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Chapter 11: Backing Up Data
tar Archives
The tar command creates an archive file from one or more specified files or directo-
ries. It can also list the contents of an archive, or extract files and directories from an
archive. A tar archive file is also known as a tarfile or a tarball.
A tar archive file offers several advantages over a directory of separate files. For
example, it makes sending a whole directory by email a lot easier. Directories con-
taining lots of similar files can be compressed more efficiently when the compression
operates on all the data in a single file.
A common use for a tar archive is to aid in the distribution of the source program
files for free or open source software. In most cases, the tar archives are compressed
with the gzip or bzip2 programs. However, if all the files being archived are already
compressed (which is usually true of audio, video, and OpenOffice.org files), com-
pressing the archive itself will not have much benefit.
You can name a tarred file anything you want, but certain file extensions are conven-
tionally used to tell recipients how to unpack the file. The most common extensions
are:
.tar
For uncompressed tar archives
.tar.gz or .tgz
For tar archives that have been compressed with the gzip compression program
.tar.bz2 or .tbz
For tar archives that have been compressed with the bzip2 compression program
The syntax of a tar command is:
tar options ...