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(tar.info)Backup Levels

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Levels of Backups
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   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 a incremental dump.  A "level one"
dump archives all the files that have changed since the last full dump.

   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
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.  Once the backup parameters are set, you can
perform backups or restoration by running the appropriate script.

   The name of the restore script is `restore'.  The names of the level
one and full backup scripts are, respectively, `level-1' and `level-0'.
The `level-0' script also exists under the name `weekly', and the
`level-1' under the name `daily'--these additional names can be changed
according to your backup schedule.

   _Please Note:_ The backup scripts and the 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.  Note: Inc Dumps,
and Note: Inc Dumps, before making such an attempt.