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GNU Extensions to the Archive Format
====================================

     _(This message will disappear, once this node revised.)_

   The GNU format uses additional file types to describe new types of
files in an archive.  These are listed below.

`GNUTYPE_DUMPDIR'
`'D''
     This represents a directory and a list of files created by the
     `--incremental' (`-G') option.  The `size' field gives the total
     size of the associated list of files.  Each file name is preceded
     by either a `Y' (the file should be in this archive) or an `N'.
     (The file is a directory, or is not stored in the archive.)  Each
     file name is terminated by a null.  There is an additional null
     after the last file name.

`GNUTYPE_MULTIVOL'
`'M''
     This represents a file continued from another volume of a
     multi-volume archive created with the `--multi-volume' (`-M')
     option.  The original type of the file is not given here.  The
     `size' field gives the maximum size of this piece of the file
     (assuming the volume does not end before the file is written out).
     The `offset' field gives the offset from the beginning of the
     file where this part of the file begins.  Thus `size' plus
     `offset' should equal the original size of the file.

`GNUTYPE_SPARSE'
`'S''
     This flag indicates that we are dealing with a sparse file.  Note
     that archiving a sparse file requires special operations to find
     holes in the file, which mark the positions of these holes, along
     with the number of bytes of data to be found after the hole.

`GNUTYPE_VOLHDR'
`'V''
     This file type is used to mark the volume header that was given
     with the `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') option when
     the archive was created.  The `name' field contains the `name'
     given after the `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL')
     option.  The `size' field is zero.  Only the first file in each
     volume of an archive should have this type.

   You may have trouble reading a GNU format archive on a non-GNU
system if the options `--incremental' (`-G'), `--multi-volume' (`-M'),
`--sparse' (`-S'), or `--label=ARCHIVE-LABEL' (`-V ARCHIVE-LABEL') were
used when writing the archive.  In general, if `tar' does not use the
GNU-added fields of the header, other versions of `tar' should be able
to read the archive.  Otherwise, the `tar' program will give an error,
the most likely one being a checksum error.