Split Recovery (GNU tar 1.35)

#### 8.3.10.1 Extracting Members Split Between Volumes

If a member is split between several volumes of an old GNU format archive most third party `tar` implementation will fail to extract it. To extract it, use `tarcat` program (see Concatenate Volumes into a Single Archive). This program is available from GNU `tar` home page. It concatenates several archive volumes into a single valid archive. For example, if you have three volumes named from `vol-1.tar` to `vol-3.tar`, you can do the following to extract them using a third-party `tar`:

    $ tarcat vol-1.tar vol-2.tar vol-3.tar | tar xf -

You could use this approach for most (although not all) PAX format archives as well. However, extracting split members from a PAX archive is a much easier task, because PAX volumes are constructed in such a way that each part of a split member is extracted to a different file by `tar` implementations that are not aware of GNU extensions. More specifically, the very first part retains its original name, and all subsequent parts are named using the pattern:

    %d/GNUFileParts/%f.%n

where symbols preceded by ‘`%`’ are macro characters that have the following meaning:

Meta-character | Replaced By
--- | ---
%d | The directory name of the file, equivalent to the result of the `dirname` utility on its full name.
%f | The file name of the file, equivalent to the result of the `basename` utility on its full name.
%p | The process ID of the `tar` process that created the archive.
%n | Ordinal number of this particular part.

For example, if the file `var/longfile` was split during archive creation between three volumes, then the member names will be:

    var/longfile
    var/GNUFileParts/longfile.1
    var/GNUFileParts/longfile.2

When you extract your archive using a third-party `tar`, these files will be created on your disk, and the only thing you will need to do to restore your file in its original form is concatenate them in the proper order, for example:

    $ cd var
    $ cat GNUFileParts/longfile.1 \
      GNUFileParts/longfile.2 >> longfile
    $ rm -f GNUFileParts

Notice, that if the `tar` implementation you use supports PAX format archives, it will probably emit warnings about unknown keywords during extraction. They will look like this:

    Tar file too small
    Unknown extended header keyword 'GNU.volume.filename' ignored.
    Unknown extended header keyword 'GNU.volume.size' ignored.
    Unknown extended header keyword 'GNU.volume.offset' ignored.

You can safely ignore these warnings.

If your `tar` implementation is not PAX-aware, you will get more warnings and more files generated on your disk, e.g.:

    $ tar xf vol-1.tar
    var/PaxHeaders/longfile: Unknown file type 'x', extracted as
    normal file
    Unexpected EOF in archive
    $ tar xf vol-2.tar
    tmp/GlobalHead.1: Unknown file type 'g', extracted as normal file
    GNUFileParts/PaxHeaders/sparsefile.1: Unknown file type
    'x', extracted as normal file

Ignore these warnings. The `PaxHeaders.*` directories created will contain files with extended header keywords describing the extracted files. You can delete them, unless they describe sparse members. Read further to learn more about them.