tar is short for "tape archive", although its use with magnetic tape backups is primarily of historical concern. tar is both a command and a file format used by the command. It is used to collect several files into one archive, which can be more easily managed or compressed as a unit, often with gzip or bzip2.
Tar has several uses, but the most commonly used is to extract or to create tar archive (known as "tarballs")
To unpack a standard .tar file, use the command
tar -xvf filename
The Command options of tar:
- x: decompress something
- t: view contents
- v: verbose mode
- f: input from a file
(Note that, unlike most commands, the '-' before the options may be omitted.)
To create a tarball, you can use
tar cf tarballname.tar files
which can be compressed afterwards.
Decompressing tarballs that have been gzipped can be done in two ways: first decompressing then extracting, by
Alternatively, some versions of tar support inbuilt decompression of gzipped tar files. This requires the z option, transforming the command to:
tar -xvzf filename
Decompressing Bzip2 tar files can be done in the same manner, bunzip2 first and then tar, but some versions of tar allow you to use the j option:
tar -xvjf filename
If this option is not available to you, the same effect can be achieved by the following:
bunzip2 filename | tar -xvf -
where, as mentioned above, the output of bunzip2 is piped to tar, which is directed to read from stdin with the final '-'.
View contents of an archive
If you just want to view the contents of a tar file instead of extracting it:
tar -tf filename
You can filter it through gzip or bunzip2 respectively:
tar -tzf filename tar -tjf filename
Using tar to copy files
In addition to archiving files, tar can also be used to copy a group of files and directories using a pipe. To move all the files (including hidden ones) in /olddir to /newdir, for example, the syntax is
tar -c . | (cd /newdir; tar -xv)
Don't worry about the -v option with the pipe; the -v option writes to the stderr stream and will not interfere with the pipe.
Using tar to transmit files
In addition to copying files, tar can also be used to transmit a group of files and directories using a pipe and ssh. To transmit all the files from your directory to the folder /archive on 192.168.0.80, for example, the syntax is
tar cv -f- . | ssh firstname.lastname@example.org "(mkdir /archive; cd /archive; tar -xv)"
See also: Cloning
Here's an example of including everything but opt and home directories.
tar --exclude=home --exclude=opt --exclude=srv -cvf slash.tar /
This excludes all opt and home directories, not just the ones under the current working directory.
Tar A Mounted Directory With No Leading Paths
tar -cvpjf /path/to/file.tar.bz2 ./*
This will tar any mounted directory and it will contain no nested path folders. This is helpful when you wish to back-up a mounted partition to a disk or another drive, and have the option of extracting it again without the usual leading paths.