* Changes::
* Configuring Help Summary::
+* Fixing Snapshot Files::
* Tar Internals::
* Genfile::
* Free Software Needs Free Documentation::
Controlling the Archive Format
-* Portability:: Making @command{tar} Archives More Portable
* Compression:: Using Less Space through Compression
* Attributes:: Handling File Attributes
+* Portability:: Making @command{tar} Archives More Portable
* cpio:: Comparison of @command{tar} and @command{cpio}
+Using Less Space through Compression
+
+* gzip:: Creating and Reading Compressed Archives
+* sparse:: Archiving Sparse Files
+
Making @command{tar} Archives More Portable
* Portable Names:: Portable Names
* Split Recovery:: Members Split Between Volumes
* Sparse Recovery:: Sparse Members
-Using Less Space through Compression
-
-* gzip:: Creating and Reading Compressed Archives
-* sparse:: Archiving Sparse Files
-
Tapes and Other Archive Media
* Device:: Device selection and switching
available on some systems. However, mounting typically requires
superuser privileges and can be a pain to manage.
+@opsummary{auto-compress}
+@item --auto-compress
+@itemx -a
+
+During a @option{--create} operation, enables automatic compressed
+format recognition based on the archive suffix. @xref{gzip}.
+
@opsummary{backup}
@item --backup=@var{backup-type}
Exclude from dump any directory containing file named @var{file}.
@xref{exclude}.
+@opsummary{exclude-vcs}
+@item --exclude-vcs
+
+Exclude from dump directories and files, that are internal for some
+widely used version control systems.
+
+@xref{exclude}.
+
@opsummary{file}
@item --file=@var{archive}
@itemx -f @var{archive}
With other operations, informs @command{tar} that the archive is in
incremental format. @xref{Incremental Dumps}.
+@opsummary{lzma}
+@item --lzma
+
+This option tells @command{tar} to read or write archives through
+@command{lzma}. @xref{gzip}.
+
@opsummary{mode}
@item --mode=@var{permissions}
(see --info-script)
-@opsummary{seek}
-@item --seek
-@itemx -n
-
-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.
-
@opsummary{newer}
@item --newer=@var{date}
@itemx --after-date=@var{date}
This option does not affect extraction from archives.
-@opsummary{transform}
-@item --transform=@var{sed-expr}
-
-Transform file or member names using @command{sed} replacement expression
-@var{sed-expr}. For example,
-
-@smallexample
-$ @kbd{tar cf archive.tar --transform 's,^\./,usr/,' .}
-@end smallexample
-
-@noindent
-will add to @file{archive} files from the current working directory,
-replacing initial @samp{./} prefix with @samp{usr/}. For the detailed
-discussion, @xref{transform}.
-
-To see transformed member names in verbose listings, use
-@option{--show-transformed-names} option
-(@pxref{show-transformed-names}).
-
-@opsummary{quote-chars}
-@item --quote-chars=@var{string}
-Always quote characters from @var{string}, even if the selected
-quoting style would not quote them (@pxref{quoting styles}).
-
-@opsummary{quoting-style}
-@item --quoting-style=@var{style}
-Set quoting style to use when printing member and file names
-(@pxref{quoting styles}). Valid @var{style} values are:
-@code{literal}, @code{shell}, @code{shell-always}, @code{c},
-@code{escape}, @code{locale}, and @code{clocale}. Default quoting
-style is @code{escape}, unless overridden while configuring the
-package.
-
@opsummary{pax-option}
@item --pax-option=@var{keyword-list}
This option is meaningful only with @acronym{POSIX.1-2001} archives
Specifying this option instructs @command{tar} that it should use the
permissions directly from the archive. @xref{Setting Access Permissions}.
+@opsummary{quote-chars}
+@item --quote-chars=@var{string}
+Always quote characters from @var{string}, even if the selected
+quoting style would not quote them (@pxref{quoting styles}).
+
+@opsummary{quoting-style}
+@item --quoting-style=@var{style}
+Set quoting style to use when printing member and file names
+(@pxref{quoting styles}). Valid @var{style} values are:
+@code{literal}, @code{shell}, @code{shell-always}, @code{c},
+@code{escape}, @code{locale}, and @code{clocale}. Default quoting
+style is @code{escape}, unless overridden while configuring the
+package.
+
@opsummary{read-full-records}
@item --read-full-records
@itemx -B
(See @option{--preserve-permissions}; @pxref{Setting Access Permissions}.)
+@opsummary{seek}
+@item --seek
+@itemx -n
+
+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.
+
@opsummary{show-defaults}
@item --show-defaults
rather than the data modification time stored in the archive.
@xref{Data Modification Times}.
+@opsummary{transform}
+@item --transform=@var{sed-expr}
+
+Transform file or member names using @command{sed} replacement expression
+@var{sed-expr}. For example,
+
+@smallexample
+$ @kbd{tar cf archive.tar --transform 's,^\./,usr/,' .}
+@end smallexample
+
+@noindent
+will add to @file{archive} files from the current working directory,
+replacing initial @samp{./} prefix with @samp{usr/}. For the detailed
+discussion, @xref{transform}.
+
+To see transformed member names in verbose listings, use
+@option{--show-transformed-names} option
+(@pxref{show-transformed-names}).
+
@opsummary{uncompress}
@item --uncompress
with the @option{--atime-preserve=replace} option), or if you set the clock
backwards.
+@cindex Device numbers, using in incremental backups
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
comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
+If you are using the @i{Linux} kernel, the device numbers can also
+change when upgrading to some newer versions of the kernel. This can
+cause the next backup to be full backup on the affected filesystems.
+@xref{Fixing Snapshot Files}, for the information on how to handle this case.
+
Note that incremental archives use @command{tar} extensions and may
not be readable by non-@acronym{GNU} versions of the @command{tar} program.
single line @file{*.o}, no files whose names end in @file{.o} will be
added to the archive.
+Notice, that lines from @var{file} are read verbatim. One of the
+frequent errors is leaving some extra whitespace after a file name,
+which is difficult to catch using text editors.
+
+However, empty lines are OK.
+
+@cindex version control system, excluding files
+@cindex VCS, excluding files
+@cindex SCCS, excluding files
+@cindex RCS, excluding files
+@cindex CVS, excluding files
+@cindex SVN, excluding files
+@cindex git, excluding files
+@table @option
+@opindex exclude-vcs
+@item --exclude-vcs
+Exclude files and directories used by some version control systems.
+@end table
+
+As of version @value{VERSION}, the following files are excluded:
+
+@itemize @bullet
+@item @file{CVS/}, and everything under it
+@item @file{RCS/}, and everything under it
+@item @file{SCCS/}, and everything under it
+@item @file{.git/}, and everything under it
+@item @file{.gitignore}
+@item @file{.cvsignore}
+@item @file{.svn/}, and everything under it
+@item @file{.arch-ids/}, and everything under it
+@item @file{@{arch@}/}, and everything under it
+@item @file{=RELEASE-ID}
+@item @file{=meta-update}
+@item @file{=update}
+@end itemize
+
@findex exclude-caches
When creating an archive, the @option{--exclude-caches} option family
causes @command{tar} to exclude all directories that contain a @dfn{cache
use to hold regenerable, non-precious data, so that such data can be
more easily excluded from backups.
-There are three @samp{exclude-caches} option, providing a different
+There are three @samp{exclude-caches} options, each providing a different
exclusion semantics:
@table @option
@cindex Storing archives in compressed format
@GNUTAR{} is able to create and read compressed archives. It supports
-@command{gzip} and @command{bzip2} compression programs. For backward
-compatibility, 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}.
+@command{gzip}, @command{bzip2} and @command{lzma} compression
+programs. For backward compatibility, 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 by far less effective than other
+compression programs.
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{--bzip2}) to create a @command{bzip2} compressed archive,
+@command{lzma} to create an @asis{LZMA} compressed archive and
@option{-Z} (@option{--compress}) to use @command{compress} program.
For example:
$ @kbd{tar cfz archive.tar.gz .}
@end smallexample
+You can also let @GNUTAR{} select the compression program basing on
+the suffix of the archive file name. This is done using
+@option{--auto-compress} (@option{-a}) command line option. For
+example, the following invocation will use @command{bzip2} for
+compression:
+
+@smallexample
+$ @kbd{tar cfa archive.tar.bz2 .}
+@end smallexample
+
+@noindent
+whereas the following one will use @command{lzma}:
+
+@smallexample
+$ @kbd{tar cfa archive.tar.lzma .}
+@end smallexample
+
+For a complete list of file name suffixes recognized by @GNUTAR{},
+@ref{auto-compress}.
+
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
The following table summarizes compression options used by @GNUTAR{}.
@table @option
+@anchor{auto-compress}
+@opindex auto-compress
+@item --auto-compress
+@itemx -a
+Select a compression program to use by the archive file name
+suffix. The following suffixes are recognized:
+
+@multitable @columnfractions 0.3 0.6
+@headitem Suffix @tab Compression program
+@item @samp{.gz} @tab @command{gzip}
+@item @samp{.tgz} @tab @command{gzip}
+@item @samp{.taz} @tab @command{gzip}
+@item @samp{.Z} @tab @command{compress}
+@item @samp{.taZ} @tab @command{compress}
+@item @samp{.bz2} @tab @command{bzip2}
+@item @samp{.tz2} @tab @command{bzip2}
+@item @samp{.tbz2} @tab @command{bzip2}
+@item @samp{.tbz} @tab @command{bzip2}
+@item @samp{.lzma} @tab @command{lzma}
+@item @samp{.tlz} @tab @command{lzma}
+@end multitable
+
@opindex gzip
@opindex ungzip
@item -z
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @option{--gzip}.
+@opindex lzma
+@item --lzma
+Filter the archive through @command{lzma}. Otherwise like @option{--gzip}.
+
@opindex compress
@opindex uncompress
@item -Z
@end group
@end smallexample
-The same script cant be used while listing, comparing or extracting
+The same script can be used while listing, comparing or extracting
from the created archive. For example:
@smallexample
Right margin of the text output. Used for wrapping.
@end deftypevr
+@node Fixing Snapshot Files
+@appendix Fixing Snapshot Files
+@include tar-snapshot-edit.texi
+
@node Tar Internals
@appendix Tar Internals
@include intern.texi
projects / chaz / tar / blobdiff