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9.6.1 Archives Longer than One Tape or Disk

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 Design by Interspire