@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 both at the same time, is a good way to proceed.
@c ---------------------------------------------------------------------
@c Output marks for nodes needing revision, but not in PUBLISH rendition.
@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 ref-keep-old-files @ref{Keep Old Files}
+@set xref-keep-old-files @xref{Keep Old Files}
+@set pxref-keep-old-files @pxref{Keep Old Files}
+
+@set op-keep-newer-files @kbd{--keep-old-files}
+@set ref-keep-newer-files @ref{Keep Newer Files}
+@set xref-keep-newer-files @xref{Keep Newer Files}
+@set pxref-keep-newer-files @pxref{Keep Newer Files}
@set op-label @kbd{--label=@var{archive-label}} (@kbd{-V @var{archive-label}})
@set ref-label @ref{label}
@set xref-owner @xref{Option Summary}
@set pxref-owner @pxref{Option Summary}
-@set op-format @kbd{--format}
+@set op-format @kbd{--format} (@kbd{-H})
@set ref-format @ref{format}
@set xref-format @xref{format}
@set pxref-format @pxref{format}
@set op-format-gnu @kbd{--format=gnu}
@set op-format-oldgnu @kbd{--format=oldgnu}
@set op-format-posix @kbd{--format=posix}
+@set op-format-ustar @kbd{--format=ustar}
@set op-posix @kbd{--posix}
@set ref-posix @ref{posix}
@set xref-remove-files @xref{Writing}
@set pxref-remove-files @pxref{Writing}
+@set op-rmt-command @kbd{rmt-command=@var{command}}
@set op-rsh-command @kbd{rsh-command=@var{command}}
@set op-same-order @kbd{--same-order} (@kbd{--preserve-order}, @kbd{-s})
@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-strip-components @kbd{--strip-components}
+@set ref-strip-components @ref{--strip-components}
+@set xref-strip-components @xref{--strip-components}
+@set pxref-strip-components @pxref{--strip-components}
@set op-suffix @kbd{--suffix=@var{suffix}}
@set ref-suffix @ref{Backup options}
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}
* 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
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
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}
* 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.
@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
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 synonym for @option{--old-archive}.
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
-synonym 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
synonym for @samp{--one-file-system}. Such usage is deprecated.
For compatibility with other implementations future versions of
@option{--check-links}.
@item Use of options @option{--portability} and @option{--old-archive}
+
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.
@end table
@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 maintenance work has started
+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.
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}
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:
-
-@smallexample
-This is an example of a line which would otherwise not fit in this space.
-@end smallexample
+sometimes @samp{like this}.
-@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
(they are @dfn{file name arguments} to the @samp{--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
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
@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
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 beginnig 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
(@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
@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
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
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 @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 any of the following notations:
+@samp{--file=archive.tar} or @samp{--file archive.tar}.
+
+In contrast, optional arguments must always be introduced using
+an equal sign. For example, the @samp{--backup} option takes
+an optional argument specifying backup type. It must be used
+as @samp{--backup=@var{backup-type}}.
@node Short Options
@subsection Short Option Style
@w{@samp{-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
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}.
@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},
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
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
+@item 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
+@item 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
Synonym for @option{--format=v7}.
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
(See @samp{--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
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
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
+@samp{--verbose}.
+
@item --verbose
@itemx -v
@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.
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.}
-
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
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
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
(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
* Dealing with Old Files::
* Overwrite Old Files::
* Keep Old Files::
+* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
* Modification Times::
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
extraction.
@end table
+@node Keep Newer Files
+@unnumberedsubsubsec Keep Newer Files
+
+@table @kbd
+@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
@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=-)}}
@end smallexample
@end ifclear
-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
@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}, and
+@value{xref-listed-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.
+
+@menu
+* General-Purpose Variables::
+* Magnetic Tape Control::
+* User Hooks::
+* backup-specs example:: An Example Text of @file{Backup-specs}
+@end menu
-@FIXME-xref{Script Syntax, for an explanation of this syntax.}
+@node General-Purpose Variables
+@subsection General-Purpose Variables
-@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:}
+@defvr {Backup variable} ADMINISTRATOR
+The user name of the backup administrator. @code{Backup} scripts
+sends a backup report to this address.
+@end defvr
-@table @samp
-@item ADMINISTRATOR
-The user name of the backup administrator.
+@defvr {Backup variable} BACKUP_HOUR
+The hour at which the backups are done. This can be a number from 0
+to 23, or the time specification in form @var{hours}:@var{minutes},
+or the string @samp{now}.
-@item BACKUP_HOUR
-The hour at which the backups are done. This can be a number from 0
-to 23, or the string @samp{now}.
+This variable is used by @code{backup}. Its value may be overridden
+using @option{--time} option (@pxref{Scripted Backups}).
+@end defvr
-@item TAPE_FILE
+@defvr {Backup variable} 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.
+@end defvr
-@FIXME{examples for all ...}
-
-@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}.
+@defvr {Backup variable} BLOCKING
-@item BLOCKING
The blocking factor @command{tar} will use when writing the dump archive.
@value{xref-blocking-factor}.
+@end defvr
-@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
+@defvr {Backup variable} BACKUP_DIRS
+
+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 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
+
+@defvr {Backup variable} DIRLIST
+
+A path to the file containing the list of the filesystems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
+@end defvr
+
+@defvr {Backup variable} BACKUP_FILES
+
+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.
+
+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
+
+@defvr {Backup variable} FILELIST
+
+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
+
+@defvr {Backup variable} RSH
+
+Path to @code{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
+
+@defvr {Backup variable} RSH_COMMAND
+
+Path to rsh binary on remote mashines. This will be passed via
+@option{--rsh-command} option to the remote invocation of @GNUTAR{}.
+@end defvr
+
+@defvr {Backup variable} VOLNO_FILE
+
+Name of temporary file to hold volume numbers. This needs to be accessible
+by all the machines which have filesystems 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 filesystems
+
+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
-@FIXME{Same file name, be specific. Through NFS ...}
+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
+
+Pathname 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 filesystem being dumped or restored.
+
+@item fsname
+Filesystem name with directory separators replaced with colons. This
+is useful e.g. for creating unique files.
@end table
+@end deffn
-@menu
-* backup-specs example:: An Example Text of @file{Backup-specs}
-* Script Syntax:: Syntax for @file{Backup-specs}
-@end menu
+Following variables keep the names of user hook functions
+
+@defvr {Backup variable} DUMP_BEGIN
+Dump begin function. It is executed before dumping the filesystem.
+@end defvr
+
+@defvr {Backup variable} DUMP_END
+Executed after dumping the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_BEGIN
+Executed before restoring the filesystem.
+@end defvr
+
+@defvr {Backup variable} RESTORE_END
+Executed after restoring the filesystem.
+@end defvr
@node backup-specs example
@subsection An Example Text of @file{Backup-specs}
-@UNREVISED
-The following is the text of @file{backup-specs} as it appears at FSF:
+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
-TAPE_STATUS="mts -t $TAPE_FILE"
+
+# 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
@end smallexample
-@node Script Syntax
-@subsection Syntax for @file{Backup-specs}
-@UNREVISED
-
-@file{backup-specs} is in shell script syntax. The following
-conventions should be considered when editing the script:
-@FIXME{"conventions?"}
-
-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.
-
-A quoted string typically cannot contain wildcards. In
-@file{backup-specs}, however, the parameters BACKUP_DIRS and
-BACKUP_FILES can contain wildcards.
-
@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 @command{restore} without options, it will
+then restore all the filesystems 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 filesystems (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 filesystems 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 filesystems on the machine @samp{albert}
+as well as @file{/var} filesystem 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
+
+The full list of options accepted by @code{restore} follows:
+
+@table @option
+@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.
-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.
+@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.
@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
-
@node Choosing
@chapter Choosing Files and Names for @command{tar}
@UNREVISED
(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,
@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
@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
+@item 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
* 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
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}.
@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.
@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.
-
-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.
+to read and create archives conforming to @acronym{POSIX.1-2001} standard.
+A @acronym{POSIX} conformant archive will be created if @command{tar}
+was given @value{op-format-posix} option.
Notice, that currently @acronym{GNU} extensions are not
allowed with this format. Following is the list of options that
cannot be used with @value{op-format-posix}:
@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.
@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
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
+@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
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
@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.
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
sign (@kbd{@@}), 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}
@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
projects / chaz / tar / blobdiff