tar: What tar Does
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1 1.3 What 'tar' Does
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1 The 'tar' program provides the ability to create 'tar' archives, as well
1 as various other kinds of manipulation. For example, you can use 'tar'
1 on previously created archives to extract files, to store additional
1 files, or to update or list files which were already stored.
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1 Initially, 'tar' archives were used to store files conveniently on
1 magnetic tape. The name 'tar' comes from this use; it stands for 't'ape
1 'ar'chiver. Despite the utility's name, 'tar' can direct its output to
1 available devices, files, or other programs (using pipes). 'tar' may
1 even access remote devices or files (as archives).
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1 You can use 'tar' archives in many ways. We want to stress a few of
1 them: storage, backup, and transportation.
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1 Storage
1 Often, 'tar' archives are used to store related files for
1 convenient file transfer over a network. For example, the GNU
1 Project distributes its software bundled into 'tar' archives, so
1 that all the files relating to a particular program (or set of
1 related programs) can be transferred as a single unit.
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1 A magnetic tape can store several files in sequence. However, the
1 tape has no names for these files; it only knows their relative
1 position on the tape. One way to store several files on one tape
1 and retain their names is by creating a 'tar' archive. Even when
1 the basic transfer mechanism can keep track of names, as FTP can,
1 the nuisance of handling multiple files, directories, and multiple
1 links makes 'tar' archives useful.
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1 Archive files are also used for long-term storage. You can think
1 of this as transportation from the present into the future. (It is
1 a science-fiction idiom that you can move through time as well as
1 in space; the idea here is that 'tar' can be used to move archives
1 in all dimensions, even time!)
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1 Backup
1 Because the archive created by 'tar' is capable of preserving file
1 information and directory structure, 'tar' is commonly used for
1 performing full and incremental backups of disks. A backup puts a
1 collection of files (possibly pertaining to many users and
1 projects) together on a disk or a tape. This guards against
1 accidental destruction of the information in those files. GNU
1 'tar' has special features that allow it to be used to make
1 incremental and full dumps of all the files in a file system.
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1 Transportation
1 You can create an archive on one system, transfer it to another
1 system, and extract the contents there. This allows you to
1 transport a group of files from one system to another.
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