To create an archive that is larger than will fit on a single unit of
the media, use the --multi-volume (-M) option in conjunction with
the --create option (see create). A multi-volume
archive can be manipulated like any other archive (provided the
--multi-volume option is specified), but is stored on more
than one tape or disk.
When you specify --multi-volume, tar does not report an
error when it comes to the end of an archive volume (when reading), or
the end of the media (when writing). Instead, it prompts you to load
a new storage volume. If the archive is on a magnetic tape, you
should change tapes when you see the prompt; if the archive is on a
floppy disk, you should change disks; etc.
You can read each individual volume of a multi-volume archive as if it
were an archive by itself. For example, to list the contents of one
volume, use --list, without --multi-volume specified.
To extract an archive member from one volume (assuming it is described
that volume), use --extract, again without
--multi-volume.
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
--multi-volume to extract it successfully. In this case, you
should load the volume where the archive member starts, and use
‘tar --extract --multi-volume’—tar will prompt for later
volumes as it needs them. See extracting archives, for more
information about extracting archives.
--info-script=script-name
(--new-volume-script=script-name, -F
script-name) (see info-script) is like
--multi-volume (-M), except that tar does
not prompt you directly to change media volumes when a volume is
full—instead, tar runs commands you have stored in
script-name. For example, this option can be used to eject
cassettes, or to broadcast messages such as ‘Someone please come
change my tape’ when performing unattended backups. When
script-name is done, tar will assume that the media
has been changed.
Multi-volume archives can be modified like any other archive. To add
files to a multi-volume archive, you need to only mount the last
volume of the archive media (and new volumes, if needed). For all
other operations, you need to use the entire archive.
If a multi-volume archive was labeled using
--label=archive-label (-V archive-label)
(see label) when it was created, tar will not
automatically label volumes which are added later. To label
subsequent volumes, specify --label=archive-label again
in conjunction with the --append, --update or
--concatenate operation.
--multi-volume
-M
Creates a multi-volume archive, when used in conjunction with
--create (-c). To perform any other operation on a multi-volume
archive, specify --multi-volume in conjunction with that
operation.
--info-script=program-file
--new-volume-script=program-file
-F program-file
Creates a multi-volume archive via a script. Used in conjunction with
--create (-c). See info-script, dor a detailed discussion.
Beware that there is no real standard about the proper way, for
a tar archive, to span volume boundaries. If you have a
multi-volume created by some vendor's tar, there is almost
no chance you could read all the volumes with GNU tar.
The converse is also true: you may not expect
multi-volume archives created by GNU tar to be
fully recovered by vendor's tar. Since there is little
chance that, in mixed system configurations, some vendor's
tar will work on another vendor's machine, and there is a
great chance that GNU tar will work on most of
them, your best bet is to install GNU tar on all
machines between which you know exchange of files is possible.
Published under the terms of the GNU General Public License
