tar: Backup Levels

1 
1 5.3 Levels of Backups
1 =====================
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