@titlepage
@title @acronym{GNU} tar: an archiver tool
@subtitle @value{RENDITION} @value{VERSION}, @value{UPDATED}
-@author Melissa Weisshaus, Jay Fenlason,
-@author Thomas Bushnell, n/BSG, Amy Gorin
-@c he said to remove it: Fran@,{c}ois Pinard
-@c i'm thinking about how the author page *should* look. -mew 2may96
+@author John Gilmore, Jay Fenlason et al.
@page
@vskip 0pt plus 1filll
Appendices
* Genfile::
+* Snapshot Files::
* Free Software Needs Free Documentation::
* Copying This Manual::
* Index::
* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
Performing Backups and Restoring Files
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
Reading Names from a File
* controlling pattern-patching with exclude::
* problems with exclude::
-Crossing Filesystem Boundaries
+Crossing File System Boundaries
* directory:: Changing Directory
* absolute:: Absolute File Names
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
-GNU tar test suite
+GNU tar internals and development
* Genfile::
+* Snapshot Files::
Copying This Manual
archives. An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth. (In addition, archives record access
-permissions, user and group, size in bytes, and last modification time.
+permissions, user and group, size in bytes, and data modification time.
Some archives also record the file names in each archived directory, as
well as other file and directory information.) You can use @command{tar}
to @dfn{create} a new archive in a specified directory.
manual, we use the term @dfn{file} to refer only to files accessible in
the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive. Similarly, a
-@dfn{file name} is the name of a file, as it resides in the filesystem,
+@dfn{file name} is the name of a file, as it resides in the file system,
and a @dfn{member name} is the name of an archive member within the
archive.
@cindex extraction
@cindex unpacking
The term @dfn{extraction} refers to the process of copying an archive
-member (or multiple members) into a file in the filesystem. Extracting
+member (or multiple members) into a file in the file system. Extracting
all the members of an archive is often called @dfn{extracting the
archive}. The term @dfn{unpack} can also be used to refer to the
extraction of many or all the members of an archive. Extracting an
accidental destruction of the information in those files.
@GNUTAR{} has special features that allow it to be
used to make incremental and full dumps of all the files in a
-filesystem.
+file system.
@item Transportation
You can create an archive on one system, transfer it to another system,
@end itemize
Some of these aims are already attained, while others are still
-being worked upon. From the point of view of an end user, the
+being worked upon. From the point of view of an end user, the
following issues need special mentioning:
@table @asis
option as a synonym for @option{--old-archive}.
@GNUTAR{} starting from version 1.13.90 understands this option as
-a synonym for @option{--no-same-owner}. This is compatible with
+a synonym for @option{--no-same-owner}. This is compatible with
UNIX98 @command{tar} implementations.
However, to facilitate transition, @option{-o} option retains its
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
+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
@item Use of short option @option{-l}
Earlier versions of @GNUTAR{} understood @option{-l} option as a
-synonym for @option{--one-file-system}. Such usage is deprecated.
+synonym for @option{--one-file-system}. Such usage is deprecated.
For compatibility with other implementations future versions of
@GNUTAR{} will understand this option as a synonym for
@option{--check-links}.
@item Use of options @option{--portability} and @option{--old-archive}
-These options are deprecated. Please use @option{--format=v7} instead.
+These options are deprecated. Please use @option{--format=v7} instead.
@item Use of option @option{--posix}
-This option is deprecated. Please use @option{--format=posix} instead.
+This option is deprecated. Please use @option{--format=posix} instead.
@end table
@node Authors
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
+again. Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
Poznyakoff and Jeff Bailey.
Support for @acronym{POSIX} archives was added by Sergey Poznyakoff.
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
+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}.
use some basic utilities. For example, you should know how to create,
list, copy, rename, edit, and delete files and directories; how to
change between directories; and how to figure out where you are in the
-filesystem. You should have some basic understanding of directory
+file system. You should have some basic understanding of directory
structure and how files are named according to which directory they are
in. You should understand concepts such as standard output and standard
input, what various definitions of the term ``argument'' mean, and the
this chapter will cover how to use these operations in detail. We will
present the rest of the operations in the next chapter.
-@table @kbd
+@table @option
@item --create
@itemx -c
Create a new @command{tar} archive.
@node file tutorial
@unnumberedsubsec The @option{--file} Option
-@table @kbd
+@table @option
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Specify the name of an archive file.
@node verbose tutorial
@unnumberedsubsec The @option{--verbose} Option
-@table @kbd
+@table @option
@item --verbose
@itemx -v
Show the files being worked on as @command{tar} is running.
Sometimes, a single instance of @option{--verbose} on the command line
will show a full, @samp{ls} style listing of an archive or files,
-@c FIXME: Describe the exact output format, e.g., how hard links are displayed.
-giving sizes, owners, and similar information. Other times,
-@option{--verbose} will only show files or members that the particular
+giving sizes, owners, and similar information. @FIXME{Describe the
+exact output format, e.g., how hard links are displayed.}
+Other times, @option{--verbose} will only show files or members that the particular
operation is operating on at the time. In the latter case, you can
use @option{--verbose} twice in a command to get a listing such as that
in the former case. For example, instead of saying
@node help tutorial
@unnumberedsubsec Getting Help: Using the @option{--help} Option
-@table @kbd
+@table @option
@item --help
The @option{--help} option to @command{tar} prints out a very brief list of
@command{tar}, to avoid errors).
Note that the part of the command which says,
-@w{@kbd{--file=collection.tar}} is considered to be @emph{one} argument.
+@w{@option{--file=collection.tar}} is considered to be @emph{one} argument.
If you substituted any other string of characters for
@kbd{collection.tar}, then that string would become the name of the
archive file you create.
want placed in the archive. If you do not specify any archive
members, @GNUTAR{} will complain.
-If you now list the contents of the working directory (@kbd{ls}), you will
+If you now list the contents of the working directory (@command{ls}), you will
find the archive file listed as well as the files you saw previously:
@smallexample
@noindent
This will put you into the directory which contains @file{practice},
-i.e. your home directory. Once in the superior directory, you can
+i.e., your home directory. Once in the superior directory, you can
specify the subdirectory, @file{practice}, as a file name argument. To
store @file{practice} in the new archive file @file{music.tar}, type:
-rw-rw-rw- myself user 62 1990-05-23 10:55 folk
@end smallexample
+@cindex listing member and file names
+@anchor{listing member and file names}
+It is important to notice that the output of @kbd{tar --list
+--verbose} does not necessarily match that produced by @kbd{tar
+--create --verbose} while creating the archive. It is because
+@GNUTAR{}, unless told explicitly not to do so, removes some directory
+prefixes from file names before storing them in the archive
+(@xref{absolute}, for more information). In other
+words, in verbose mode @GNUTAR{} shows @dfn{file names} when creating
+an archive and @dfn{member names} when listing it. Consider this
+example:
+
+@smallexample
+@group
+$ @kbd{tar cfv archive /etc/mail}
+tar: Removing leading `/' from member names
+/etc/mail/
+/etc/mail/sendmail.cf
+/etc/mail/aliases
+$ @kbd{tar tf archive}
+etc/mail/
+etc/mail/sendmail.cf
+etc/mail/aliases
+@end group
+@end smallexample
+
+@cindex @option{--show-stored-names} described
+ This default behavior can sometimes be inconvenient. You can force
+@GNUTAR{} show member names when creating archive by supplying
+@option{--show-stored-names} option.
+
+@table @option
+@item --show-stored-names
+Print member (not @emph{file}) names when creating the archive.
+@end table
+
@cindex File name arguments, using @option{--list} with
@cindex @option{--list} with file name arguments
You can specify one or more individual member names as arguments when
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{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}.
+writing, atime and ctime are not restored. Since this is a tutorial
+for a beginning user, it should hardly be mentioned here. Maybe in
+a footnote? --gray}.
First, make sure you are in the @file{practice} directory, and list the
files in the directory. Now, delete the file, @samp{blues}, and list
@noindent
If you list the files in the directory again, you will see that the file
-@file{blues} has been restored, with its original permissions, creation
+@file{blues} has been restored, with its original permissions, data modification
times, and owner.@FIXME{This is only accidentally true, but not in
general. In most cases, one has to be root for restoring the owner, and
use a special option for restoring permissions. Here, it just happens
If you give the name of a directory as either a file name or a member
name, then @command{tar} acts recursively on all the files and directories
beneath that directory. For example, the name @file{/} identifies all
-the files in the filesystem to @command{tar}.
+the files in the file system to @command{tar}.
The distinction between file names and archive member names is especially
important when shell globbing is used, and sometimes a source of confusion
styles.
@FIXME{menu at end of this node. need to think of an actual outline
-for this chapter; probably do that after stuff from chap. 4 is
+for this chapter; probably do that after stuff from chapter 4 is
incorporated.}
@node Styles
only use the option style(s) which makes the most sense to you until you
feel comfortable with the others.
-Some options @emph{may} take an argument (currently, there are
-two such options: @value{op-backup} and @value{op-occurrence}). Such
+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,
+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" with "long", or *ugh* vice versa.}
Each option has at least one long (or mnemonic) name starting with two
-dashes in a row, e.g.@: @option{--list}. The long names are more clear than
+dashes in a row, e.g., @option{--list}. The long names are more clear than
their corresponding short or old names. It sometimes happens that a
single mnemonic option has many different different names which are
synonymous, such as @option{--compare} and @option{--diff}. In addition,
for those not fully acquainted with @command{tar}.
Mnemonic 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
+immediately following the option name. There are two ways of
+specifying a mandatory argument. It can be separated from the
option name either by an equal sign, or by any amount of
-white space characters. For example, the @option{--file} option (which
+white space characters. For example, the @option{--file} option (which
tells the name of the @command{tar} archive) is given a file such as
@file{archive.tar} as argument by using any of the following notations:
@option{--file=archive.tar} or @option{--file archive.tar}.
In contrast, optional arguments must always be introduced using
-an equal sign. For example, the @option{--backup} option takes
-an optional argument specifying backup type. It must be used
+an equal sign. For example, the @option{--backup} option takes
+an optional argument specifying backup type. It must be used
as @option{--backup=@var{backup-type}}.
@node Short Options
@subsection Short Option Style
Most options also have a short option name. Short options start with
-a single dash, and are followed by a single character, e.g.@: @option{-t}
+a single dash, and are followed by a single character, e.g., @option{-t}
(which is equivalent to @option{--list}). The forms are absolutely
identical in function; they are interchangeable.
Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When
short options are clumped as a set, use one (single) dash for them
-all, e.g.@: @w{@samp{@command{tar} -cvf}}. Only the last option in
+all, e.g., @w{@samp{@command{tar} -cvf}}. Only the last option in
such a set is allowed to have an argument@footnote{Clustering many
options, the last of which has an argument, is a rather opaque way to
write options. Some wonder if @acronym{GNU} @code{getopt} should not
@node Operation Summary
@subsection Operations
-@table @kbd
+@table @option
@item --append
@itemx -r
@item --get
@itemx -x
-Same as @option{--extract}. @xref{extract}.
+Same as @option{--extract}. @xref{extract}.
@item --list
@itemx -t
@node Option Summary
@subsection @command{tar} Options
-@table @kbd
+@table @option
@item --absolute-names
@itemx -P
Normally when creating an archive, @command{tar} strips an initial
@samp{/} from member names. This option disables that behavior.
-@FIXME-xref{}
+@xref{absolute}.
@item --after-date
@FIXME-xref{}
@item --atime-preserve
-
-Tells @command{tar} to preserve the access time field in a file's inode when
-reading it. Due to limitations in the @code{utimes} system call, the
-modification time field is also preserved, which may cause problems if
-the file is simultaneously being modified by another program.
-This option is incompatible with incremental backups, because
-preserving the access time involves updating the last-changed time.
-Also, this option does not work on files that you do not own,
-unless you're root.
-@FIXME-xref{}
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+
+Attempt to preserve the access time of files when reading them. This
+option currently is effective only on files that you own, unless you
+have superuser privileges.
+
+Though this option should work on recent Linux kernel versions, it is
+not reliable on other platforms. To preserve the access time reliably
+on those platforms, you can mount the file system read-only, or access
+the file system via a read-only loopback mount, or use the
+@samp{noatime} mount option available on some systems. However,
+mounting typically requires superuser privileges and can be a pain to
+manage, so the @option{--atime-preserve} option can be useful despite
+its glitches on other platforms.
+
+@value{op-atime-preserve-replace} remembers the access time of a file
+before reading it, and then restores the access time afterwards. This
+may cause problems if other programs are reading the file at the same
+time, as the times of their accesses will be lost. On most platforms
+restoring the access time also requires @command{tar} to restore the
+data modification time too, so this option may also cause problems if
+other programs are writing the file at the same time. (Tar attempts
+to detect this situation, but cannot do so reliably due to race
+conditions.) Worse, on most platforms restoring the access time also
+updates the status change time, which means that this option is
+incompatible with incremental backups.
+
+@value{op-atime-preserve-system} avoids changing time stamps on files
+other than directories, without interfering with time stamp updates
+caused by other programs, so it works better with incremental backups.
+However, it requires a special @code{O_NOATIME} option from the
+underlying operating and file system implementation, and it requires
+that searching directories does not update their access times. As of
+this writing (November 2005) this works only in a few new Linux
+kernels. Worse, there is currently no reliable way to know whether
+the features actually work. Sometimes @command{tar} knows for sure
+that the features are not working, so it will complain and exit right
+away if you try to use @value{op-atime-preserve-system}; but other
+times @command{tar} might think that the option is supported when it
+is not actually working.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@value{op-atime-preserve-replace}, but this may change in the future
+as support for @value{op-atime-preserve-system} improves.
@item --backup=@var{backup-type}
@item --check-links
@itemx -l
If this option was given, @command{tar} will check the number of links
-dumped for each processed file. If this number does not match the
+dumped for each processed file. If this number does not match the
total number of hard links for the file, a warning message will be
output.
Future versions will take @option{-l} as a short version of
-@option{--check-links}. However, current release still retains the old
+@option{--check-links}. However, current release still retains the old
semantics for @option{-l}.
@xref{Current status}, for more information.
@item --format=@var{format}
-Selects output archive format. @var{Format} may be one of the
+Selects output archive format. @var{Format} may be one of the
following:
@table @samp
1.12 or earlier.
@item gnu
-Creates archive in GNU tar 1.13 format. Basically it is the same as
+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.
Used to inform @command{tar} that it is working with an old
@acronym{GNU}-format incremental backup archive. It is intended
-primarily for backwards compatibility only. @FIXME-xref{}
+primarily for backwards compatibility only. @FIXME{incremental and
+listed-incremental}.
@item --index-file=@var{file}
@command{tar} creates is a new @acronym{GNU}-format incremental
backup, using @var{snapshot-file} to determine which files to backup.
With other operations, informs @command{tar} that the archive is in
-incremental format. @FIXME-xref{}
+incremental format. @FIXME{incremental and listed-incremental}.
@item --mode=@var{permissions}
@itemx --seek
Assume that the archive media supports seeks to arbitrary
-locations. Usually @command{tar} determines automatically whether
-the archive can be seeked or not. This option is intended for use
+locations. Usually @command{tar} determines automatically whether
+the archive can be seeked or not. This option is intended for use
in cases when such recognition fails.
@item --newer=@var{date}
When creating an archive, @command{tar} will only add files that have changed
since @var{date}. If @var{date} begins with @samp{/} or @samp{.}, it
-is taken to be the name of a file whose last-modified time specifies
+is taken to be the name of a file whose data modification time specifies
the date. @FIXME-xref{}
@item --newer-mtime=@var{date}
@item --null
When @command{tar} is using the @option{--files-from} option, this option
-instructs @command{tar} to expect filenames terminated with @kbd{NUL}, so
+instructs @command{tar} to expect filenames terminated with @option{NUL}, so
@command{tar} can correctly work with file names that contain newlines.
@FIXME-xref{}
@item -o
When extracting files, this option is a synonym for
-@option{--no-same-owner}, i.e. it prevents @command{tar} from
+@option{--no-same-owner}, i.e. it prevents @command{tar} from
restoring ownership of files being extracted.
When creating an archive, @option{-o} is a synonym for
-@option{--old-archive}. This behavior is for compatibility
+@option{--old-archive}. This behavior is for compatibility
with previous versions of @GNUTAR{}, and will be
removed in the future releases.
line or via @option{-T} option.
This option instructs @command{tar} to process only the @var{number}th
-occurrence of each named file. @var{Number} defaults to 1, so
+occurrence of each named file. @var{Number} defaults to 1, so
@smallexample
tar -x -f archive.tar --occurrence filename
directory.
Earlier versions of @GNUTAR{} understood @option{-l} as a
-synonym for @option{--one-file-system}. Although such usage is still
+synonym for @option{--one-file-system}. Although such usage is still
allowed in the present version, it is @emph{strongly discouraged}.
The future versions of @GNUTAR{} will use @option{-l} as
a synonym for @option{--check-links}.
@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
+(@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:
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
+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:
+man 7 glob}. For example:
@smallexample
--pax-option delete=security.*
@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
+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
+@headitem Meta-character @tab Replaced By
@item %d @tab The directory name of the file, equivalent to the
result of the @command{dirname} utility on the translated pathname.
@item %f @tab The filename of the file, equivalent to the result
@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
+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
+@headitem Meta-character @tab Replaced By
@item %n @tab An integer that represents the
sequence number of the global extended header record in the archive,
starting at 1.
@noindent
where @samp{$TMPDIR} represents the value of the @var{TMPDIR}
-environment variable. If @var{TMPDIR} is not set, @command{tar}
+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,
+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}
+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
@item --show-defaults
Displays the default options used by @command{tar} and exits
-successfully. This option is intended for use in shell scripts.
+successfully. This option is intended for use in shell scripts.
Here is an example of what you can see using this option:
@smallexample
Instructs @command{tar} to mention directories its skipping over when
operating on a @command{tar} archive. @FIXME-xref{}
+@item --show-stored-names
+
+This option has effect only when used in conjunction with one of
+archive creation operations. It instructs tar to list the member names
+stored in the archive, as opposed to the actual file
+names. @xref{listing member and file names}.
+
@item --sparse
@itemx -S
Specifies the length of tapes that @command{tar} is writing as being
@w{@var{num} x 1024} bytes long. @FIXME-xref{}
+@item --test-label
+
+Reads the volume label. If an argument is specified, test whether it
+matches the volume label. @xref{--test-label option}.
+
@item --to-stdout
@itemx -O
@item --touch
@itemx -m
-Sets the modification time of extracted files to the extraction time,
-rather than the modification time stored in the archive.
+Sets the data modification time of extracted files to the extraction time,
+rather than the data modification time stored in the archive.
@xref{Writing}.
@item --uncompress
@item --utc
-Display file modification dates in @acronym{UTC}. This option implies
+Display file modification dates in @acronym{UTC}. This option implies
@option{--verbose}.
@item --verbose
Here is an alphabetized list of all of the short option forms, matching
them with the equivalent long option.
-@table @kbd
+@table @option
@item -A
@item -l
-@option{--one-file-system}. Use of this short option is deprecated. It
+@option{--one-file-system}. Use of this short option is deprecated. It
is retained for compatibility with the earlier versions of GNU
@command{tar}, and will be changed in future releases.
When creating --- @option{--no-same-owner}, when extracting ---
@option{--portability}.
-The later usage is deprecated. It is retained for compatibility with
-the earlier versions of @GNUTAR{}. In the future releases
+The later usage is deprecated. It is retained for compatibility with
+the earlier versions of @GNUTAR{}. In the future releases
@option{-o} will be equivalent to @option{--no-same-owner} only.
@item -p
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 prints
-a message each 10 records read or written. 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.
The five operations that we will cover in this chapter are:
-@table @kbd
+@table @option
@item --append
@itemx -r
Add new entries to an archive that already exists.
with the same name. Some operations treat these same-named members no
differently than any other set of archive members: for example, if you
view an archive with @value{op-list}, you will see all of those members
-listed, with their modification times, owners, etc.
+listed, with their data modification times, owners, etc.
Other operations don't deal with these members as perfectly as you might
prefer; if you were to use @value{op-extract} to extract the archive,
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
+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
@end smallexample
@noindent
-would extract only the second copy. @xref{Option Summary,---occurrence}, for the description of @value{op-occurrence} option.
+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...
Both @option{--update} and @option{--append} work by adding to the end
of the archive. When you extract a file from the archive, only the
version stored last will wind up in the file system, unless you use
-the @value{op-backup} option. @FIXME-ref{Multiple Members with the
+the @value{op-backup} option. @FIXME-ref{Multiple Members with the
Same Name}
@menu
already exist and must have been created using compatible format
parameters. @FIXME-pxref{Matching Format Parameters}The new,
concatenated archive will be called by the same name as the first
-archive listed on the command line. @FIXME{is there a way to specify a
+archive listed on the command line. @FIXME{is there a way to specify a
new name?}
Like @value{op-append}, this operation cannot be performed on some
@node Ignore Failed Read
@subsection Ignore Fail Read
-@table @kbd
+@table @option
@item --ignore-failed-read
Do not exit with nonzero on unreadable files or directories.
@end table
there's a better way of organizing them.}
The previous chapter showed how to use @value{op-extract} to extract
-an archive into the filesystem. Various options cause @command{tar} to
+an archive into the file system. Various options cause @command{tar} to
extract more information than just file contents, such as the owner,
the permissions, the modification date, and so forth. This section
presents options to be used with @option{--extract} when certain special
@FIXME{need sentence or so of intro here}
-@table @kbd
+@table @option
@item --read-full-records
@item -B
Use in conjunction with @value{op-extract} to read an archive which
Normally, @command{tar} stops reading when it encounters a block of zeros
between file entries (which usually indicates the end of the archive).
@value{op-ignore-zeros} allows @command{tar} to completely read an archive
-which contains a block of zeros before the end (i.e.@: a damaged
-archive, or one which was created by concatenating several archives
+which contains a block of zeros before the end (i.e., a damaged
+archive, or one that was created by concatenating several archives
together).
The @value{op-ignore-zeros} option is turned off by default because many
does not write after the end of an archive, but seeks to
maintain compatiblity among archiving utilities.
-@table @kbd
+@table @option
@item --ignore-zeros
@itemx -i
-To ignore blocks of zeros (ie.@: end-of-archive entries) which may be
+To ignore blocks of zeros (i.e., end-of-archive entries) which may be
encountered while reading an archive. Use in conjunction with
@value{op-extract} or @value{op-list}.
@end table
@subsection Changing How @command{tar} Writes Files
@cindex Overwriting old files, prevention
@cindex Protecting old files
+@cindex Data modification times of extracted files
@cindex Modification times of extracted files
@cindex Permissions of extracted files
@cindex Modes of extracted files
* Keep Newer Files::
* Unlink First::
* Recursive Unlink::
-* Modification Times::
+* Data Modification Times::
* Setting Access Permissions::
* Writing to Standard Output::
* remove files::
Some people argue that @GNUTAR{} should not hesitate
to overwrite files with other files when extracting. When extracting
a @command{tar} archive, they expect to see a faithful copy of the
-state of the filesystem when the archive was created. It is debatable
+state of the file system when the archive was created. It is debatable
that this would always be a proper behavior. For example, suppose one
has an archive in which @file{usr/local} is a link to
@file{usr/local2}. Since then, maybe the site removed the link and
@node Overwrite Old Files
@unnumberedsubsubsec Overwrite Old Files
-@table @kbd
+@table @option
@item --overwrite
Overwrite existing files and directory metadata when extracting files
from an archive.
@node Keep Old Files
@unnumberedsubsubsec Keep Old Files
-@table @kbd
+@table @option
@item --keep-old-files
@itemx -k
Do not replace existing files from archive. The
@node Keep Newer Files
@unnumberedsubsubsec Keep Newer Files
-@table @kbd
+@table @option
@item --keep-newer-files
Do not replace existing files that are newer than their archive
-copies. This option is meaningless with @value{op-list}.
+copies. This option is meaningless with @value{op-list}.
@end table
@node Unlink First
@unnumberedsubsubsec Unlink First
-@table @kbd
+@table @option
@item --unlink-first
@itemx -U
Remove files before extracting over them.
@node Recursive Unlink
@unnumberedsubsubsec Recursive Unlink
-@table @kbd
+@table @option
@item --recursive-unlink
When this option is specified, try removing files and directory hierarchies
before extracting over them. @emph{This is a dangerous option!}
as far as current permissions will allow it. This could include removal
of the contents of a full directory hierarchy.
-@node Modification Times
-@unnumberedsubsubsec Setting Modification Times
+@node Data Modification Times
+@unnumberedsubsubsec Setting Data Modification Times
-Normally, @command{tar} sets the modification times of extracted files to
-the modification times recorded for the files in the archive, but
+Normally, @command{tar} sets the data modification times of extracted
+files to the corresponding times recorded for the files in the archive, but
limits the permissions of extracted files by the current @code{umask}
setting.
-To set the modification times of extracted files to the time when
+To set the data modification times of extracted files to the time when
the files were extracted, use the @value{op-touch} option in
conjunction with @value{op-extract}.
-@table @kbd
+@table @option
@item --touch
@itemx -m
-Sets the modification time of extracted archive members to the time
+Sets the data modification time of extracted archive members to the time
they were extracted, not the time recorded for them in the archive.
Use in conjunction with @value{op-extract}.
@end table
in conjunction with the @value{op-extract} operation. @FIXME{Should be
aliased to ignore-umask.}
-@table @kbd
+@table @option
@item --preserve-permission
@itemx --same-permission
@itemx --ignore-umask
they appear on standard output concatenated, in the order they are
found in the archive.
-@table @kbd
+@table @option
@item --to-stdout
@itemx -O
Writes files to the standard output. Used in conjunction with
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
-@table @kbd
+@table @option
@item --remove-files
Remove files after adding them to the archive.
@end table
@node Starting File
@unnumberedsubsubsec Starting File
-@table @kbd
+@table @option
@item --starting-file=@var{name}
@itemx -K @var{name}
Starts an operation in the middle of an archive. Use in conjunction
@node Same Order
@unnumberedsubsubsec Same Order
-@table @kbd
+@table @option
@item --same-order
@itemx --preserve-order
@itemx -s
medium is a @dfn{pipe}, which is one a Unix redirection mechanism:
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
@end smallexample
@noindent
The command also works using short option forms:
@smallexample
-$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
+$ @w{@kbd{cd sourcedir; tar --create --file=- . | (cd targetdir; tar --extract --file=-)}}
@end smallexample
@noindent
ftp://ftp.cs.umd.edu/pub/amanda
@end smallexample
-@ifclear PUBLISH
+@FIXME{
Here is a possible plan for a future documentation about the backuping
scripts which are provided within the @GNUTAR{}
distribution.
-@smallexample
-.* dumps
-. + what are dumps
-
-. + different levels of dumps
-. - full dump = dump everything
-. - level 1, level 2 dumps etc, -
- A level n dump dumps everything changed since the last level
- n-1 dump (?)
-
-. + how to use scripts for dumps (ie, the concept)
-. - scripts to run after editing backup specs (details)
-
-. + Backup Specs, what is it.
-. - how to customize
-. - actual text of script [/sp/dump/backup-specs]
-
-. + Problems
-. - rsh doesn't work
-. - rtape isn't installed
-. - (others?)
-
-. + the --incremental option of tar
-
-. + tapes
-. - write protection
-. - types of media
-. : different sizes and types, useful for different things
-. - files and tape marks
+@itemize @bullet
+@item dumps
+ @itemize @minus
+ @item what are dumps
+ @item different levels of dumps
+ @itemize +
+ @item full dump = dump everything
+ @item level 1, level 2 dumps etc
+ A level @var{n} dump dumps everything changed since the last level
+ @var{n}-1 dump (?)
+ @end itemize
+ @item how to use scripts for dumps (ie, the concept)
+ @itemize +
+ @item scripts to run after editing backup specs (details)
+ @end itemize
+ @item Backup Specs, what is it.
+ @itemize +
+ @item how to customize
+ @item actual text of script [/sp/dump/backup-specs]
+ @end itemize
+ @item Problems
+ @itemize +
+ @item rsh doesn't work
+ @item rtape isn't installed
+ @item (others?)
+ @end itemize
+ @item the @option{--incremental} option of tar
+ @item tapes
+ @itemize +
+ @item write protection
+ @item types of media, different sizes and types, useful for different things
+ @item files and tape marks
one tape mark between files, two at end.
-. - positioning the tape
+ @item positioning the tape
MT writes two at end of write,
- backspaces over one when writing again.
-@end smallexample
-
-@end ifclear
+ backspaces over one when writing again.
+ @end itemize
+ @end itemize
+@end itemize
+}
This chapter documents both the provided shell scripts and @command{tar}
options which are more specific to usage as a backup tool.
@menu
* Full Dumps:: Using @command{tar} to Perform Full Dumps
-* Inc Dumps:: Using @command{tar} to Perform Incremental Dumps
-* incremental and listed-incremental:: The Incremental Options
+* Incremental Dumps:: Using @command{tar} to Perform Incremental Dumps
* Backup Levels:: Levels of Backups
* Backup Parameters:: Setting Parameters for Backups and Restoration
* Scripted Backups:: Using the Backup Scripts
@cindex corrupted archives
Full dumps should only be made when no other people or programs
-are modifying files in the filesystem. If files are modified while
+are modifying files in the file system. If files are modified while
@command{tar} is making the backup, they may not be stored properly in
the archive, in which case you won't be able to restore them if you
have to. (Files not being modified are written with no trouble, and do
volume label, so you can tell what this archive is even if the label
falls off the tape, or anything like that.
-Unless the filesystem you are dumping is guaranteed to fit on
+Unless the file system you are dumping is guaranteed to fit on
one volume, you will need to use the @value{op-multi-volume} option.
Make sure you have enough tapes on hand to complete the backup.
-If you want to dump each filesystem separately you will need to use
+If you want to dump each file system separately you will need to use
the @value{op-one-file-system} option to prevent @command{tar} from crossing
-filesystem boundaries when storing (sub)directories.
+file system boundaries when storing (sub)directories.
-The @value{op-incremental} option is not needed, since this is a complete
-copy of everything in the filesystem, and a full restore from this
-backup would only be done onto a completely empty disk.
+The @value{op-incremental} (@FIXME-pxref{}) option is not needed,
+since this is a complete copy of everything in the file system, and a
+full restore from this backup would only be done onto a completely
+empty disk.
Unless you are in a hurry, and trust the @command{tar} program (and your
tapes), it is a good idea to use the @value{op-verify} option, to make
it was being archived. Not all media (notably cartridge tapes) are
capable of being verified, unfortunately.
-@value{op-listed-incremental} take a file name argument always. If the
-file doesn't exist, run a level zero dump, creating the file. If the
-file exists, uses that file to see what has changed.
-
-@value{op-incremental} @FIXME{look it up}
-
-@value{op-incremental} handle old @acronym{GNU}-format incremental backup.
+@node Incremental Dumps
+@section Using @command{tar} to Perform Incremental Dumps
-This option should only be used when creating an incremental backup of
-a filesystem. When the @value{op-incremental} option is used, @command{tar}
-writes, at the beginning of the archive, an entry for each of the
-directories that will be operated on. The entry for a directory
-includes a list of all the files in the directory at the time the
-dump was done, and a flag for each file indicating whether the file
-is going to be put in the archive. This information is used when
-doing a complete incremental restore.
+@dfn{Incremental backup} is a special form of @GNUTAR{} archive that
+stores additional metadata so that exact state of the file system
+can be restored when extracting the archive.
-Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@acronym{GNU} versions of the
-@command{tar} program.
+@GNUTAR{} currently offers two options for handling incremental
+backups: @value{op-listed-incremental} and @value{op-incremental}.
-The @value{op-incremental} option means the archive is an incremental
-backup. Its meaning depends on the command that it modifies.
+The option @option{--listed-incremental} instructs tar to operate on
+an incremental archive with additional metadata stored in a standalone
+file, called a @dfn{snapshot file}. The purpose of this file is to help
+determine which files have been changed, added or deleted since the
+last backup, so that the next incremental backup will contain only
+modified files. The name of the snapshot file is given as an argument
+to the option:
-If the @value{op-incremental} option is used with @value{op-list},
-@command{tar} will list, for each directory in the archive, the list
-of files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is
-followed by an additional null and a newline to indicate the end of
-the data.
-
-If the @value{op-incremental} option is used with @value{op-extract}, then
-when the entry for a directory is found, all files that currently
-exist in that directory but are not listed in the archive @emph{are
-deleted from the directory}.
-
-This behavior is convenient when you are restoring a damaged file
-system from a succession of incremental backups: it restores the
-entire state of the file system to that which obtained when the backup
-was made. If you don't use @value{op-incremental}, the file system will
-probably fill up with files that shouldn't exist any more.
-
-@value{op-listed-incremental} handle new @acronym{GNU}-format
-incremental backup. This option handles new @acronym{GNU}-format
-incremental backup. It has much the same effect as
-@value{op-incremental}, but also the time when the dump is done and
-the list of directories dumped is written to the given
-@var{file}. When restoring, only files newer than the saved time are
-restored, and the directory list is used to speed up operations.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar} to
-use the file @var{file}, which contains information about the state
-of the filesystem at the time of the last backup, to decide which
-files to include in the archive being created. That file will then
-be updated by @command{tar}. If the file @var{file} does not exist when
-this option is specified, @command{tar} will create it, and include all
-appropriate files in the archive.
-
-The file, which is archive independent, contains the date it was last
-modified and a list of devices, inode numbers and directory names.
-@command{tar} will archive files with newer mod dates or inode change
-times, and directories with an unchanged inode number and device but
-a changed directory name. The file is updated after the files to
-be archived are determined, but before the new archive is actually
-created.
-
-@node Inc Dumps
-@section Using @command{tar} to Perform Incremental Dumps
-@UNREVISED
+@table @option
+@item --listed-incremental=@var{file}
+@itemx -g @var{file}
+ Handle incremental backups with snapshot data in @var{file}.
+@end table
-@cindex incremental dumps
-@cindex dumps, incremental
+To create an incremental backup, you would use
+@option{--listed-incremental} together with @option{--create}
+(@pxref{create}). For example:
-Performing incremental dumps is similar to performing full dumps,
-although a few more options will usually be needed.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.1.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+@end smallexample
-A standard scheme is to do a @emph{monthly} (full) dump once a month,
-a @emph{weekly} dump once a week of everything since the last monthly
-and a @emph{daily} every day of everything since the last (weekly or
-monthly) dump.
+This will create in @file{archive.1.tar} an incremental backup of
+the @file{/usr} file system, storing additional metadata in the file
+@file{/var/log/usr.snar}. If this file does not exist, it will be
+created. The created archive will then be a @dfn{level 0 backup};
+please see the next section for more on backup levels.
-Here is a sample script to dump the directory hierarchies @samp{/usr}
-and @samp{/var}.
+Otherwise, if the file @file{/var/log/usr.snar} exists, it
+determines which files are modified. In this case only these files will be
+stored in the archive. Suppose, for example, that after running the
+above command, you delete file @file{/usr/doc/old} and create
+directory @file{/usr/local/db} with the following contents:
@smallexample
-#! /bin/sh
-tar --create \
- --blocking-factor=126 \
- --file=/dev/rmt/0 \
- --label="`hostname` /usr /var `date +%Y-%m-%d`" \
- --listed-incremental=/var/log/usr-var.snar \
- --verbose \
- /usr /var
+$ @kbd{ls /usr/local/db}
+/usr/local/db/data
+/usr/local/db/index
@end smallexample
-This script uses the file @file{/var/log/usr-var.snar} as a snapshot to
-store information about the previous tar dump.
+Some time later you create another incremental backup. You will
+then see:
-The blocking factor 126 is an attempt to make the tape drive stream.
-Some tape devices cannot handle 64 kB blocks or larger, and require the
-block size to be a multiple of 1 kB; for these devices, 126 is the
-largest blocking factor that can be used.
+@smallexample
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar \
+ /usr}
+tar: usr/local/db: Directory is new
+usr/local/db/
+usr/local/db/data
+usr/local/db/index
+@end smallexample
-@node incremental and listed-incremental
-@section The Incremental Options
-@UNREVISED
+@noindent
+The created archive @file{archive.2.tar} will contain only these
+three members. This archive is called a @dfn{level 1 backup}. Notice
+that @file{/var/log/usr.snar} will be updated with the new data, so if
+you plan to create more @samp{level 1} backups, it is necessary to
+create a working copy of the snapshot file before running
+@command{tar}. The above example will then be modified as follows:
-@value{op-incremental} is used in conjunction with @value{op-create},
-@value{op-extract} or @value{op-list} when backing up and restoring file
-systems. An archive cannot be extracted or listed with the
-@value{op-incremental} option specified unless it was created with the
-option specified. This option should only be used by a script, not by
-the user, and is usually disregarded in favor of
-@value{op-listed-incremental}, which is described below.
-
-@value{op-incremental} in conjunction with @value{op-create} causes
-@command{tar} to write, at the beginning of the archive, an entry for
-each of the directories that will be archived. The entry for a
-directory includes a list of all the files in the directory at the
-time the archive was created and a flag for each file indicating
-whether or not the file is going to be put in the archive.
-
-Note that this option causes @command{tar} to create a non-standard
-archive that may not be readable by non-@acronym{GNU} versions of the
-@command{tar} program.
-
-@value{op-incremental} in conjunction with @value{op-extract} causes
-@command{tar} to read the lists of directory contents previously stored
-in the archive, @emph{delete} files in the file system that did not
-exist in their directories when the archive was created, and then
-extract the files in the archive.
-
-This behavior is convenient when restoring a damaged file system from
-a succession of incremental backups: it restores the entire state of
-the file system to that which obtained when the backup was made. If
-@value{op-incremental} isn't specified, the file system will probably
-fill up with files that shouldn't exist any more.
-
-@value{op-incremental} in conjunction with @value{op-list} causes
-@command{tar} to print, for each directory in the archive, the list of
-files in that directory at the time the archive was created. This
-information is put out in a format that is not easy for humans to
-read, but which is unambiguous for a program: each file name is
-preceded by either a @samp{Y} if the file is present in the archive,
-an @samp{N} if the file is not included in the archive, or a @samp{D}
-if the file is a directory (and is included in the archive). Each
-file name is terminated by a null character. The last file is followed
-by an additional null and a newline to indicate the end of the data.
-
-@value{op-listed-incremental} acts like @value{op-incremental}, but when
-used in conjunction with @value{op-create} will also cause @command{tar}
-to use the file @var{snapshot-file}, which contains information about
-the state of the file system at the time of the last backup, to decide
-which files to include in the archive being created. That file will
-then be updated by @command{tar}. If the file @var{file} does not exist
-when this option is specified, @command{tar} will create it, and include
-all appropriate files in the archive.
-
-The file @var{file}, which is archive independent, contains the date
-it was last modified and a list of devices, inode numbers and
-directory names. @command{tar} will archive files with newer mod dates
-or inode change times, and directories with an unchanged inode number
-and device but a changed directory name. The file is updated after
-the files to be archived are determined, but before the new archive is
-actually created.
+@smallexample
+$ @kbd{cp /var/log/usr.snar /var/log/usr.snar-1}
+$ @kbd{tar --create \
+ --file=archive.2.tar \
+ --listed-incremental=/var/log/usr.snar-1 \
+ /usr}
+@end smallexample
Incremental dumps depend crucially on time stamps, so the results are
-unreliable if you modify a file's time stamps during dumping (e.g.@:
-with the @option{--atime-preserve} option), or if you set the clock
+unreliable if you modify a file's time stamps during dumping (e.g.,
+with the @option{--atime-preserve=replace} option), or if you set the clock
backwards.
-Despite it should be obvious that a device has a non-volatile value, NFS
-devices have non-dependable values when an automounter gets in the picture.
-This led to a great deal of spurious redumping in incremental dumps,
-so it is somewhat useless to compare two NFS devices numbers over time.
-So @command{tar} now considers all NFS devices as being equal when it comes
-to comparing directories; this is fairly gross, but there does not seem
+Metadata stored in snapshot files include device numbers, which,
+obviously is supposed to be a non-volatile value. However, it turns
+out that NFS devices have undependable values when an automounter
+gets in the picture. This can lead to a great deal of spurious
+redumping in incremental dumps, so it is somewhat useless to compare
+two NFS devices numbers over time. The solution implemented currently
+is to considers all NFS devices as being equal when it comes to
+comparing directories; this is fairly gross, but there does not seem
to be a better way to go.
-@command{tar} doesn't access @var{snapshot-file} when
-@value{op-extract} or @value{op-list} are specified, but the
-@value{op-listed-incremental} option must still be given. A
-placeholder @var{snapshot-file} can be specified, e.g.,
-@file{/dev/null}.
+Note that incremental archives use @command{tar} extensions and may
+not be readable by non-@acronym{GNU} versions of the @command{tar} program.
+
+To extract from the incremental dumps, use
+@option{--listed-incremental} together with @option{--extract}
+option (@pxref{extracting files}). In this case, @command{tar} does
+not need to access snapshot file, since all the data necessary for
+extraction are stored in the archive itself. So, when extracting, you
+can give whatever argument to @option{--listed-incremental}, the usual
+practice is to use @option{--listed-incremental=/dev/null}.
+Alternatively, you can use @option{--incremental}, which needs no
+arguments. In general, @option{--incremental} (@option{-G}) can be
+used as a shortcut for @option{--listed-incremental} when listing or
+extracting incremental backups (for more information, regarding this
+option, @pxref{incremental-op}).
+
+When extracting from the incremental backup @GNUTAR{} attempts to
+restore the exact state the file system had when the archive was
+created. In particular, it will @emph{delete} those files in the file
+system that did not exist in their directories when the archive was
+created. If you have created several levels of incremental files,
+then in order to restore the exact contents the file system had when
+the last level was created, you will need to restore from all backups
+in turn. Continuing our example, to restore the state of @file{/usr}
+file system, one would do@footnote{Notice, that since both archives
+were created withouth @option{-P} option (@pxref{absolute}), these
+commands should be run from the root file system.}:
-@FIXME{this section needs to be written}
+@smallexample
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.1.tar}
+$ @kbd{tar --extract \
+ --listed-incremental=/dev/null \
+ --file archive.2.tar}
+@end smallexample
+
+To list the contents of an incremental archive, use @option{--list}
+(@pxref{list}), as usual. To obtain more information about the
+archive, use @option{--listed-incremental} or @option{--incremental}
+combined with two @option{--verbose} options@footnote{Two
+@option{--verbose} options were selected to avoid breaking usual
+verbose listing output (@option{--list --verbose}) when using in
+scripts.
+
+Versions of @GNUTAR{} up to 1.15.1 used to dump verbatim binary
+contents of the DUMPDIR header (with terminating nulls) when
+@option{--incremental} or @option{--listed-incremental} option was
+given, no matter what the verbosity level. This behavior, and,
+especially, the binary output it produced were considered incovenient
+and were changed in version 1.16}:
+
+@smallexample
+@kbd{tar --list --incremental --verbose --verbose archive.tar}
+@end smallexample
+
+This command will print, for each directory in the archive, the list
+of files in that directory at the time the archive was created. This
+information is put out in a format which is both human-readable and
+unambiguous for a program: each file name is printed as
+
+@smallexample
+@var{x} @var{file}
+@end smallexample
+
+@noindent
+where @var{x} is a letter describing the status of the file: @samp{Y}
+if the file is present in the archive, @samp{N} if the file is not
+included in the archive, or a @samp{D} if the file is a directory (and
+is included in the archive).@FIXME-xref{dumpdir format}. Each such
+line is terminated by a newline character. The last line is followed
+by an additional newline to indicate the end of the data.
+
+@anchor{incremental-op}The option @option{--incremental} (@option{-G})
+gives the same behavior as @option{--listed-incremental} when used
+with @option{--list} and @option{--extract} options. When used with
+@option{--create} option, it creates an incremental archive without
+creating snapshot file. Thus, it is impossible to create several
+levels of incremental backups with @option{--incremental} option.
@node Backup Levels
@section Levels of Backups
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. This file is usually located
-in @file{/etc/backup} directory. @FIXME-xref{Script Syntax} Once the
+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
+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. @value{xref-incremental}, and
-@value{xref-listed-incremental}, before making such an attempt.
+it is easier to use the scripts. @value{xref-incremental}, before
+making such an attempt.
@node Backup Parameters
@section Setting Parameters for Backups and Restoration
before using these scripts.
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).
+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
+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
@subsection General-Purpose Variables
@defvr {Backup variable} ADMINISTRATOR
-The user name of the backup administrator. @code{Backup} scripts
+The user name of the backup administrator. @code{Backup} scripts
sends a backup report to this address.
@end defvr
@defvr {Backup variable} BACKUP_HOUR
-The hour at which the backups are done. This can be a number from 0
+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}.
-This variable is used by @code{backup}. Its value may be overridden
+This variable is used by @code{backup}. Its value may be overridden
using @option{--time} option (@pxref{Scripted Backups}).
@end defvr
@defvr {Backup variable} TAPE_FILE
-The device @command{tar} writes the archive to. If @var{TAPE_FILE}
+The device @command{tar} writes the archive to. If @var{TAPE_FILE}
is a remote archive (@pxref{remote-dev}), backup script will suppose
-that your @command{mt} is able to access remote devices. If @var{RSH}
+that your @command{mt} is able to access remote devices. If @var{RSH}
(@pxref{RSH}) is set, @option{--rsh-command} option will be added to
-invocations of @command{mt}.
+invocations of @command{mt}.
@end defvr
@defvr {Backup variable} BLOCKING
@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
+(for @code{restore}). You can include any directory
name in the list --- subdirectories on that file system will be
included, regardless of how they may look to other networked machines.
Subdirectories on other file systems will be ignored.
the host machine must have @GNUTAR{} installed, and
must be able to access the directory containing the backup scripts and
their support files using the same file name that is used on the
-machine where the scripts are run (ie. what @command{pwd} will print
+machine where the scripts are run (ie. what @command{pwd} will print
when in that directory on that machine). If the host that contains
the file system does not have this capability, you can specify another
host as long as it can access the file system through NFS.
If the list of file systems is very long you may wish to put it
-in a separate file. This file is usually named
+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}.
+A path to the file containing the list of the file systems to backup
+or restore. By default it is @file{/etc/backup/dirs}.
@end defvr
@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
+(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
+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}.
+or restore. By default it is @file{/etc/backup/files}.
@end defvr
@defvr {Backup variable} MT
@defvr {Backup variable} RSH
@anchor{RSH}
-Full file name of @command{rsh} binary or its equivalent. You may wish to
-set it to @code{ssh}, to improve security. In this case you will have
+Full file name of @command{rsh} binary or its equivalent. You may wish to
+set it to @code{ssh}, to improve security. In this case you will have
to use public key authentication.
@end defvr
@defvr {Backup variable} RSH_COMMAND
-Full file name of @command{rsh} binary on remote mashines. This will
+Full file name of @command{rsh} binary on remote mashines. This will
be passed via @option{--rsh-command} option to the remote invocation
-of @GNUTAR{}.
+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.
+by all the machines which have file systems to be dumped.
@end defvr
@defvr {Backup variable} XLIST
-Name of @dfn{exclude file list}. An @dfn{exclude file list} is a file
+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
+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).
+(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
+Time to sleep between dumps of any two successive file systems
This variable affects only @code{backup}.
@end defvr
@defvr {Backup variable} DUMP_REMIND_SCRIPT
Script to be run when it's time to insert a new tape in for the next
-volume. Administrators may want to tailor this script for their site.
+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.
@defvr {Backup variable} TAR
-Full file name of the @GNUTAR{} executable. If this is not set, backup
+Full file name of the @GNUTAR{} executable. If this is not set, backup
scripts will search @command{tar} in the current shell path.
@end defvr
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:
+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:
+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
@end defvr
@defvr {Backup variable} MT_REWIND
-The name of @dfn{rewind} function. The default definition is as
+The name of @dfn{rewind} function. The default definition is as
follows:
@smallexample
@end defvr
@defvr {Backup variable} MT_OFFLINE
-The name of the function switching the tape off line. By default
+The name of the function switching the tape off line. By default
it is defined as follows:
@smallexample
@defvr {Backup variable} MT_STATUS
The name of the function used to obtain the status of the archive device,
-including error count. Default definition:
+including error count. Default definition:
@smallexample
MT_STATUS=mt_status
@subsection User Hooks
@dfn{User hooks} are shell functions executed before and after
-each @command{tar} invocation. Thus, there are @dfn{backup
+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
+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}
Name or IP address of the host machine being dumped or restored.
@item fs
-Full path name to the filesystem being dumped or restored.
+Full path name to the file system being dumped or restored.
@item fsname
-Filesystem name with directory separators replaced with colons. This
-is useful e.g. for creating unique files.
+File system name with directory separators replaced with colons. This
+is useful, e.g., for creating unique files.
@end table
@end deffn
Following variables keep the names of user hook functions
@defvr {Backup variable} DUMP_BEGIN
-Dump begin function. It is executed before dumping the filesystem.
+Dump begin function. It is executed before dumping the file system.
@end defvr
@defvr {Backup variable} DUMP_END
-Executed after dumping the filesystem.
+Executed after dumping the file system.
@end defvr
@defvr {Backup variable} RESTORE_BEGIN
-Executed before restoring the filesystem.
+Executed before restoring the file system.
@end defvr
@defvr {Backup variable} RESTORE_END
-Executed after restoring the filesystem.
+Executed after restoring the file system.
@end defvr
@node backup-specs example
backup --level=@var{level} --time=@var{time}
@end smallexample
-The @option{level} option requests the dump level. Thus, to produce
+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-}
+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}
+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:
+run. @var{Time} may take three forms:
@table @asis
@item @var{hh}:@var{mm}
@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}
+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}
@section Using the Restore Script
To restore files that were archived using a scripted backup, use the
-@code{restore} script. Its usage is quite straightforward. In the
+@code{restore} script. Its usage is quite straightforward. In the
simplest form, invoke @code{restore --all}, it will
-then restore all the filesystems and files specified in
+then restore all the file systems and files specified in
@file{backup-specs} (@pxref{General-Purpose Variables,BACKUP_DIRS}).
-You may select the filesystems (and/or files) to restore by
+You may select the file systems (and/or files) to restore by
giving @code{restore} list of @dfn{patterns} in its command
-line. For example, running
+line. For example, running
@smallexample
restore 'albert:*'
@end smallexample
@noindent
-will restore all filesystems on the machine @samp{albert}. A more
+will restore all file systems on the machine @samp{albert}. A more
complicated example:
@smallexample
@end smallexample
@noindent
-This command will restore all filesystems on the machine @samp{albert}
-as well as @file{/var} filesystem on all machines.
+This command will restore all file systems on the machine @samp{albert}
+as well as @file{/var} file system on all machines.
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,
+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
@table @option
@item -a
@itemx --all
-Restore all filesystems and files specified in @file{backup-specs}
+Restore all file systems and files specified in @file{backup-specs}
@item -l @var{level}
@itemx --level=@var{level}
@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}
+Set verbosity level. The higher the level is, the more debugging
+information will be output during execution. Devault @var{level}
is 100, which means the highest debugging level.
@item -h
system if they were not in the file system when the archive was made.
@end quotation
-@value{xref-incremental}, and @value{ref-listed-incremental},
-for an explanation of how the script makes that determination.
+@value{xref-incremental}, for an explanation of how the script makes
+that determination.
@node Choosing
@chapter Choosing Files and Names for @command{tar}
* Wildcards::
* after:: Operating Only on New Files
* recurse:: Descending into Directories
-* one:: Crossing Filesystem Boundaries
+* one:: Crossing File System Boundaries
@end menu
@node file
option allows you to either specify or name a file to use as the archive
instead of the default archive file location.
-@table @kbd
+@table @option
@item --file=@var{archive-name}
@itemx -f @var{archive-name}
Name the archive to create or operate on. Use in conjunction with
If you do not name the archive, @command{tar} uses the value of the
environment variable @env{TAPE} as the file name for the archive. If
that is not available, @command{tar} uses a default, compiled-in archive
-name, usually that for tape unit zero (ie. @file{/dev/tu00}).
+name, usually that for tape unit zero (ie. @file{/dev/tu00}).
@command{tar} always needs an archive name.
If you use @file{-} as an @var{archive-name}, @command{tar} reads the
"notable tar usages".}
@smallexample
-$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
+$ @kbd{cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)}
@end smallexample
@FIXME{help!}
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
+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.
@value{op-files-from} option to @command{tar}. Give the name of the file
which contains the list of files to include as the argument to
@option{--files-from}. In the list, the file names should be separated by
-newlines. You will frequently use this option when you have generated
+newlines. You will frequently use this option when you have generated
the list of files to archive with the @command{find} utility.
-@table @kbd
+@table @option
@item --files-from=@var{file name}
@itemx -T @var{file name}
Get names to extract or create from file @var{file name}.
more information.)
@smallexample
-$ @kbd{find . -size -400 -print > small-files}
+$ @kbd{find . -size -400 -print > small-files}
$ @kbd{tar -c -v -z -T small-files -f little.tgz}
@end smallexample
@noindent
In this example, @command{tar} will first switch to @file{/etc}
directory and add files @file{passwd} and @file{hosts} to the
-archive. Then it will change to @file{/lib} directory and will archive
-the file @file{libc.a}. Thus, the resulting archive @file{foo.tar} will
+archive. Then it will change to @file{/lib} directory and will archive
+the file @file{libc.a}. Thus, the resulting archive @file{foo.tar} will
contain:
@smallexample
@noindent
Notice that the option parsing algorithm used with @option{-T} is
-stricter than the one used by shell. Namely, when specifying option
+stricter than the one used by shell. Namely, when specifying option
arguments, you should observe the following rules:
@itemize @bullet
@item
When using short (single-letter) option form, its argument must
immediately follow the option letter, without any intervening
-whitespace. For example: @code{-Cdir}.
+whitespace. For example: @code{-Cdir}.
@item
When using long option form, the option argument must be separated
-from the option by a single equal sign. No whitespace is allowed on
-any side of the equal sign. For example: @code{--directory=dir}.
+from the option by a single equal sign. No whitespace is allowed on
+any side of the equal sign. For example: @code{--directory=dir}.
@item
For both short and long option forms, the option argument can be given
@cindex @option{--add-file}
If you happen to have a file whose name starts with @samp{-},
precede it with @option{--add-file} option to prevent it from
-being recognized as an option. For example: @code{--add-file --my-file}.
+being recognized as an option. For example: @code{--add-file --my-file}.
@menu
* nul::
@end menu
@node nul
-@subsection @kbd{NUL} Terminated File Names
+@subsection @code{NUL} Terminated File Names
-@cindex File names, terminated by @kbd{NUL}
-@cindex @kbd{NUL} terminated file names
+@cindex File names, terminated by @code{NUL}
+@cindex @code{NUL} terminated file names
The @value{op-null} option causes @value{op-files-from} to read file
names terminated by a @code{NUL} instead of a newline, so files whose
names contain newlines can be archived using @option{--files-from}.
-@table @kbd
+@table @option
@item --null
-Only consider @kbd{NUL} terminated file names, instead of files that
+Only consider @code{NUL} terminated file names, instead of files that
terminate in a newline.
@end table
This example shows how to use @command{find} to generate a list of files
larger than 800K in length and put that list into a file called
-@file{long-files}. The @option{-print0} option to @command{find} is just
-like @option{-print}, except that it separates files with a @kbd{NUL}
+@file{long-files}. The @option{-print0} option to @command{find} is just
+like @option{-print}, except that it separates files with a @code{NUL}
rather than with a newline. You can then run @command{tar} with both the
@option{--null} and @option{-T} options to specify that @command{tar} get the
files from that file, @file{long-files}, to create the archive
@file{big.tgz}. The @option{--null} option to @command{tar} will cause
-@command{tar} to recognize the @kbd{NUL} separator between files.
+@command{tar} to recognize the @code{NUL} separator between files.
@smallexample
-$ @kbd{find . -size +800 -print0 > long-files}
+$ @kbd{find . -size +800 -print0 > long-files}
$ @kbd{tar -c -v --null --files-from=long-files --file=big.tar}
@end smallexample
To avoid operating on files whose names match a particular pattern,
use the @value{op-exclude} or @value{op-exclude-from} options.
-@table @kbd
+@table @option
@item --exclude=@var{pattern}
Causes @command{tar} to ignore files that match the @var{pattern}.
@end table
You may give multiple @option{--exclude} options.
-@table @kbd
+@table @option
@item --exclude-from=@var{file}
@itemx -X @var{file}
Causes @command{tar} to ignore files that match the patterns listed in
@FIXME{do the exclude options files need to have stuff separated by
newlines the same as the files-from option does?}
-@table @kbd
+@table @option
@item --exclude-caches
Causes @command{tar} to ignore directories containing a cache directory tag.
@end table
@item --anchored
@itemx --no-anchored
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}.
+of the name's components. Otherwise, the pattern can match any
+subsequence. Default is @option{--no-anchored}.
@item --ignore-case
@itemx --no-ignore-case
@samp{*} or @samp{?} for example, are replaced and expanded into all
existing files matching the given pattern. However, @command{tar} often
uses wildcard patterns for matching (or globbing) archive members instead
-of actual files in the filesystem. Wildcard patterns are also used for
+of actual files in the file system. Wildcard patterns are also used for
verifying volume labels of @command{tar} archives. This section has the
purpose of explaining wildcard syntax for @command{tar}.
@node after
@section Operating Only on New Files
@cindex Excluding file by age
+@cindex Data Modification time, excluding files by
@cindex Modification time, excluding files by
@cindex Age, excluding files by
@UNREVISED
The @value{op-after-date} option causes @command{tar} to only work on files
-whose modification or inode-changed times are newer than the @var{date}
+whose data modification or status change times are newer than the @var{date}
given. If @var{date} starts with @samp{/} or @samp{.}, it is taken to
-be a file name; the last-modified time of that file is used as the date.
+be a file name; the data modification time of that file is used as the date.
If you use this option when creating or appending to an archive,
the archive will only include new files. If you use @option{--after-date}
when extracting an archive, @command{tar} will only extract files newer
than the @var{date} you specify.
If you only want @command{tar} to make the date comparison based on
-modification of the actual contents of the file (rather than inode
+modification of the file's data (rather than status
changes), then use the @value{op-newer-mtime} option.
You may use these options with any operation. Note that these options
specify a particular date against which @command{tar} can compare when
deciding whether or not to archive the files.
-@table @kbd
+@table @option
@item --after-date=@var{date}
@itemx --newer=@var{date}
@itemx -N @var{date}
Only store files newer than @var{date}.
-Acts on files only if their modification or inode-changed times are
+Acts on files only if their data modification or status change times are
later than @var{date}. Use in conjunction with any operation.
If @var{date} starts with @samp{/} or @samp{.}, it is taken to be a file
-name; the last-modified time of that file is used as the date.
+name; the data modification time of that file is used as the date.
@item --newer-mtime=@var{date}
-Acts like @value{op-after-date}, but only looks at modification times.
+Acts like @value{op-after-date}, but only looks at data modification times.
@end table
-These options limit @command{tar} to only operating on files which have
-been modified after the date specified. A file is considered to have
-changed if the contents have been modified, or if the owner,
+These options limit @command{tar} to operate only on files which have
+been modified after the date specified. A file's status is considered to have
+changed if its contents have been modified, or if its owner,
permissions, and so forth, have been changed. (For more information on
how to specify a date, see @ref{Date input formats}; remember that the
entire date argument must be quoted if it contains any spaces.)
-Gurus would say that @value{op-after-date} tests both the @code{mtime}
-(time the contents of the file were last modified) and @code{ctime}
-(time the file's status was last changed: owner, permissions, etc)
-fields, while @value{op-newer-mtime} tests only @code{mtime} field.
+Gurus would say that @value{op-after-date} tests both the data
+modification time (@code{mtime}, the time the contents of the file
+were last modified) and the status change time (@code{ctime}, the time
+the file's status was last changed: owner, permissions, etc.@:)
+fields, while @value{op-newer-mtime} tests only the @code{mtime}
+field.
To be precise, @value{op-after-date} checks @emph{both} @code{mtime} and
@code{ctime} and processes the file if either one is more recent than
@strong{Please Note:} @value{op-after-date} and @value{op-newer-mtime}
should not be used for incremental backups. Some files (such as those
in renamed directories) are not selected properly by these options.
-@xref{incremental and listed-incremental}.
+@xref{Incremental Dumps}.
@end quotation
@noindent
archive; see @ref{files} for more information on using @command{find} with
@command{tar}, or look.
-@table @kbd
+@table @option
@item --no-recursion
Prevents @command{tar} from recursively descending directories.
directory entries themselves, but does not descend on them
recursively. Many people use @command{find} for locating files they
want to back up, and since @command{tar} @emph{usually} recursively
-descends on directories, they have to use the @samp{@w{! -d}} option
+descends on directories, they have to use the @samp{@w{! -d}} option
to @command{find} @FIXME{needs more explanation or a cite to another
info file}as they usually do not want all the files in a directory.
They then use the @value{op-files-from} option to archive the files
other than @file{grape/concord}.
@node one
-@section Crossing Filesystem Boundaries
+@section Crossing File System Boundaries
@cindex File system boundaries, not crossing
@UNREVISED
@command{tar} will still archive files explicitly named on the command line
or through @value{op-files-from}, regardless of where they reside.
-@table @kbd
+@table @option
@item --one-file-system
@itemx -l
Prevents @command{tar} from crossing file system boundaries when
The @option{--one-file-system} option causes @command{tar} to modify its
normal behavior in archiving the contents of directories. If a file in
-a directory is not on the same filesystem as the directory itself, then
+a directory is not on the same file system as the directory itself, then
@command{tar} will not archive that file. If the file is a directory
itself, @command{tar} will not archive anything beneath it; in other words,
@command{tar} will not cross mount points.
working directory to the directory @var{directory} after that point in
the list.
-@table @kbd
+@table @option
@item --directory=@var{directory}
@itemx -C @var{directory}
Changes the working directory in the middle of a command line.
@option{--directory} option.
When using @option{--files-from} (@pxref{files}), you can put various
-@command{tar} options (including @option{-C}) in the file list. Notice,
+@command{tar} options (including @option{-C}) in the file list. Notice,
however, that in this case the option and its argument may not be
-separated by whitespace. If you use short option, its argument must
+separated by whitespace. If you use short option, its argument must
either follow the option letter immediately, without any intervening
-whitespace, or occupy the next line. Otherwise, if you use long
+whitespace, or occupy the next line. Otherwise, if you use long
option, separate its argument by an equal sign.
For instance, the file list for the above example will be:
@end smallexample
Notice also that you can only use the short option variant in the file
-list, i.e. always use @option{-C}, not @option{--directory}.
+list, i.e., always use @option{-C}, not @option{--directory}.
The interpretation of @value{op-directory} is disabled by
@value{op-null} option.
@subsection Absolute File Names
@UNREVISED
-@table @kbd
+@table @option
@item -P
@itemx --absolute-names
Do not strip leading slashes from file names, and permit file names
leading slashes from member names when putting members into the
archive. For example, if you ask @command{tar} to add the file
@file{/bin/ls} to an archive, it will do so, but the member name will
-be @file{bin/ls}.
+be @file{bin/ls}.@footnote{A side effect of this is that when
+@option{--create} is used with @option{--verbose} the resulting output
+is not, generally speaking, the same as the one you'd get running
+@kbd{tar --list} command. This may be important if you use some
+scripts for comparing both outputs. @xref{listing member and file names},
+for the information on how to handle this case.}
If you use the @value{op-absolute-names} option, @command{tar} will do
none of these transformations.
@FIXME{Is write access an issue?}
-@table @kbd
+@table @option
@item --absolute-names
Preserves full file names (including superior directory names) when
archiving files. Preserves leading slash when extracting files.
@table @asis
@item gnu
-Format used by @GNUTAR{} versions up to 1.13.25. This format derived
+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
+sparse file handling and incremental archives. Unfortunately these
features were implemented in a way incompatible with other archive
formats.
Format used by @GNUTAR{} of versions prior to 1.12.
@item v7
-Archive format, compatible with the V7 implementation of tar. This
-format imposes a number of limitations. The most important of them
+Archive format, compatible with the V7 implementation of tar. This
+format imposes a number of limitations. The most important of them
are:
@enumerate
@end enumerate
This format has traditionally been used by Automake when producing
-Makefiles. This practice will change in the future, in the meantime,
+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:
+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
+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
@item star
Format used by J@"org Schilling @command{star}
-implementation. @GNUTAR{} is able to read @samp{star} archives but
+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
+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
formats:
@multitable @columnfractions .10 .20 .20 .20 .20
-@item Format @tab UID @tab File Size @tab Path Name @tab Devn
+@headitem Format @tab UID @tab File Size @tab Path Name @tab Devn
@item gnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
@item oldgnu @tab 1.8e19 @tab Unlimited @tab Unlimited @tab 63
@item v7 @tab 2097151 @tab 8GB @tab 99 @tab n/a
@end multitable
The default format for @GNUTAR{} is defined at compilation
-time. You may check it by running @command{tar --help}, and examining
-the last lines of its output. Usually, @GNUTAR{} is configured
+time. You may check it by running @command{tar --help}, and examining
+the last lines of its output. Usually, @GNUTAR{} is configured
to create archives in @samp{gnu} format, however, future version will
switch to @samp{posix}.
other kind of special files. Do not attempt to save sparse files or
contiguous files as such. Let's discuss a few more problems, in turn.
+@FIXME{Discuss GNU extensions (incremental backups, multi-volume
+archives and archive labels) in GNU and PAX formats.}
+
@menu
* Portable Names:: Portable Names
* dereference:: Symbolic Links
Normally, when @command{tar} archives a symbolic link, it writes a
block to the archive naming the target of the link. In that way, the
-@command{tar} archive is a faithful record of the filesystem contents.
+@command{tar} archive is a faithful record of the file system contents.
@value{op-dereference} is used with @value{op-create}, and causes
@command{tar} to archive the files symbolic links point to, instead of
the links themselves. When this option is used, when @command{tar}
versions, specify the @value{op-format-v7} option in
conjunction with the @value{op-create} (@command{tar} also
accepts @option{--portability} or @samp{op-old-archive} for this
-option). When you specify it,
+option). When you specify it,
@command{tar} leaves out information about directories, pipes, fifos,
contiguous files, and device files, and specifies file ownership by
group and user IDs instead of group and user names.
@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
+@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,
+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}.
@command{tar} programs that follow it.
In the majority of cases, @command{tar} will be configured to create
-this format by default. This will change in the future releases, since
+this format by default. This will change in the future releases, since
we plan to make @samp{posix} format the default.
To force creation a @GNUTAR{} archive, use option
-@value{op-format-gnu}.
-
-Some @command{tar} options are currently basing on @GNUTAR{}
-format, and can therefore be used only with @samp{gnu}
-or @samp{oldgnu} archive formats. The list of such options follows:
-
-@itemize @bullet
-@item @value{op-label}, when used with @value{op-create}.
-@item @value{op-incremental}
-@item @value{op-multi-volume}
-@end itemize
-
-These options will be re-implemented for the @samp{posix} archive
-format in the future.
+@value{op-format-gnu}.
@node posix
@subsection @GNUTAR{} and @acronym{POSIX} @command{tar}
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}:
-
-@itemize @bullet
-@item @value{op-label}, when used with @value{op-create}.
-@item @value{op-incremental}
-@item @value{op-multi-volume}
-@end itemize
-
-This restriction will disappear in the future versions.
@node Checksumming
@subsection Checksumming Problems
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. @acronym{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,
@cindex Compressed archives
@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
+@GNUTAR{} is able to create and read compressed archives. It supports
+@command{gzip} and @command{bzip2} compression programs. For backward
compatibilty, it also supports @command{compress} command, although
we strongly recommend against using it, since there is a patent
covering the algorithm it uses and you could be sued for patent
-infringement merely by running @command{compress}! Besides, it is less
+infringement merely by running @command{compress}! Besides, it is less
effective than @command{gzip} and @command{bzip2}.
Creating a compressed archive is simple: you just specify a
@dfn{compression option} along with the usual archive creation
-commands. The compression option is @option{-z} (@option{--gzip}) to
+commands. The compression option is @option{-z} (@option{--gzip}) to
create a @command{gzip} compressed archive, @option{-j}
(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
@option{-Z} (@option{--compress}) to use @command{compress} program.
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
+automatically. Thus, the following commands will list and extract the
archive created in previous example:
@smallexample
The only case when you have to specify a decompression option while
reading the archive is when reading from a pipe or from a tape drive
-that does not support random access. However, in this case @GNUTAR{}
-will indicate which option you should use. For example:
+that does not support random access. However, in this case @GNUTAR{}
+will indicate which option you should use. For example:
@smallexample
$ @kbd{cat archive.tar.gz | tar tf -}
-tar: Archive is compressed. Use -z option
+tar: Archive is compressed. Use -z option
tar: Error is not recoverable: exiting now
@end smallexample
@end smallexample
Notice also, that there are several restrictions on operations on
-compressed archives. First of all, compressed archives cannot be
-modified, i.e. you cannot update (@value{op-update}) them or delete
-(@value{op-delete}) members from them. Likewise, you cannot append
+compressed archives. First of all, compressed archives cannot be
+modified, i.e., you cannot update (@value{op-update}) them or delete
+(@value{op-delete}) members from them. Likewise, you cannot append
another @command{tar} archive to a compressed archive using
-@value{op-append}). Secondly, multi-volume archives cannot be
+@value{op-append}). Secondly, multi-volume archives cannot be
compressed.
The following table summarizes compression options used by @GNUTAR{}.
-@table @kbd
+@table @option
@item -z
@itemx --gzip
@itemx --ungzip
@command{compress}.
@item --use-compress-program=@var{prog}
-Use external compression program @var{prog}. Use this option if you
-have a compression program that @GNUTAR{} does not support. There
+Use external compression program @var{prog}. Use this option if you
+have a compression program that @GNUTAR{} does not support. There
are two requirements to which @var{prog} should comply:
First, when called without options, it should read data from standard
input, compress it and output it on standard output.
Secondly, if called with @option{-d} argument, it should do exactly
-the opposite, i.e. read the compressed data from the standard input
+the opposite, i.e., read the compressed data from the standard input
and produce uncompressed data on the standard output.
@end table
@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
+to do it now. I would like to use @value{op-gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
to use :-)), basically adding ECC protection on top of compression.
@cindex Sparse Files
@UNREVISED
-@table @kbd
+@table @option
@item -S
@itemx --sparse
Handle sparse files efficiently.
@acronym{GNU} options. For now, it is an option needing to be specified on
the command line with the creation or updating of an archive.
-Files in the filesystem occasionally have ``holes.'' A hole in a file
+Files in the file system occasionally have ``holes.'' A hole in a file
is a section of the file's contents which was never written. The
contents of a hole read as all zeros. On many operating systems,
actual disk storage is not allocated for holes, but they are counted
@command{tar} ignores the @value{op-sparse} option when reading an archive.
-@table @kbd
+@table @option
@item --sparse
@itemx -S
Files stored sparsely in the file system are represented sparsely in
@section Handling File Attributes
@UNREVISED
-When @command{tar} reads files, this causes them to have the access
-times updated. To have @command{tar} attempt to set the access times
-back to what they were before they were read, use the
-@value{op-atime-preserve} option.
+When @command{tar} reads files, it updates their access times. To
+avoid this, use the @value{op-atime-preserve} option, which can either
+reset the access time retroactively or avoid changing it in the first
+place.
Handling of file attributes
-@table @kbd
+@table @option
@item --atime-preserve
-Preserve access times on files that are read.
-This doesn't work for files that
-you don't own, unless you're root, and it doesn't interact with
-incremental dumps nicely (@pxref{Backups}), and it can set access or
-modification times incorrectly if other programs access the file while
-@command{tar} is running; but it is good enough for some purposes.
+@itemx --atime-preserve=replace
+@itemx --atime-preserve=system
+Preserve the access times of files that are read. This works only for
+files that you own, unless you have superuser privileges.
+
+@value{op-atime-preserve-replace} works on most systems, but it also
+restores the data modification time and updates the status change
+time. Hence it doesn't interact with incremental dumps nicely
+(@pxref{Backups}), and it can set access or data modification times
+incorrectly if other programs access the file while @command{tar} is
+running.
+
+@value{op-atime-preserve-system} avoids changing the access time in
+the first place, if the operating system supports this.
+Unfortunately, this may or may not work on any given operating system
+or file system. If @command{tar} knows for sure it won't work, it
+complains right away.
+
+Currently @option{--atime-preserve} with no operand defaults to
+@value{op-atime-preserve-replace}, but this is intended to change to
+@value{op-atime-preserve-system} when the latter is better-supported.
@item -m
@itemx --touch
-Do not extract file modified time.
+Do not extract data modification time.
-When this option is used, @command{tar} leaves the modification times
-of the files it extracts as the time when the files were extracted,
-instead of setting it to the time recorded in the archive.
+When this option is used, @command{tar} leaves the data modification times
+of the files it extracts as the times when the files were extracted,
+instead of setting it to the times recorded in the archive.
This option is meaningless with @value{op-list}.
an emergency floppy with different passwd/group files for example.
It is otherwise impossible to extract files with the right ownerships
if the password file in use during the extraction does not match the
-one belonging to the filesystem(s) being extracted. This occurs,
+one belonging to the file system(s) being extracted. This occurs,
for example, if you are restoring your files after a major crash and
had booted from an emergency floppy with no password file or put your
disk into another machine to do the restore.
Extract all protection information.
This option causes @command{tar} to set the modes (access permissions) of
-extracted files exactly as recorded in the archive. If this option
+extracted files exactly as recorded in the archive. If this option
is not used, the current @code{umask} setting limits the permissions
-on extracted files. This option is by default enabled when
+on extracted files. This option is by default enabled when
@command{tar} is executed by a superuser.
Physically, an archive consists of a series of file entries terminated
by an end-of-archive entry, which consists of two 512 blocks of zero
-bytes. A file
+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
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 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
+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.
permissions, the mode bit(s) specifying those special permissions
are ignored. Modes which are not supported by the operating system
restoring files from the archive will be ignored. Unsupported modes
-should be faked up when creating or updating an archive; e.g.@: the
+should be faked up when creating or updating an archive; e.g., the
group permission could be copied from the @emph{other} permission.
The @code{uid} and @code{gid} fields are the numeric user and group
are archived with this field specified as zero. @FIXME-xref{Modifiers, in
particular the @value{op-incremental} option.}
-The @code{mtime} field is the modification time of the file at the time
-it was archived. It is the ASCII representation of the octal value of
-the last time the file was modified, represented as an integer number of
+The @code{mtime} field is the data modification time of the file at
+the time it was archived. It is the ASCII representation of the octal
+value of the last time the file's contents were modified, represented
+as an integer number of
seconds since January 1, 1970, 00:00 Coordinated Universal Time.
The @code{chksum} field is the ASCII representation of the octal value
action occurs, @command{tar} issues a warning to the standard error.
The @code{atime} and @code{ctime} fields are used in making incremental
-backups; they store, respectively, the particular file's access time
-and last inode-change time.
+backups; they store, respectively, the particular file's access and
+status change times.
The @code{offset} is used by the @value{op-multi-volume} option, when
making a multi-volume archive. The offset is number of bytes into
@quotation
Is there any differences between the ability to recover crashed
-archives between the two of them. (Is there any chance of recovering
+archives between the two of them. (Is there any chance of recovering
crashed archives at all.)
@end quotation
@section Device Selection and Switching
@UNREVISED
-@table @kbd
+@table @option
@item -f [@var{hostname}:]@var{file}
@itemx --file=[@var{hostname}:]@var{file}
Use archive file or device @var{file} on @var{hostname}.
If the file name contains a @samp{:}, it is interpreted as
@samp{hostname:file name}. If the @var{hostname} contains an @dfn{at}
-sign (@kbd{@@}), it is treated as @samp{user@@hostname:file name}. In
+sign (@samp{@@}), it is treated as @samp{user@@hostname:file name}. In
either case, @command{tar} will invoke the command @command{rsh} (or
@command{remsh}) to start up an @command{/usr/libexec/rmt} on the remote
-machine. If you give an alternate login name, it will be given to the
+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
+@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
+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
+---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}
too. The installer could also check for @samp{DEFTAPE} in
@file{<sys/mtio.h>}.
-@table @kbd
+@table @option
@item --force-local
Archive file is local even if it contains a colon.
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. It is compiled and
+California, but can be freely distributed. It is compiled and
installed by default.
@cindex absolute file names
The data in an archive is grouped into blocks, which are 512 bytes.
Blocks are read and written in whole number multiples called
-@dfn{records}. The number of blocks in a record (ie. the size of a
+@dfn{records}. The number of blocks in a record (ie. the size of a
record in units of 512 bytes) is called the @dfn{blocking factor}.
The @value{op-blocking-factor} option specifies the blocking factor of
-an archive. The default blocking factor is typically 20 (ie.@:
+an archive. The default blocking factor is typically 20 (i.e.,
10240 bytes), but can be specified at installation. To find out
the blocking factor of an existing archive, use @samp{tar --list
--file=@var{archive-name}}. This may not work on some devices.
Records are separated by gaps, which waste space on the archive media.
If you are archiving on magnetic tape, using a larger blocking factor
(and therefore larger records) provides faster throughput and allows you
-to fit more data on a tape (because there are fewer gaps). If you are
+to fit more data on a tape (because there are fewer gaps). If you are
archiving on cartridge, a very large blocking factor (say 126 or more)
-greatly increases performance. A smaller blocking factor, on the other
+greatly increases performance. A smaller blocking factor, on the other
hand, may be useful when archiving small files, to avoid archiving lots
of nulls as @command{tar} fills out the archive to the end of the record.
In general, the ideal record size depends on the size of the
blocking factor (particularly if you're not sure what the blocking factor
is), you can usually use the @value{op-read-full-records} option while
specifying a blocking factor larger then the blocking factor of the archive
-(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
+(ie. @samp{tar --extract --read-full-records --blocking-factor=300}.
@xref{list}, for more information on the @value{op-list}
operation. @xref{Reading}, for a more detailed explanation of that option.
-@table @kbd
+@table @option
@item --blocking-factor=@var{number}
@itemx -b @var{number}
Specifies the blocking factor of an archive. Can be used with any
Device blocking
-@table @kbd
+@table @option
@item -b @var{blocks}
@itemx --blocking-factor=@var{blocks}
Set record size to @math{@var{blocks} * 512} bytes.
data on the tape will be overwritten (unless it is no longer needed).
Before reading an archive, you should make sure the tape head is at
the beginning of the archive you want to read. (The @code{restore}
-script will find the archive automatically. @FIXME-xref{Scripted Restoration}@xref{mt}, for
+script will find the archive automatically. @FIXME-xref{Scripted Restoration}@xref{mt}, for
an explanation of the tape moving utility.
If you want to add new archive file entries to a tape, you should
@FIXME{is there any use for record operations?}
-@table @kbd
+@table @option
@item eof
@itemx weof
Writes @var{number} tape marks at the current position on the tape.
Moves tape position back @var{number} files.
@item rewind
-Rewinds the tape. (Ignores @var{number}).
+Rewinds the tape. (Ignores @var{number}).
@item offline
@itemx rewoff1
-Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
+Rewinds the tape and takes the tape device off-line. (Ignores @var{number}).
@item status
Prints status information about the tape unit.
successful, 1 if the command was unrecognized, and 2 if an operation
failed.
-@FIXME{New node on how to find an archive?}
-
-If you use @value{op-extract} with the @value{op-label} option specified,
-@command{tar} will read an archive label (the tape head has to be positioned
-on it) and print an error if the archive label doesn't match the
-@var{archive-name} specified. @var{archive-name} can be any regular
-expression. If the labels match, @command{tar} extracts the archive.
-@value{xref-label}.
-@FIXME-xref{Matching Format Parameters}@FIXME{fix cross
-references}@samp{tar --list --label} will cause @command{tar} to print the
-label.
-
-@FIXME{Program to list all the labels on a tape?}
-
@node Using Multiple Tapes
@section Using Multiple Tapes
@UNREVISED
Often you might want to write a large archive, one larger than will fit
on the actual tape you are using. In such a case, you can run multiple
@command{tar} commands, but this can be inconvenient, particularly if you
-are using options like @value{op-exclude} or dumping entire filesystems.
+are using options like @value{op-exclude} or dumping entire file systems.
Therefore, @command{tar} supports multiple tapes automatically.
Use @value{op-multi-volume} on the command line, and then @command{tar} will,
@menu
* Multi-Volume Archives:: Archives Longer than One Tape or Disk
* Tape Files:: Tape Files
+* Tarcat:: Concatenate Volumes into a Single Archive
+
@end menu
@node Multi-Volume Archives
that volume), use @value{op-extract}, again without
@value{op-multi-volume}.
-If an archive member is split across volumes (ie. its entry begins on
+If an archive member is split across volumes (ie. its entry begins on
one volume of the media and ends on another), you need to specify
@value{op-multi-volume} to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
@FIXME{example}
@FIXME{There should be a sample program here, including an exit
-before end. Is the exit status even checked in tar? :-(}
+before end. Is the exit status even checked in tar? :-(}
-@table @kbd
+@table @option
@item --multi-volume
@itemx -M
Creates a multi-volume archive, when used in conjunction with
or such, for pushing a common date in all volumes or an archive set.
+@node Tarcat
+@subsection Concatenate Volumes into a Single Archive
+
+@pindex tarcat
+ Sometimes it is necessary to convert existing @GNUTAR{} multi-volume
+archive to a single @command{tar} archive. Simply concatenating all
+volumes into one will not work, since each volume carries an additional
+information at the beginning. @GNUTAR{} is shipped with the shell
+script @command{tarcat} designed for this purpose.
+
+ The script takes a list of files comprising a multi-volume archive
+and creates the resulting archive at the standard output. For example:
+
+@smallexample
+@kbd{tarcat vol.1 vol.2 vol.3 | tar tf -}
+@end smallexample
+
+ The script implements a simple heuristics to determine the format of
+the first volume file and to decide how to process the rest of the
+files. However, it makes no attempt to verify whether the files are
+given in order or even if they are valid @command{tar} archives.
+It uses @command{dd} and does not filter its standard error, so you
+will usually see lots of spurious messages.
+
+@FIXME{The script is not installed. Should we install it?}
+
@node label
@section Including a Label in the Archive
@cindex Labeling an archive
@cindex Labels on the archive media
@UNREVISED
-@table @kbd
-@item -V @var{name}
-@itemx --label=@var{name}
-Create archive with volume name @var{name}.
-@end table
-
-This option causes @command{tar} to write out a @dfn{volume header} at
-the beginning of the archive. If @value{op-multi-volume} is used, each
-volume of the archive will have a volume header of @samp{@var{name}
-Volume @var{n}}, where @var{n} is 1 for the first volume, 2 for the
-next, and so on.
-
-@FIXME{Should the arg to --label be a quoted string?? No.}
-
-To avoid problems caused by misplaced paper labels on the archive
+@cindex @option{--label} option introduced
+@cindex @option{-V} option introduced
+ To avoid problems caused by misplaced paper labels on the archive
media, you can include a @dfn{label} entry---an archive member which
contains the name of the archive---in the archive itself. Use the
@value{op-label} option in conjunction with the @value{op-create} operation
to include a label entry in the archive as it is being created.
-If you create an archive using both @value{op-label} and
+@table @option
+@item --label=@var{archive-label}
+@itemx -V @var{archive-label}
+Includes an @dfn{archive-label} at the beginning of the archive when
+the archive is being created, when used in conjunction with the
+@value{op-create} operation. Checks to make sure the archive label
+matches the one specified (when used in conjunction with any other
+operation.
+@end table
+
+ If you create an archive using both @value{op-label} and
@value{op-multi-volume}, each volume of the archive will have an
archive label of the form @samp{@var{archive-label} Volume @var{n}},
where @var{n} is 1 for the first volume, 2 for the next, and so on.
@FIXME-xref{Multi-Volume Archives, for information on creating multiple
volume archives.}
-If you list or extract an archive using @value{op-label}, @command{tar} will
-print an error if the archive label doesn't match the @var{archive-label}
-specified, and will then not list nor extract the archive. In those cases,
-@var{archive-label} argument is interpreted as a globbing-style pattern
-which must match the actual magnetic volume label. @xref{exclude}, for
-a precise description of how match is attempted@footnote{Previous versions
-of @command{tar} used full regular expression matching, or before that, only
-exact string matching, instead of wildcard matchers. We decided for the
-sake of simplicity to use a uniform matching device through @command{tar}.}.
-If the switch @value{op-multi-volume} is being used, the volume label
-matcher will also suffix @var{archive-label} by @w{@samp{ Volume [1-9]*}}
-if the initial match fails, before giving up. Since the volume numbering
-is automatically added in labels at creation time, it sounded logical to
-equally help the user taking care of it when the archive is being read.
-
-The @value{op-label} was once called @option{--volume}, but is not available
-under that name anymore.
-
-To find out an archive's label entry (or to find out if an archive has
-a label at all), use @samp{tar --list --verbose}. @command{tar} will
-print the label first, and then print archive member information, as
-in the example below:
+@cindex Volume label, listing
+@cindex Listing volume label
+ The volume label will be displayed by @option{--list} along with
+the file contents. If verbose display is requested, it will also be
+explicitely marked as in the example below:
@smallexample
+@group
$ @kbd{tar --verbose --list --file=iamanarchive}
V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
-rw-rw-rw- ringo user 40 1990-05-21 13:30 iamafilename
+@end group
@end smallexample
-@table @kbd
-@item --label=@var{archive-label}
-@itemx -V @var{archive-label}
-Includes an @dfn{archive-label} at the beginning of the archive when
-the archive is being created, when used in conjunction with the
-@value{op-create} option. Checks to make sure the archive label
-matches the one specified (when used in conjunction with the
-@value{op-extract} option.
-@end table
+@cindex @option{--test-label} option introduced
+@anchor{--test-label option}
+ However, @option{--list} option will cause listing entire
+contents of the archive, which may be undesirable (for example, if the
+archive is stored on a tape). You can request checking only the volume
+by specifying @option{--test-label} option. This option reads only the
+first block of an archive, so it can be used with slow storage
+devices. For example:
+
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive}
+iamalabel
+@end group
+@end smallexample
+
+ If @option{--test-label} is used with a single command line
+argument, @command{tar} compares the volume label with the
+argument. It exits with code 0 if the two strings match, and with code
+2 otherwise. In this case no output is displayed. For example:
-To get a common information on all tapes of a series, use the
-@value{op-label} option. For having this information different in each
+@smallexample
+@group
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable'}
+@result{} 0
+$ @kbd{tar --test-label --file=iamanarchive 'iamalable' alabel}
+@result{} 1
+@end group
+@end smallexample
+
+ If you request any operation, other than @option{--create}, along
+with using @option{--label} option, @command{tar} will first check if
+the archive label matches the one specified and will refuse to proceed
+if it does not. Use this as a safety precaution to avoid accidentally
+overwriting existing archives. For example, if you wish to add files
+to @file{archive}, presumably labelled with string @samp{My volume},
+you will get:
+
+@smallexample
+@group
+$ @kbd{tar -rf archive --label 'My volume' .}
+tar: Archive not labeled to match `My volume'
+@end group
+@end smallexample
+
+@noindent
+in case its label does not match. This will work even if
+@file{archive} is not labelled at all.
+
+ Similarly, @command{tar} will refuse to list or extract the
+archive if its label doesn't match the @var{archive-label}
+specified. In those cases, @var{archive-label} argument is interpreted
+as a globbing-style pattern which must match the actual magnetic
+volume label. @xref{exclude}, for a precise description of how match
+is attempted@footnote{Previous versions of @command{tar} used full
+regular expression matching, or before that, only exact string
+matching, instead of wildcard matchers. We decided for the sake of
+simplicity to use a uniform matching device through
+@command{tar}.}. If the switch @value{op-multi-volume} is being used,
+the volume label matcher will also suffix @var{archive-label} by
+@w{@samp{ Volume [1-9]*}} if the initial match fails, before giving
+up. Since the volume numbering is automatically added in labels at
+creation time, it sounded logical to equally help the user taking care
+of it when the archive is being read.
+
+ The @value{op-label} was once called @option{--volume}, but is not available
+under that name anymore.
+
+ You can also use @option{--label} to get a common information on
+all tapes of a series. For having this information different in each
series created through a single script used on a regular basis, just
manage to get some date string as part of the label. For example:
@smallexample
+@group
$ @kbd{tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"}
$ @kbd{tar --create --file=/dev/tape --multi-volume \
--volume="Daily backup for `date +%Y-%m-%d`"}
+@end group
@end smallexample
-Also note that each label has its own date and time, which corresponds
+ Also note that each label has its own date and time, which corresponds
to when @GNUTAR{} initially attempted to write it,
often soon after the operator launches @command{tar} or types the
carriage return telling that the next tape is ready. Comparing date
rewinding tapes and the operator switching them were negligible, which
is usually not the case.
-@FIXME{was --volume}
-
@node verify
@section Verifying Data as It is Stored
@cindex Verifying a write operation
@cindex Double-checking a write operation
-@table @kbd
+@table @option
@item -W
@itemx --verify
Attempt to verify the archive after writing.
@appendix Genfile
@include genfile.texi
+@node Snapshot Files
+@appendix Format of the Incremental Snapshot Files
+@include snapshot.texi
+
@node Copying This Manual
@appendix Copying This Manual
projects / chaz / tar / blobdiff