own, unless you're root, and it doesn't interact with
-incremental dumps nicely (@pxref{Backups}), and it can set access or
-modification times incorrectly if other programs access the file while
-@command{tar} is running; but it is good enough for some purposes.
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+Preserve the access times of files that are read. This works only for
+files that you own, unless you have superuser privileges.
+
+@value{op-atime-preserve-replace} works on most systems, but it also
+restores the data modification time and updates the status change
+time. Hence it doesn't interact with incremental dumps nicely
+(@pxref{Backups}), and it can set access or data modification times
+incorrectly if other programs access the file while @command{tar} is
+running.
+
+@value{op-atime-preserve-system} avoids changing the access time in
+the first place, if the operating system supports this.
+Unfortunately, this may or may not work on any given operating system
+or file system. If @command{tar} knows for sure it won't work, it
+complains right away.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@value{op-atime-preserve-replace}, but this is intended to change to
+@value{op-atime-preserve-system} when the latter is better-supported.
@item -m
@itemx --touch
-Do not extract file modified time.
+Do not extract data modification time.
-When this option is used, @command{tar} leaves the modification times
-of the files it extracts as the time when the files were extracted,
-instead of setting it to the time recorded in the archive.
+When this option is used, @command{tar} leaves the data modification times
+of the files it extracts as the times when the files were extracted,
+instead of setting it to the times recorded in the archive.
This option is meaningless with @value{op-list}.
an emergency floppy with different passwd/group files for example.
It is otherwise impossible to extract files with the right ownerships
if the password file in use during the extraction does not match the
-one belonging to the filesystem(s) being extracted. This occurs,
+one belonging to the file system(s) being extracted. This occurs,
for example, if you are restoring your files after a major crash and
had booted from an emergency floppy with no password file or put your
disk into another machine to do the restore.
This option causes @command{tar} to set the modes (access permissions) of
extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
-on extracted files.
+on extracted files. This option is by default enabled when
+@command{tar} is executed by a superuser.
+
This option is meaningless with @value{op-list}.
@end table
@node Standard
-@section The Standard Format
+@section Basic Tar Format
@UNREVISED
While an archive may contain many files, the archive itself is a
@acronym{GNU} Emacs.
Physically, an archive consists of a series of file entries terminated
-by an end-of-archive entry, which consists of 512 zero bytes. A file
+by an end-of-archive entry, which consists of two 512 blocks of zero
+bytes. A file
entry usually describes one of the files in the archive (an
@dfn{archive member}), and consists of a file header and the contents
of the file. File headers contain file names and statistics, checksum
Each file archived is represented by a header block which describes
the file, followed by zero or more blocks which give the contents
-of the file. At the end of the archive file there may be a block
+of the file. At the end of the archive file there are two 512-byte blocks
filled with binary zeros as an end-of-file marker. A reasonable system
-should write a block of zeros at the end, but must not assume that
-such a block exists when reading an archive.
+should write such end-of-file marker at the end of an archive, but
+must not assume that such a block exists when reading an archive. In
+particular @GNUTAR{} always issues a warning if it does not encounter it.
The blocks may be @dfn{blocked} for physical I/O operations.
Each record of @var{n} blocks (where @var{n} is set by the
The @code{name}, @code{linkname}, @code{magic}, @code{uname}, and
@code{gname} are null-terminated character strings. All other fields
are zero-filled octal numbers in ASCII. Each numeric field of width
-@var{w} contains @var{w} minus 2 digits, a space, and a null, except
-@code{size}, and @code{mtime}, which do not contain the trailing null.
+@var{w} contains @var{w} minus 1 digits, and a null.
The @code{name} field is the file name of the file, with directory names
(if any) preceding the file name, separated by slashes.
permissions, the mode bit(s) specifying those special permissions
are ignored. Modes which are not supported by the operating system
restoring files from the archive will be ignored. Unsupported modes
-should be faked up when creating or updating an archive; e.g.@: the
+should be faked up when creating or updating an archive; e.g., the
group permission could be copied from the @emph{other} permission.
The @code{uid} and @code{gid} fields are the numeric user and group
are archived with this field specified as zero. @FIXME-xref{Modifiers, in
particular the @value{op-incremental} option.}
-The @code{mtime} field is the modification time of the file at the time
-it was archived. It is the ASCII representation of the octal value of
-the last time the file was modified, represented as an integer number of
+The @code{mtime} field is the data modification time of the file at
+the time it was archived. It is the ASCII representation of the octal
+value of the last time the file's contents were modified, represented
+as an integer number of
seconds since January 1, 1970, 00:00 Coordinated Universal Time.
The @code{chksum} field is the ASCII representation of the octal value
action occurs, @command{tar} issues a warning to the standard error.
The @code{atime} and @code{ctime} fields are used in making incremental
-backups; they store, respectively, the particular file's access time
-and last inode-change time.
+backups; they store, respectively, the particular file's access and
+status change times.
The @code{offset} is used by the @value{op-multi-volume} option, when
making a multi-volume archive. The offset is number of bytes into
@quotation
Is there any differences between the ability to recover crashed
-archives between the two of them. (Is there any chance of recovering
+archives between the two of them. (Is there any chance of recovering
crashed archives at all.)
@end quotation
@section Device Selection and Switching
@UNREVISED
-@table @kbd
+@table @option
@item -f [@var{hostname}:]@var{file}
@itemx --file=[@var{hostname}:]@var{file}
Use archive file or device @var{file} on @var{hostname}.
If the file name contains a @samp{:}, it is interpreted as
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
-sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
+sign (@samp{@@}), it is treated as @samp{user@@hostname:file name}. In
either case, @command{tar} will invoke the command @command{rsh} (or
-@command{remsh}) to start up an @file{/etc/rmt} on the remote machine. If
-you give an alternate login name, it will be given to the @command{rsh}.
-Naturally, the remote machine must have an executable @file{/etc/rmt}.
-This program is free software from the University of California, and a
-copy of the source code can be found with the sources for @command{tar};
-it's compiled and installed by default.
+@command{remsh}) to start up an @command{/usr/libexec/rmt} on the remote
+machine. If you give an alternate login name, it will be given to the
+@command{rsh}.
+Naturally, the remote machine must have an executable
+@command{/usr/libexec/rmt}. This program is free software from the
+University of California, and a copy of the source code can be found
+with the sources for @command{tar}; it's compiled and installed by default.
+The exact path to this utility is determined when configuring the package.
+It is @file{@var{prefix}/libexec/rmt}, where @var{prefix} stands for
+your installation prefix. This location may also be overridden at
+runtime by using @value{op-rmt-command} option (@xref{Option Summary,
+---rmt-command}, for detailed description of this option. @xref{Remote
+Tape Server}, for the description of @command{rmt} command).
If this option is not given, but the environment variable @env{TAPE}
is set, its value is used; otherwise, old versions of @command{tar}
too. The installer could also check for @samp{DEFTAPE} in
@file{<sys/mtio.h>}.
-@table @kbd
+@table @option
@item --force-local
Archive file is local even if it contains a colon.
@pindex rmt
In order to access the tape drive on a remote machine, @command{tar}
uses the remote tape server written at the University of California at
-Berkeley. The remote tape server must be installed as @file{/etc/rmt}
-on any machine whose tape drive you want to use. @command{tar} calls
-@file{/etc/rmt} by running an @command{rsh} or @command{remsh} to the remote
-machine, optionally using a different login name if one is supplied.
+Berkeley. The remote tape server must be installed as
+@file{@var{prefix}/libexec/rmt} on any machine whose tape drive you
+want to use. @command{tar} calls @command{rmt} by running an
+@command{rsh} or @command{remsh} to the remote machine, optionally
+using a different login name if one is supplied.
A copy of the source for the remote tape server is provided. It is
Copyright @copyright{} 1983 by the Regents of the University of
-California, but can be freely distributed. Instructions for compiling
-and installing it are included in the @file{Makefile}.
+California, but can be freely distributed. It is compiled and
+installed by default.
@cindex absolute file names
Unless you use the @value{op-absolute-names} option, @GNUTAR{}
The Unix man page on @command{tar} was totally confused about this.
When I wrote @code{PD TAR}, I used the historically correct terminology
(@command{tar} writes data records, which are grouped into blocks).
-It appears that the bogus terminology made it into @sc{posix} (no surprise
+It appears that the bogus terminology made it into @acronym{POSIX} (no surprise
here), and now Fran@,{c}ois has migrated that terminology back
into the source code too.
@end quotation
The data in an archive is grouped into blocks, which are 512 bytes.
Blocks are read and written in whole number multiples called
-@dfn{records}. The number of blocks in a record (ie. the size of a
+@dfn{records}. The number of blocks in a record (ie. the size of a
record in units of 512 bytes) is called the @dfn{blocking factor}.
The @value{op-blocking-factor} option specifies the blocking factor of
-an archive. The default blocking factor is typically 20 (ie.@:
+an archive. The default blocking factor is typically 20 (i.e.,
10240 bytes), but can be specified at installation. To find out
the blocking factor of an existing archive, use @samp{tar --list
--file=@var{archive-name}}. This may not work on some devices.
Records are separated by gaps, which waste space on the archive media.
If you are archiving on magnetic tape, using a larger blocking factor
(and therefore larger records) provides faster throughput and allows you
-to fit more data on a tape (because there are fewer gaps). If you are
+to fit more data on a tape (because there are fewer gaps). If you are
archiving on cartridge, a very large blocking factor (say 126 or more)
-greatly increases performance. A smaller blocking factor, on the other
+greatly increases performance. A smaller blocking factor, on the other
hand, may be useful when archiving small files, to avoid archiving lots
of nulls as @command{tar} fills out the archive to the end of the record.
In general, the ideal record size depends on the size of the
blocking factor (particularly if you're not sure what the blocking factor
is), you can usually use the @value{op-read-full-records} option while
specifying a blocking factor larger then the blocking factor of the archive
-(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
@xref{list}, for more information on the @value{op-list}
operation. @xref{Reading}, for a more detailed explanation of that option.
-@table @kbd
+@table @option
@item --blocking-factor=@var{number}
@itemx -b @var{number}
Specifies the blocking factor of an archive. Can be used with any
Device blocking
-@table @kbd
+@table @option
@item -b @var{blocks}
@itemx --blocking-factor=@var{blocks}
Set record size to @math{@var{blocks} * 512} bytes.
Apparently, Exabyte drives have a physical block size of 8K bytes.
If we choose our blocksize as a multiple of 8k bytes, then the problem
-seems to dissapper. Id est, we are using block size of 112 right
+seems to disappear. Id est, we are using block size of 112 right
now, and we haven't had the problem since we switched@dots{}
With @GNUTAR{} the blocking factor is limited only
drive unit that will be used to create the archives) sometimes lowers
the error rates observed at rewriting time.
-I might also use @samp{--number-blocks} instead of
-@samp{--block-number}, so @samp{--block} will then expand to
-@samp{--blocking-factor} unambiguously.
+I might also use @option{--number-blocks} instead of
+@option{--block-number}, so @option{--block} will then expand to
+@option{--blocking-factor} unambiguously.
@node Many
@section Many Archives on One Tape
data on the tape will be overwritten (unless it is no longer needed).
Before reading an archive, you should make sure the tape head is at
the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @FIXME{There is no such
-restore script!}@FIXME-xref{Scripted Restoration}@xref{mt}, for
+script will find the archive automatically. @FIXME-xref{Scripted Restoration}@xref{mt}, for
an explanation of the tape moving utility.
If you want to add new archive file entries to a tape, you should
@FIXME{is there any use for record operations?}
-@table @kbd
+@table @option
@item eof
@itemx weof
Writes @var{number} tape marks at the current position on the tape.
Moves tape position back @var{number} files.
@item rewind
-Rewinds the tape. (Ignores @var{number}).
+Rewinds the tape. (Ignores @var{number}).
@item offline
@itemx rewoff1
-Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
+Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
@item status
Prints status information about the tape unit.
successful, 1 if the command was unrecognized, and 2 if an operation
failed.
-@FIXME{New node on how to find an archive?}
-
-If you use @value{op-extract} with the @value{op-label} option specified,
-@command{tar} will read an archive label (the tape head has to be positioned
-on it) and print an error if the archive label doesn't match the
-@var{archive-name} specified. @var{archive-name} can be any regular
-expression. If the labels match, @command{tar} extracts the archive.
-@value{xref-label}.
-@FIXME-xref{Matching Format Parameters}@FIXME{fix cross
-references}@samp{tar --list --label} will cause @command{tar} to print the
-label.
-
-@FIXME{Program to list all the labels on a tape?}
-
@node Using Multiple Tapes
@section Using Multiple Tapes
@UNREVISED
Often you might want to write a large archive, one larger than will fit
on the actual tape you are using. In such a case, you can run multiple
@command{tar} commands, but this can be inconvenient, particularly if you
-are using options like @value{op-exclude} or dumping entire filesystems.
+are using options like @value{op-exclude} or dumping entire file systems.
Therefore, @command{tar} supports multiple tapes automatically.
Use @value{op-multi-volume} on the command line, and then @command{tar} will,
archive, complete in itself. For example, you can list or extract any
volume alone; just don't specify @value{op-multi-volume}. However, if one
file in the archive is split across volumes, the only way to extract
-it successfully is with a multi-volume extract command @samp{--extract
---multi-volume} (@samp{-xM}) starting on or before the volume where
+it successfully is with a multi-volume extract command @option{--extract
+--multi-volume} (@option{-xM}) starting on or before the volume where
the file begins.
For example, let's presume someone has two tape drives on a system
@menu
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
@end menu
@node Multi-Volume Archives
that volume), use @value{op-extract}, again without
@value{op-multi-volume}.
-If an archive member is split across volumes (ie. its entry begins on
+If an archive member is split across volumes (ie. its entry begins on
one volume of the media and ends on another), you need to specify
@value{op-multi-volume} to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
@FIXME{example}
@FIXME{There should be a sample program here, including an exit
-before end. Is the exit status even checked in tar? :-(}
+before end. Is the exit status even checked in tar? :-(}
-@table @kbd
+@table @option
@item --multi-volume
@itemx -M
Creates a multi-volume archive, when used in conjunction with
or such, for pushing a common date in all volumes or an archive set.
+@node Tarcat
+@subsection Concatenate Volumes into a Single Archive
+
+@pindex tarcat
+ Sometimes it is necessary to convert existing @GNUTAR{} multi-volume
+archive to a single @command{tar} archive. Simply concatenating all
+volumes into one will not work, since each volume carries an additional
+information at the beginning. @GNUTAR{} is shipped with the shell
+script @command{tarcat} designed for this purpose.
+
+ The script takes a list of files comprising a multi-volume archive
+and creates the resulting archive at the standard output. For example:
+
+@smallexample
+@kbd{tarcat vol.1 vol.2 vol.3 | tar tf -}
+@end smallexample
+
+ The script implements a simple heuristics to determine the format of
+the first volume file and to decide how to process the rest of the
+files. However, it makes no attempt to verify whether the files are
+given in order or even if they are valid @command{tar} archives.
+It uses @command{dd} and does not filter its standard error, so you
+will usually see lots of spurious messages.
+
+@FIXME{The script is not installed. Should we install it?}
+
@node label
@section Including a Label in the Archive
@cindex Labeling an archive
@cindex Labels on the archive media
@UNREVISED
-@table @kbd
-@item -V @var{name}
-@itemx --label=@var{name}
-Create archive with volume name @var{name}.
-@end table
-
-This option causes @command{tar} to write out a @dfn{volume header} at
-the beginning of the archive. If @value{op-multi-volume} is used, each
-volume of the archive will have a volume header of @samp{@var{name}
-Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
-next, and so on.
-
-@FIXME{Should the arg to --label be a quoted string?? No.}
-
-To avoid problems caused by misplaced paper labels on the archive
+@cindex @option{--label} option introduced
+@cindex @option{-V} option introduced
+ To avoid problems caused by misplaced paper labels on the archive
media, you can include a @dfn{label} entry---an archive member which
contains the name of the archive---in the archive itself. Use the
@value{op-label} option in conjunction with the @value{op-create} operation
to include a label entry in the archive as it is being created.
-If you create an archive using both @value{op-label} and
+@table @option
+@item --label=@var{archive-label}
+@itemx -V @var{archive-label}
+Includes an @dfn{archive-label} at the beginning of the archive when
+the archive is being created, when used in conjunction with the
+@value{op-create} operation. Checks to make sure the archive label
+matches the one specified (when used in conjunction with any other
+operation.
+@end table
+
+ If you create an archive using both @value{op-label} and
@value{op-multi-volume}, each volume of the archive will have an
archive label of the form @samp{@var{archive-label} Volume @var{n}},
where @var{n} is 1 for the first volume, 2 for the next, and so on.
@FIXME-xref{Multi-Volume Archives, for information on creating multiple
volume archives.}
-If you list or extract an archive using @value{op-label}, @command{tar} will
-print an error if the archive label doesn't match the @var{archive-label}
-specified, and will then not list nor extract the archive. In those cases,
-@var{archive-label} argument is interpreted as a globbing-style pattern
-which must match the actual magnetic volume label. @xref{exclude}, for
-a precise description of how match is attempted@footnote{Previous versions
-of @command{tar} used full regular expression matching, or before that, only
-exact string matching, instead of wildcard matchers. We decided for the
-sake of simplicity to use a uniform matching device through @command{tar}.}.
-If the switch @value{op-multi-volume} is being used, the volume label
-matcher will also suffix @var{archive-label} by @w{@samp{ Volume [1-9]*}}
-if the initial match fails, before giving up. Since the volume numbering
-is automatically added in labels at creation time, it sounded logical to
-equally help the user taking care of it when the archive is being read.
-
-The @value{op-label} was once called @samp{--volume}, but is not available
-under that name anymore.
-
-To find out an archive's label entry (or to find out if an archive has
-a label at all), use @samp{tar --list --verbose}. @command{tar} will
-print the label first, and then print archive member information, as
-in the example below:
+@cindex Volume label, listing
+@cindex Listing volume label
+ The volume label will be displayed by @option{--list} along with
+the file contents. If verbose display is requested, it will also be
+explicitely marked as in the example below:
@smallexample
+@group
$ @kbd{tar --verbose --list --file=iamanarchive}
V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
-rw-rw-rw- ringo user 40 1990-05-21 13:30 iamafilename
+@end group
@end smallexample
-@table @kbd
-@item --label=@var{archive-label}
-@itemx -V @var{archive-label}
-Includes an @dfn{archive-label} at the beginning of the archive when
-the archive is being created, when used in conjunction with the
-@value{op-create} option. Checks to make sure the archive label
-matches the one specified (when used in conjunction with the
-@value{op-extract} option.
-@end table
+@cindex @option{--test-label} option introduced
+@anchor{--test-label option}
+ However, @option{--list} option will cause listing entire
+contents of the archive, which may be undesirable (for example, if the
+archive is stored on a tape). You can request checking only the volume
+by specifying @option{--test-label} option. This option reads only the
+first block of an archive, so it can be used with slow storage
+devices. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive}
+iamalabel
+@end group
+@end smallexample
+
+ If @option{--test-label} is used with a single command line
+argument, @command{tar} compares the volume label with the
+argument. It exits with code 0 if the two strings match, and with code
+2 otherwise. In this case no output is displayed. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable'}
+@result{} 0
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable' alabel}
+@result{} 1
+@end group
+@end smallexample
+
+ If you request any operation, other than @option{--create}, along
+with using @option{--label} option, @command{tar} will first check if
+the archive label matches the one specified and will refuse to proceed
+if it does not. Use this as a safety precaution to avoid accidentally
+overwriting existing archives. For example, if you wish to add files
+to @file{archive}, presumably labelled with string @samp{My volume},
+you will get:
-To get a common information on all tapes of a series, use the
-@value{op-label} option. For having this information different in each
+@smallexample
+@group
+$ @kbd{tar -rf archive --label 'My volume' .}
+tar: Archive not labeled to match `My volume'
+@end group
+@end smallexample
+
+@noindent
+in case its label does not match. This will work even if
+@file{archive} is not labelled at all.
+
+ Similarly, @command{tar} will refuse to list or extract the
+archive if its label doesn't match the @var{archive-label}
+specified. In those cases, @var{archive-label} argument is interpreted
+as a globbing-style pattern which must match the actual magnetic
+volume label. @xref{exclude}, for a precise description of how match
+is attempted@footnote{Previous versions of @command{tar} used full
+regular expression matching, or before that, only exact string
+matching, instead of wildcard matchers. We decided for the sake of
+simplicity to use a uniform matching device through
+@command{tar}.}. If the switch @value{op-multi-volume} is being used,
+the volume label matcher will also suffix @var{archive-label} by
+@w{@samp{ Volume [1-9]*}} if the initial match fails, before giving
+up. Since the volume numbering is automatically added in labels at
+creation time, it sounded logical to equally help the user taking care
+of it when the archive is being read.
+
+ The @value{op-label} was once called @option{--volume}, but is not available
+under that name anymore.
+
+ You can also use @option{--label} to get a common information on
+all tapes of a series. For having this information different in each
series created through a single script used on a regular basis, just
manage to get some date string as part of the label. For example:
@smallexample
+@group
$ @kbd{tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"}
$ @kbd{tar --create --file=/dev/tape --multi-volume \
--volume="Daily backup for `date +%Y-%m-%d`"}
+@end group
@end smallexample
-Also note that each label has its own date and time, which corresponds
+ Also note that each label has its own date and time, which corresponds
to when @GNUTAR{} initially attempted to write it,
often soon after the operator launches @command{tar} or types the
carriage return telling that the next tape is ready. Comparing date
rewinding tapes and the operator switching them were negligible, which
is usually not the case.
-@FIXME{was --volume}
-
@node verify
@section Verifying Data as It is Stored
@cindex Verifying a write operation
@cindex Double-checking a write operation
-@table @kbd
+@table @option
@item -W
@itemx --verify
Attempt to verify the archive after writing.
@appendix Free Software Needs Free Documentation
@include freemanuals.texi
+@node Genfile
+@appendix Genfile
+@include genfile.texi
+
+@node Snapshot Files
+@appendix Format of the Incremental Snapshot Files
+@include snapshot.texi
+
@node Copying This Manual
@appendix Copying This Manual
projects / chaz / tar / blobdiff