tar: Using Multiple Tapes
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1 9.6 Using Multiple Tapes
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1 Often you might want to write a large archive, one larger than will fit
1 on the actual tape you are using. In such a case, you can run multiple
1 'tar' commands, but this can be inconvenient, particularly if you are
1 using options like '--exclude=PATTERN' or dumping entire file systems.
1 Therefore, 'tar' provides a special mode for creating multi-volume
1 archives.
1
1 "Multi-volume" archive is a single 'tar' archive, stored on several
1 media volumes of fixed size. Although in this section we will often
1 call 'volume' a "tape", there is absolutely no requirement for
1 multi-volume archives to be stored on tapes. Instead, they can use
1 whatever media type the user finds convenient, they can even be located
1 on files.
1
1 When creating a multi-volume archive, GNU 'tar' continues to fill
1 current volume until it runs out of space, then it switches to next
1 volume (usually the operator is queried to replace the tape on this
1 point), and continues working on the new volume. This operation
1 continues until all requested files are dumped. If GNU 'tar' detects
1 end of media while dumping a file, such a file is archived in split
1 form. Some very big files can even be split across several volumes.
1
1 Each volume is itself a valid GNU 'tar' archive, so it can be read
1 without any special options. Consequently any file member residing
1 entirely on one volume can be extracted or otherwise operated upon
1 without needing the other volume. Sure enough, to extract a split
1 member you would need all volumes its parts reside on.
1
1 Multi-volume archives suffer from several limitations. In
1 particular, they cannot be compressed.
1
1 GNU 'tar' is able to create multi-volume archives of two formats
1 (⇒Formats): 'GNU' and 'POSIX'.
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