@include value.texi
@defcodeindex op
+@defcodeindex kw
@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
@syncodeindex ky cp
@syncodeindex pg cp
@syncodeindex vr cp
+@syncodeindex kw cp
@copying
* defaults::
* verbose::
* checkpoints::
+* warnings::
* interactive::
The Three Option Styles
@node extract
@section How to Extract Members from an Archive
-@UNREVISED
@cindex Extraction
@cindex Retrieving files from an archive
@cindex Resurrecting files from an archive
@node tar invocation
@chapter Invoking @GNUTAR{}
-@UNREVISED
This chapter is about how one invokes the @GNUTAR{}
command, from the command synopsis (@pxref{Synopsis}). There are
* defaults::
* verbose::
* checkpoints::
+* warnings::
* interactive::
@end menu
@node Long Options
@subsection Long Option Style
+@cindex long options
+@cindex options, long style
+@cindex options, GNU style
+@cindex options, mnemonic names
Each option has at least one @dfn{long} (or @dfn{mnemonic}) name starting with two
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
gives a fairly good set of hints about what the command does, even
for those not fully acquainted with @command{tar}.
+@cindex arguments to long options
+@cindex long options with mandatory arguments
Long options which require arguments take those arguments
immediately following the option name. There are two ways of
specifying a mandatory argument. It can be separated from the
@file{archive.tar} as argument by using any of the following notations:
@option{--file=archive.tar} or @option{--file archive.tar}.
+@cindex optional arguments to long options
+@cindex long options with optional arguments
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
@node Short Options
@subsection Short Option Style
+@cindex short options
+@cindex options, short style
+@cindex options, traditional
Most options also have a @dfn{short option} name. Short options start with
a single dash, and are followed by a single character, e.g., @option{-t}
(which is equivalent to @option{--list}). The forms are absolutely
The short option names are faster to type than long option names.
+@cindex arguments to short options
+@cindex short options with mandatory arguments
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
@w{@option{-f @var{archive-name}}} denote the option which indicates a
specific archive, here named @file{archive.tar}.
+@cindex optional arguments to short options
+@cindex short options with optional arguments
Short options which take optional arguments take their arguments
immediately following the option letter, @emph{without any intervening
white space characters}.
@node Old Options
@subsection Old Option Style
-@UNREVISED
+@cindex options, old style
+@cindex old option style
Like short options, @dfn{old options} are single letters. However, old options
must be written together as a single clumped set, without spaces separating
long option @option{--list}. So for example, the command @w{@samp{tar
cv}} specifies the option @option{-v} in addition to the operation @option{-c}.
+@cindex arguments to old options
+@cindex old options with mandatory arguments
When options that need arguments are given together with the command,
all the associated arguments follow, in the same order as the options.
Thus, the example given previously could also be written in the old
@node Mixing
@subsection Mixing Option Styles
+@cindex options, mixing different styles
All three styles may be intermixed in a single @command{tar} command,
so long as the rules for each style are fully
respected@footnote{Before @GNUTAR{} version 1.11.6,
want a visual indication that @command{tar} is still running, but
don't want to see @option{--verbose} output. You can also instruct
@command{tar} to execute a list of actions on each checkpoint, see
-@option{--checklist-action} below. For a detailed description, see
+@option{--checkpoint-action} below. For a detailed description, see
@ref{checkpoints}.
@opsummary{checkpoint-action}
When performing operations, @command{tar} will skip files that match
@var{pattern}. @xref{exclude}.
+@opsummary{exclude-backups}
+@item --exclude-backups
+Exclude backup and lock files. @xref{exclude,, exclude-backups}.
+
@opsummary{exclude-from}
@item --exclude-from=@var{file}
@itemx -X @var{file}
Exclude from dump any directory containing a valid cache directory
tag file, but still dump the directory node and the tag file itself.
-@xref{exclude}.
+@xref{exclude,, exclude-caches}.
@opsummary{exclude-caches-under}
@item --exclude-caches-under
@item --exclude-tag=@var{file}
Exclude from dump any directory containing file named @var{file}, but
-dump the directory node and @var{file} itself. @xref{exclude}.
+dump the directory node and @var{file} itself. @xref{exclude,, exclude-tag}.
@opsummary{exclude-tag-under}
@item --exclude-tag-under=@var{file}
Exclude from dump the contents of any directory containing file
-named @var{file}, but dump the directory node itself. @xref{exclude}.
+named @var{file}, but dump the directory node itself. @xref{exclude,,
+exclude-tag-under}.
@opsummary{exclude-tag-all}
@item --exclude-tag-all=@var{file}
Exclude from dump any directory containing file named @var{file}.
-@xref{exclude}.
+@xref{exclude,,exclude-tag-all}.
@opsummary{exclude-vcs}
@item --exclude-vcs
Exclude from dump directories and files, that are internal for some
widely used version control systems.
-@xref{exclude}.
+@xref{exclude,,exclude-vcs}.
@opsummary{file}
@item --file=@var{archive}
@command{tar} will only operate on archives that have a label matching
the pattern specified in @var{name}. @xref{Tape Files}.
+@opsummary{level}
+@item --level=@var{n}
+Force incremental backup of level @var{n}. As of @GNUTAR version
+@value{VERSION}, the option @option{--level=0} truncates the snapshot
+file, thereby forcing the level 0 dump. Other values of @var{n} are
+effectively ignored. @xref{--level=0}, for details and examples.
+
+The use of this option is valid only in conjunction with the
+@option{--listed-incremental} option. @xref{Incremental Dumps},
+for a detailed description.
+
@opsummary{listed-incremental}
@item --listed-incremental=@var{snapshot-file}
@itemx -g @var{snapshot-file}
With other operations, informs @command{tar} that the archive is in
incremental format. @xref{Incremental Dumps}.
+@opsummary{lzip}
+@item --lzip
+
+This option tells @command{tar} to read or write archives through
+@command{lzip}. @xref{gzip}.
+
@opsummary{lzma}
@item --lzma
the permissions specified in the archive. This is the default behavior
for ordinary users.
+@opsummary{no-seek}
+@item --no-seek
+
+The archive media does not support seeks to arbitrary
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. Use this option to disable this
+mechanism.
+
@opsummary{no-unquote}
@item --no-unquote
Treat all input file or member names literally, do not interpret
@opsummary{pax-option}
@item --pax-option=@var{keyword-list}
-This option is meaningful only with @acronym{POSIX.1-2001} archives
-(@pxref{posix}). It modifies the way @command{tar} handles the
+This option enables creation of the archive in @acronym{POSIX.1-2001}
+format (@pxref{posix}) and modifies the way @command{tar} handles the
extended header keywords. @var{Keyword-list} is a comma-separated
list of keyword options. @xref{PAX keywords}, for a detailed
discussion.
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.
+in cases when such recognition fails. It takes effect only if the
+archive is open for reading (e.g. with @option{--list} or
+@option{--extract} options).
@opsummary{show-defaults}
@item --show-defaults
keep track of which volume of a multi-volume archive it is working in
@var{file}. @xref{volno-file}.
+@opsummary{warning}
+@item --warning=@var{keyword}
+
+Enable or disable warning messages identified by @var{keyword}. The
+messages are suppressed if @var{keyword} is prefixed with @samp{no-}.
+@xref{warnings}.
+
@opsummary{wildcards}
@item --wildcards
Use wildcards when matching member names with patterns.
@option{--checkpoint}. In this case, the default checkpoint frequency
(at each 10th record) is assumed.
+@node warnings
+@section Controlling Warning Messages
+
+Sometimes, while performing the requested task, @GNUTAR{} notices
+some conditions that are not exactly erros, but which the user
+should be aware of. When this happens, @command{tar} issues a
+@dfn{warning message} describing the condition. Warning messages
+are output to the standard error and they do not affect the exit
+code of @command{tar} command.
+
+@xopindex{warning, explained}
+@GNUTAR{} allows the user to suppress some or all of its warning
+messages:
+
+@table @option
+@item --warning=@var{keyword}
+Control display of the warning messages identified by @var{keyword}.
+If @var{keyword} starts with the prefix @samp{no-}, such messages are
+suppressed. Otherwise, they are enabled.
+
+Multiple @option{--warning} messages accumulate.
+
+The tables below list allowed values for @var{keyword} along with the
+warning messages they control.
+@end table
+
+@subheading Keywords controlling @command{tar} operation
+@table @asis
+@kwindex all
+@item all
+Enable all warning messages. This is the default.
+@kwindex none
+@item none
+Disable all warning messages.
+@kwindex filename-with-nuls
+@cindex @samp{file name read contains nul character}, warning message
+@item filename-with-nuls
+@samp{%s: file name read contains nul character}
+@kwindex alone-zero-block
+@cindex @samp{A lone zero block at}, warning message
+@item alone-zero-block
+@samp{A lone zero block at %s}
+@end table
+
+@subheading Keywords applicable for @command{tar --create}
+@table @asis
+@kwindex cachedir
+@cindex @samp{contains a cache directory tag}, warning message
+@item cachedir
+@samp{%s: contains a cache directory tag %s; %s}
+@kwindex file-shrank
+@cindex @samp{File shrank by %s bytes}, warning message
+@item file-shrank
+@samp{%s: File shrank by %s bytes; padding with zeros}
+@kwindex xdev
+@cindex @samp{file is on a different filesystem}, warning message
+@item xdev
+@samp{%s: file is on a different filesystem; not dumped}
+@kwindex file-ignored
+@cindex @samp{Unknown file type; file ignored}, warning message
+@cindex @samp{socket ignored}, warning message
+@cindex @samp{door ignored}, warning message
+@item file-ignored
+@samp{%s: Unknown file type; file ignored}
+@samp{%s: socket ignored}
+@*@samp{%s: door ignored}
+@kwindex file-unchanged
+@cindex @samp{file is unchanged; not dumped}, warning message
+@item file-unchanged
+@samp{%s: file is unchanged; not dumped}
+@kwindex ignore-archive
+@cindex @samp{file is the archive; not dumped}, warning message
+@kwindex ignore-archive
+@cindex @samp{file is the archive; not dumped}, warning message
+@item ignore-archive
+@samp{%s: file is the archive; not dumped}
+@kwindex file-removed
+@cindex @samp{File removed before we read it}, warning message
+@item file-removed
+@samp{%s: File removed before we read it}
+@kwindex file-changed
+@cindex @samp{file changed as we read it}, warning message
+@item file-changed
+@samp{%s: file changed as we read it}
+@end table
+
+@subheading Keywords applicable for @command{tar --extract}
+@table @asis
+@kwindex timestamp
+@cindex @samp{implausibly old time stamp %s}, warning message
+@cindex @samp{time stamp %s is %s s in the future}, warning message
+@item timestamp
+@samp{%s: implausibly old time stamp %s}
+@*@samp{%s: time stamp %s is %s s in the future}
+@kwindex contiguous-cast
+@cindex @samp{Extracting contiguous files as regular files}, warning message
+@item contiguous-cast
+@samp{Extracting contiguous files as regular files}
+@kwindex symlink-cast
+@cindex @samp{Attempting extraction of symbolic links as hard links}, warning message
+@item symlink-cast
+@samp{Attempting extraction of symbolic links as hard links}
+@kwindex unknown-cast
+@cindex @samp{Unknown file type `%c', extracted as normal file}, warning message
+@item unknown-cast
+@samp{%s: Unknown file type `%c', extracted as normal file}
+@kwindex ignore-newer
+@cindex @samp{Current %s is newer or same age}, warning message
+@item ignore-newer
+@samp{Current %s is newer or same age}
+@kwindex unknown-keyword
+@cindex @samp{Ignoring unknown extended header keyword `%s'}, warning message
+@item unknown-keyword
+@samp{Ignoring unknown extended header keyword `%s'}
+@end table
+
+@subheading Keywords controlling incremental extraction:
+@table @asis
+@kwindex rename-directory
+@cindex @samp{%s: Directory has been renamed from %s}, warning message
+@cindex @samp{%s: Directory has been renamed}, warning message
+@item rename-directory
+@samp{%s: Directory has been renamed from %s}
+@*@samp{%s: Directory has been renamed}
+@kwindex new-directory
+@cindex @samp{%s: Directory is new}, warning message
+@item new-directory
+@samp{%s: Directory is new}
+@kwindex xdev
+@cindex @samp{%s: directory is on a different device: not purging}, warning message
+@item xdev
+@samp{%s: directory is on a different device: not purging}
+@kwindex bad-dumpdir
+@cindex @samp{Malformed dumpdir: 'X' never used}, warning message
+@item bad-dumpdir
+@samp{Malformed dumpdir: 'X' never used}
+@end table
+
@node interactive
@section Asking for Confirmation During Operations
@cindex Interactive operation
@node Operations
@subsection The Five Advanced @command{tar} Operations
-@UNREVISED
+@cindex basic operations
In the last chapter, you learned about the first three operations to
@command{tar}. This chapter presents the remaining five operations to
@command{tar}: @option{--append}, @option{--update}, @option{--concatenate},
@node append
@subsection How to Add Files to Existing Archives: @option{--append}
-@UNREVISED
+@cindex appending files to existing archive
@opindex append
If you want to add files to an existing archive, you don't need to
create a new archive; you can use @option{--append} (@option{-r}).
member will end up being extracted, as it will replace the one
extracted before it, and so on.
+@cindex extracting @var{n}th copy of the file
+@xopindex{occurrence, described}
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
@cindex Members, replacing with other members
@cindex Replacing members with other members
+@xopindex{delete, using before --append}
If you want to replace an archive member, use @option{--delete} to
-delete the member you want to remove from the archive, , and then use
+delete the member you want to remove from the archive, and then use
@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
@node appending files
@subsubsection Appending Files to an Archive
-@UNREVISED
@cindex Adding files to an Archive
@cindex Appending files to an Archive
@cindex Archives, Appending files to
+@opindex append
The simplest way to add a file to an already existing archive is the
@option{--append} (@option{-r}) operation, which writes specified
@node multiple
@subsubsection Multiple Members with the Same Name
+@cindex members, multiple
+@cindex multiple members
You can use @option{--append} (@option{-r}) to add copies of files
which have been updated since the archive was created. (However, we
@node update
@subsection Updating an Archive
-@UNREVISED
@cindex Updating an archive
-
@opindex update
+
In the previous section, you learned how to use @option{--append} to
add a file to an existing archive. A related operation is
@option{--update} (@option{-u}). The @option{--update} operation
@node how to update
@subsubsection How to Update an Archive Using @option{--update}
+@opindex update
You must use file name arguments with the @option{--update}
(@option{-u}) operation. If you don't specify any files,
@node delete
@subsection Removing Archive Members Using @option{--delete}
-@UNREVISED
@cindex Deleting files from an archive
@cindex Removing files from an archive
@node compare
@subsection Comparing Archive Members with the File System
@cindex Verifying the currency of an archive
-@UNREVISED
@opindex compare
The @option{--compare} (@option{-d}), or @option{--diff} operation compares
@node extract options
@section Options Used by @option{--extract}
-@UNREVISED
+@cindex options for use with @option{--extract}
@xopindex{extract, additional options}
The previous chapter showed how to use @option{--extract} to extract
@node Reading
@subsection Options to Help Read Archives
@cindex Options when reading archives
-@UNREVISED
@cindex Reading incomplete records
@cindex Records, incomplete
@vrindex TAR_ATIME, to-command environment
@item TAR_ATIME
Time of last access. It is a decimal number, representing seconds
-since the epoch. If the archive provides times with nanosecond
+since the Epoch. If the archive provides times with nanosecond
precision, the nanoseconds are appended to the timestamp after a
decimal point.
GID of the file owner.
@end table
-In addition to these variables, @env{TAR_VERSION} contains the
+Additionally, the following variables contain information about
+tar mode and the archive being processed:
+
+@table @env
+@vrindex TAR_VERSION, to-command environment
+@item TAR_VERSION
@GNUTAR{} version number.
+@vrindex TAR_ARCHIVE, to-command environment
+@item TAR_ARCHIVE
+The name of the archive @command{tar} is processing.
+
+@vrindex TAR_BLOCKING_FACTOR, to-command environment
+@item TAR_BLOCKING_FACTOR
+Current blocking factor (@pxref{Blocking}.
+
+@vrindex TAR_VOLUME, to-command environment
+@item TAR_VOLUME
+Ordinal number of the volume @command{tar} is processing.
+
+@vrindex TAR_FORMAT, to-command environment
+@item TAR_FORMAT
+Format of the archive being processed. @xref{Formats}, for a complete
+list of archive format names.
+@end table
+
If @var{command} exits with a non-0 status, @command{tar} will print
an error message similar to the following:
@node Backups
@chapter Performing Backups and Restoring Files
-@UNREVISED
+@cindex backups
-@GNUTAR{} is distributed along with the scripts
-which the Free Software Foundation uses for performing backups. There
-is no corresponding scripts available yet for doing restoration of
-files. Even if there is a good chance those scripts may be satisfying
-to you, they are not the only scripts or methods available for doing
+@GNUTAR{} is distributed along with the scripts for performing backups
+and restores. Even if there is a good chance those scripts may be
+satisfying to you, they are not the only scripts or methods available for doing
backups and restore. You may well create your own, or use more
sophisticated packages dedicated to that purpose.
Some users are enthusiastic about @code{Amanda} (The Advanced Maryland
Automatic Network Disk Archiver), a backup system developed by James
da Silva @file{jds@@cs.umd.edu} and available on many Unix systems.
-This is free software, and it is available at these places:
-
-@smallexample
-http://www.cs.umd.edu/projects/amanda/amanda.html
-ftp://ftp.cs.umd.edu/pub/amanda
-@end smallexample
+This is free software, and it is available from @uref{http://www.amanda.org}.
@FIXME{
backups: @option{--listed-incremental=@var{snapshot-file}} (@option{-g
@var{snapshot-file}}) and @option{--incremental} (@option{-G}).
-@opindex listed-incremental
+@xopindex{listed-incremental, described}
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
/usr}
@end smallexample
+@anchor{--level=0}
+@xopindex{level, described}
+You can force @samp{level 0} backups either by removing the snapshot
+file before running @command{tar}, or by supplying the
+@option{--level=0} option, e.g.:
+
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar-0 \
+ --level=0 \
+ /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 @option{--atime-preserve=replace} option), or if you set the clock
@node Choosing
@chapter Choosing Files and Names for @command{tar}
-@UNREVISED
Certain options to @command{tar} enable you to specify a name for your
archive. Other options let you decide which files to include or exclude
@node file
@section Choosing and Naming Archive Files
-@UNREVISED
@cindex Naming an archive
@cindex Archive Name
@cindex Choosing an archive file
@cindex Where is the archive?
+@opindex file
By default, @command{tar} uses an archive file name that was compiled when
it was built on the system; usually this name refers to some physical
tape drive on the machine. However, the person who installed @command{tar}
@cindex Reading file names from a file
@cindex Lists of file names
@cindex File Name arguments, alternatives
+@cindex @command{find}, using with @command{tar}
Instead of giving the names of files or archive members on the command
line, you can put the names into a file, and then use the
@option{--files-from=@var{file-of-names}} (@option{-T
@node exclude
@section Excluding Some Files
-@UNREVISED
@cindex File names, excluding files by
@cindex Excluding files by name and pattern
@cindex Excluding files by file system
+@opindex exclude
+@opindex exclude-from
To avoid operating on files whose names match a particular pattern,
use the @option{--exclude} or @option{--exclude-from} options.
However, empty lines are OK.
+@table @option
@cindex version control system, excluding files
@cindex VCS, excluding files
@cindex SCCS, excluding files
@cindex Arch, excluding files
@cindex Mercurial, excluding files
@cindex Darcs, excluding files
-@table @option
@opindex exclude-vcs
@item --exclude-vcs
Exclude files and directories used by following version control
systems: @samp{CVS}, @samp{RCS}, @samp{SCCS}, @samp{SVN}, @samp{Arch},
@samp{Bazaar}, @samp{Mercurial}, and @samp{Darcs}.
-@end table
As of version @value{VERSION}, the following files are excluded:
@item @file{_darcs}
@end itemize
+@opindex exclude-backups
+@item --exclude-backups
+Exclude backup and lock files. This option causes exclusion of files
+that match the following shell globbing patterns:
+
+@table @asis
+@item .#*
+@item *~
+@item #*#
+@end table
+
+@end table
+
@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
@node after
@section Operating Only on New Files
-@UNREVISED
@cindex Excluding file by age
@cindex Data Modification time, excluding files by
modification of the file's data (rather than status
changes), then use the @option{--newer-mtime=@var{date}} option.
+@cindex --after-date and --update compared
+@cindex --newer-mtime and --update compared
You may use these options with any operation. Note that these options
differ from the @option{--update} (@option{-u}) operation in that they
allow you to specify a particular date against which @command{tar} can
@node recurse
@section Descending into Directories
-@UNREVISED
@cindex Avoiding recursion in directories
@cindex Descending directories, avoiding
@cindex Directories, avoiding recursion
@cindex Recursion in directories, avoiding
-@FIXME{arrggh! this is still somewhat confusing to me. :-< }
-
Usually, @command{tar} will recursively explore all directories (either
those given on the command line or through the @option{--files-from}
option) for the various files they contain. However, you may not always
want @command{tar} to act this way.
@opindex no-recursion
+@cindex @command{find}, using with @command{tar}
The @option{--no-recursion} option inhibits @command{tar}'s recursive descent
into specified directories. If you specify @option{--no-recursion}, you can
-use the @command{find} utility for hunting through levels of directories to
+use the @command{find} (@pxref{Top,, find, find, GNU Find Manual})
+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.
+@command{tar}.
@table @option
@item --no-recursion
@node one
@section Crossing File System Boundaries
@cindex File system boundaries, not crossing
-@UNREVISED
@command{tar} will normally automatically cross file system boundaries in
order to archive files which are part of a directory tree. You can
@node absolute
@subsection Absolute File Names
-@UNREVISED
+@cindex absolute file names
+@cindex file names, absolute
+
+By default, @GNUTAR{} drops a leading @samp{/} on
+input or output, and complains about file names containing a @file{..}
+component. There is an option that turns off this behavior:
@table @option
@opindex absolute-names
containing a @file{..} file name component.
@end table
-By default, @GNUTAR{} drops a leading @samp{/} on
-input or output, and complains about file names containing a @file{..}
-component. This option turns off this behavior.
-
When @command{tar} extracts archive members from an archive, it strips any
leading slashes (@samp{/}) from the member name. This causes absolute
member names in the archive to be treated as relative file names. This
@FIXME{Should be an example in the tutorial/wizardry section using this
to transfer files between systems.}
-@FIXME{Is write access an issue?}
-
@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
@end table
-@FIXME{this is still horrible; need to talk with dan on monday.}
-
@command{tar} prints out a message about removing the @samp{/} from
file names. This message appears once per @GNUTAR{}
invocation. It represents something which ought to be told; ignoring
@cindex gzip
@cindex bzip2
+@cindex lzip
@cindex lzma
@cindex lzop
@cindex compress
@GNUTAR{} is able to create and read compressed archives. It supports
-@command{gzip}, @command{bzip2}, @command{lzma} and @command{lzop} compression
-programs. For backward compatibility, it also supports
-@command{compress} command, although we strongly recommend against
-using it, because it is by far less effective than other compression
-programs@footnote{It also had patent problems in the past.}.
+@command{gzip}, @command{bzip2}, @command{lzip}, @command{lzma} and
+@command{lzop} compression programs. For backward compatibility, it
+also supports @command{compress} command, although we strongly recommend
+against using it, because it is by far less effective than other
+compression programs@footnote{It also had patent problems in the past.}.
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,
+@option{--lzip} to create an @asis{lzip} compressed archive,
@option{-J} (@option{--xz}) to create an @asis{XZ} archive,
@option{--lzma} to create an @asis{LZMA} compressed
archive, @option{--lzop} to create an @asis{LSOP} archive, and
@item @samp{.tz2} @tab @command{bzip2}
@item @samp{.tbz2} @tab @command{bzip2}
@item @samp{.tbz} @tab @command{bzip2}
+@item @samp{.lz} @tab @command{lzip}
@item @samp{.lzma} @tab @command{lzma}
@item @samp{.tlz} @tab @command{lzma}
@item @samp{.lzo} @tab @command{lzop}
@itemx --bzip2
Filter the archive through @code{bzip2}. Otherwise like @option{--gzip}.
+@opindex lzip
+@item --lzip
+Filter the archive through @command{lzip}. Otherwise like @option{--gzip}.
+
@opindex lzma
@item --lzma
Filter the archive through @command{lzma}. Otherwise like @option{--gzip}.
@node Attributes
@section Handling File Attributes
-@UNREVISED
+@cindex atrributes, files
+@cindex file attributes
When @command{tar} reads files, it updates their access times. To
avoid this, use the @option{--atime-preserve[=METHOD]} option, which can either
reset the access time retroactively or avoid changing it in the first
place.
-Handling of file attributes
-
@table @option
@opindex atime-preserve
@item --atime-preserve
@node hard links
@subsection Hard Links
-@UNREVISED{}
@cindex File names, using hard links
@cindex hard links, dereferencing
@cindex dereferencing hard links
%d/PaxHeaders.%p/%f
@end smallexample
+@item exthdr.mtime=@var{value}
+
+This keyword defines the value of the @samp{mtime} field that
+is written into the ustar header blocks for the extended headers.
+By default, the @samp{mtime} field is set to the modification time
+of the archive member described by that extended headers.
+
@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
environment variable. If @var{TMPDIR} is not set, @command{tar}
uses @samp{/tmp}.
+@item exthdr.mtime=@var{value}
+
+This keyword defines the value of the @samp{mtime} field that
+is written into the ustar header blocks for the global extended headers.
+By default, the @samp{mtime} field is set to the time when
+@command{tar} was invoked.
+
@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
stored in the archive.
@end table
+In any of the forms described above, the @var{value} may be
+a string enclosed in curly braces. In that case, the string
+between the braces is understood either as a textual time
+representation, as described in @ref{Date input formats}, or a name of
+the existing file, starting with @samp{/} or @samp{.}. In the latter
+case, the modification time of that file is used.
+
+For example, to set all modification times to the current date, you
+use the following option:
+
+@smallexample
+--pax-option='mtime:=@{now@}'
+@end smallexample
+
+Note quoting of the option's argument.
+
+@cindex archives, binary equivalent
+@cindex binary equivalent archives, creating
+As another example, here is the option that ensures that any two
+archives created using it, will be binary equivalent if they have the
+same contents:
+
+@smallexample
+--pax-option=exthdr.name=%d/PaxHeaders/%f,atime:=0
+@end smallexample
+
@node Checksumming
@subsection Checksumming Problems
@cindex large values
@cindex future time stamps
@cindex negative time stamps
-@UNREVISED{}
+@UNREVISED
The above sections suggest to use @samp{oldest possible} archive
format if in doubt. However, sometimes it is not possible. If you
@node Blocking
@section Blocking
-@UNREVISED
+@cindex block
+@cindex record
@dfn{Block} and @dfn{record} terminology is rather confused, and it
is also confusing to the expert reader. On the other hand, readers
@end table
-@FIXME{Is there a better way to frob the spacing on the list?}
-
If you don't specify a @var{tapename}, @command{mt} uses the environment
variable @env{TAPE}; if @env{TAPE} is not set, @command{mt} will use
the default device specified in your @file{sys/mtio.h} file
@node Tape Files
@subsection Tape Files
+@cindex labeling archives
+@opindex label
@UNREVISED
To give the archive a name which will be recorded in it, use the
distribution tarballs. @xref{Formats,v7}, for the detailed discussion
of this issue and its implications.
-@FIXME{Change the first argument to tar-formats when the new Automake is
-out. The proposition to add @anchor{} to the appropriate place of its
-docs was accepted by Automake people --Sergey 2006-05-25}.
-@xref{Options, tar-v7, Changing Automake's Behavior,
+@xref{Options, tar-formats, Changing Automake's Behavior,
automake, GNU Automake}, for a description on how to use various
archive formats with @command{automake}.
projects / chaz / tar / blobdiff