Including a Label in the Archive
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Create archive with volume name NAME.
This option causes `tar' to write out a "volume header" at the
beginning of the archive. If `--multi-volume' (`-M') is used, each
volume of the archive will have a volume header of `NAME Volume N',
where N is 1 for the first volume, 2 for the next, and so on.
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' (`-c') operation to include a label entry in the archive
as it is being created.
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. , for
information on creating multiple volume archives.
If you list or extract an archive using `--label=ARCHIVE-LABEL' (`-V
ARCHIVE-LABEL'), `tar' will print an error if the archive label doesn't
match the ARCHIVE-LABEL specified, and will then not list nor extract
the archive. In those cases, ARCHIVE-LABEL argument is interpreted as
a globbing-style pattern which must match the actual magnetic volume
label. Note: exclude, for a precise description of how match is
attempted(1). 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
The `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') was once called
`--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 `tar --list --verbose'. `tar' will print the
label first, and then print archive member information, as in the
$ 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
Includes an "archive-label" at the beginning of the archive when
the archive is being created, when used in conjunction with the
`--create' (`-c') option. Checks to make sure the archive label
matches the one specified (when used in conjunction with the
`--extract' (`--get', `-x') option.
To get a common information on all tapes of a series, use the
`--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') option. 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 ususally not the
---------- Footnotes ----------
(1) 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 `tar'.
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