EXPIRE_BACKUPS(1)						       S3QL							 EXPIRE_BACKUPS(1)

NAME

       expire_backups - Intelligently expire old backups

SYNOPSIS

       expire_backups [options] <age> [<age> ...]

DESCRIPTION

       The expire_backups command intelligently remove old backups that are no longer needed.

       To define what backups you want to keep for how long, you define a number of age ranges. expire_backups ensures that you will have at least
       one backup in each age range at all times. It will keep exactly as many backups as are required for that and delete any backups that become
       redundant.

       Age  ranges  are specified by giving a list of range boundaries in terms of backup cycles. Every time you create a new backup, the existing
       backups age by one cycle.

       Example: when expire_backups is called with the age range definition 1 3 7 14 31, it will guarantee that  you  always  have  the  following
       backups available:

       1. A backup that is 0 to 1 cycles old (i.e, the most recent backup)

       2. A backup that is 1 to 3 cycles old

       3. A backup that is 3 to 7 cycles old

       4. A backup that is 7 to 14 cycles old

       5. A backup that is 14 to 31 cycles old

       Note   If  you do backups in fixed intervals, then one cycle will be equivalent to the backup interval. The advantage of specifying the age
	      ranges in terms of backup cycles rather than days or weeks is that it allows you to gracefully handle  irregular	backup	intervals.
	      Imagine  that  for some reason you do not turn on your computer for one month. Now all your backups are at least a month old, and if
	      you had specified the above backup strategy in terms of absolute ages, they would all be deleted! Specifying age ranges in terms	of
	      backup cycles avoids these sort of problems.

       expire_backups usage is simple. It requires backups to have names of the forms year-month-day_hour:minute:seconds (YYYY-MM-DD_HH:mm:ss) and
       works on all backups in the current directory. So for the above backup strategy, the correct invocation would be:

       expire_backups.py 1 3 7 14 31

       When storing your backups on an S3QL file system, you probably want to specify the --use-s3qlrm option as well. This  tells  expire_backups
       to use the s3qlrm command to delete directories.

       expire_backups  uses  a "state file" to keep track which backups are how many cycles old (since this cannot be inferred from the dates con-
       tained in the directory names). The standard name for this state file is  .expire_backups.dat.  If  this  file  gets  damaged  or  deleted,
       expire_backups  no longer knows the ages of the backups and refuses to work. In this case you can use the --reconstruct-state option to try
       to reconstruct the state from the backup dates. However, the accuracy of this reconstruction depends strongly on how rigorous you have been
       with making backups (it is only completely correct if the time between subsequent backups has always been exactly the same), so it's gener-
       ally a good idea not to tamper with the state file.

OPTIONS

       The expire_backups command accepts the following options:

	  --quiet
		 be really quiet

	  --debug
		 activate debugging output

	  --version
		 just print program version and exit

	  --state <file>
		 File to save state information in (default: ".expire_backups.dat")

	  -n	 Dry run. Just show which backups would be deleted.

	  --reconstruct-state
		 Try to reconstruct a missing state file from backup dates.

	  --use-s3qlrm
		 Use s3qlrm command to delete backups.

EXIT STATUS

       expire_backups returns exit code 0 if the operation succeeded and 1 if some error occured.

SEE ALSO

       expire_backups is shipped as part of S3QL, http://code.google.com/p/s3ql/.

COPYRIGHT

       2008-2011, Nikolaus Rath

1.11.1								  August 27, 2014						 EXPIRE_BACKUPS(1)