To avoid problems caused by misplaced paper labels on the archive
media, you can include a label entry—an archive member which
contains the name of the archive—in the archive itself. Use the
--label=archive-label (-V archive-label)
option in conjunction with the --create operation to include
a label entry in the archive as it is being created.
Includes an archive-label at the beginning of the archive when
the archive is being created, when used in conjunction with the
--create operation. Checks to make sure the archive label
matches the one specified (when used in conjunction with any other
If you create an archive using both
--label=archive-label (-V archive-label)
and --multi-volume (-M), each volume of the archive
will have an archive label of the form ‘archive-label
Volume n’, where n is 1 for the first volume, 2 for the
next, and so on. See Using Multiple Tapes, for information on
creating multiple volume archives.
The volume label will be displayed by --list along with
the file contents. If verbose display is requested, it will also be
explicitely marked as in the example below:
$ tar --verbose --list --file=iamanarchive
V--------- 0 0 0 1992-03-07 12:01 iamalabel--Volume Header--
-rw-r--r-- ringo user 40 1990-05-21 13:30 iamafilename
However, --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 --test-label option. This option reads only the
first block of an archive, so it can be used with slow storage
devices. For example:
$ tar --test-label --file=iamanarchive
If --test-label is used with a single command line
argument, 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:
$ tar --test-label --file=iamanarchive 'iamalable'
$ tar --test-label --file=iamanarchive 'iamalable' alabel
If you request any operation, other than --create, along
with using --label option, 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 archive, presumably labelled with string ‘My volume’,
you will get:
$ tar -rf archive --label 'My volume' .
tar: Archive not labeled to match `My volume'
in case its label does not match. This will work even if
archive is not labelled at all.
Similarly, tar will refuse to list or extract the
archive if its label doesn't match the archive-label
specified. In those cases, archive-label argument is interpreted
as a globbing-style pattern which must match the actual magnetic
volume label. See exclude, for a precise description of how match
is attempted1. If the switch --multi-volume (-M) is being used,
the volume label matcher will also suffix archive-label by
‘ 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 --label was once called --volume, but is not
available under that name anymore.
You can also use --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:
$ tar cfMV /dev/tape "Daily backup for `date +%Y-%m-%d`"
$ tar --create --file=/dev/tape --multi-volume \
--volume="Daily backup for `date +%Y-%m-%d`"
Also note that each label has its own date and time, which corresponds
to when GNU tar initially attempted to write it,
often soon after the operator launches tar or types the
carriage return telling that the next tape is ready. Comparing date
labels does give an idea of tape throughput only if the delays for
rewinding tapes and the operator switching them were negligible, which
is usually not the case.
 Previous versions of 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
Published under the terms of the GNU General Public License