An archive containing all the files in the file system is called a
full backup or full dump. You could insure your data by
creating a full dump every day. This strategy, however, would waste a
substantial amount of archive media and user time, as unchanged files
are daily re-archived.
It is more efficient to do a full dump only occasionally. To back up
files between full dumps, you can use incremental dumps. A level
one dump archives all the files that have changed since the last full
A typical dump strategy would be to perform a full dump once a week,
and a level one dump once a day. This means some versions of files
will in fact be archived more than once, but this dump strategy makes
it possible to restore a file system to within one day of accuracy by
only extracting two archives—the last weekly (full) dump and the
last daily (level one) dump. The only information lost would be in
files changed or created since the last daily backup. (Doing dumps
more than once a day is usually not worth the trouble).
GNU tar comes with scripts you can use to do full
and level-one (actually, even level-two and so on) dumps. Using
scripts (shell programs) to perform backups and restoration is a
convenient and reliable alternative to typing out file name lists
and tar commands by hand.
Before you use these scripts, you need to edit the file
backup-specs, which specifies parameters used by the backup
scripts and by the restore script. This file is usually located
in /etc/backup directory. See Backup Parameters, for its
detailed description. Once the backup parameters are set, you can
perform backups or restoration by running the appropriate script.
The name of the backup script is backup. The name of the
restore script is restore. The following sections describe
their use in detail.
Please Note: The backup and restoration scripts are
designed to be used together. While it is possible to restore files by
hand from an archive which was created using a backup script, and to create
an archive by hand which could then be extracted using the restore script,
it is easier to use the scripts. See Incremental Dumps, before
making such an attempt.
Published under the terms of the GNU General Public License