tar Does
The tar program provides the ability to create tar
archives, as well as various other kinds of manipulation. For example,
you can use tar on previously created archives to extract files,
to store additional files, or to update or list files which were already
stored.
Initially, tar archives were used to store files conveniently on
magnetic tape. The name `tar' comes from this use; it stands for
tape archiver. Despite the utility's name, tar can
direct its output to available devices, files, or other programs (using
pipes). tar may even access remote devices or files (as archives).
@FIXME{the following table entries need a bit of work..}
You can use tar archives in many ways. We want to stress a few
of them: storage, backup, and transportation.
tar archives are used to store related files for
convenient file transfer over a network. For example, the GNU Project
distributes its software bundled into tar archives, so that
all the files relating to a particular program (or set of related
programs) can be transferred as a single unit.
A magnetic tape can store several files in sequence. However, the tape
has no names for these files; it only knows their relative position on
the tape. One way to store several files on one tape and retain their
names is by creating a tar archive. Even when the basic transfer
mechanism can keep track of names, as FTP can, the nuisance of handling
multiple files, directories, and multiple links makes tar
archives useful.
Archive files are also used for long-term storage. You can think of
this as transportation from the present into the future. (It is a
science-fiction idiom that you can move through time as well as in
space; the idea here is that tar can be used to move archives in
all dimensions, even time!)
tar is capable of preserving file
information and directory structure, tar is commonly used for
performing full and incremental backups of disks. A backup puts a
collection of files (possibly pertaining to many users and
projects) together on a disk or a tape. This guards against accidental
destruction of the information in those files. GNU tar has
special features that allow it to be used to make incremental and full
dumps of all the files in a filesystem.
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