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### 1.3 What `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 `t`ape `ar`chiver. 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).

You can use `tar` archives in many ways. We want to stress a few of them: storage, backup, and transportation.

Storage

  Often, `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!)

Backup

  Because the archive created by `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 file system.

Transportation

  You can create an archive on one system, transfer it to another system, and extract the contents there. This allows you to transport a group of files from one system to another.

Next: Naming tar Archives, Previous: Definitions, Up: Introduction [Contents][Index]