Archives Longer than One Tape or Disk
*(This message will disappear, once this node revised.)*
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' (`-c') option (Note: create.). A "multi-volume"
archive can be manipulated like any other archive (provided the
`--multi-volume' (`-M') option is specified), but is stored on more
than one tape or disk.
When you specify `--multi-volume' (`-M'), `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' (`-t'), without `--multi-volume' (`-M') specified.
To extract an archive member from one volume (assuming it is described
that volume), use `--extract' (`--get', `-x'), again without
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' (`-M') 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. Note: extracting archives, for more information about
`--info-script=SCRIPT-NAME' (`--new-volume-script=SCRIPT-NAME', `-F
SCRIPT-NAME') 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') (Note: label.) when it was created, `tar' will
not automatically label volumes which are added later. To label
subsequent volumes, specify `--label=ARCHIVE-LABEL' (`-V
ARCHIVE-LABEL') again in conjunction with the `--append' (`-r'),
`--update' (`-u') or `--concatenate' (`--catenate', `-A') operation.
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' (`-M') in
conjunction with that operation.
Creates a multi-volume archive via a script. Used in conjunction
with `--create' (`-c').
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.
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