tar: Backup Levels
1
1 5.3 Levels of Backups
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1
1 An archive containing all the files in the file system is called a "full
1 backup" or "full dump". You could insure your data by creating a full
1 dump every day. This strategy, however, would waste a substantial
1 amount of archive media and user time, as unchanged files are daily
1 re-archived.
1
1 It is more efficient to do a full dump only occasionally. To back up
1 files between full dumps, you can use "incremental dumps". A "level
1 one" dump archives all the files that have changed since the last full
1 dump.
1
1 A typical dump strategy would be to perform a full dump once a week,
1 and a level one dump once a day. This means some versions of files will
1 in fact be archived more than once, but this dump strategy makes it
1 possible to restore a file system to within one day of accuracy by only
1 extracting two archives--the last weekly (full) dump and the last daily
1 (level one) dump. The only information lost would be in files changed
1 or created since the last daily backup. (Doing dumps more than once a
1 day is usually not worth the trouble.)
1
1 GNU 'tar' comes with scripts you can use to do full and level-one
1 (actually, even level-two and so on) dumps. Using scripts (shell
1 programs) to perform backups and restoration is a convenient and
1 reliable alternative to typing out file name lists and 'tar' commands by
1 hand.
1
1 Before you use these scripts, you need to edit the file
1 'backup-specs', which specifies parameters used by the backup scripts
1 and by the restore script. This file is usually located in
1 '/etc/backup' directory. ⇒Backup Parameters, for its detailed
1 description. Once the backup parameters are set, you can perform
1 backups or restoration by running the appropriate script.
1
1 The name of the backup script is 'backup'. The name of the restore
1 script is 'restore'. The following sections describe their use in
1 detail.
1
1 _Please Note:_ The backup and restoration scripts are designed to be
1 used together. While it is possible to restore files by hand from an
1 archive which was created using a backup script, and to create an
1 archive by hand which could then be extracted using the restore script,
1 it is easier to use the scripts. ⇒Incremental Dumps, before
1 making such an attempt.
1