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PERIODIC-SNAPSHOT(8)   DragonFly System Manager's Manual  PERIODIC-SNAPSHOT(8)


NAME

     periodic-snapshot - run periodic UFS/ZFS backup snapshot maintenance task


SYNOPSIS

     periodic-snapshot


DESCRIPTION

     The periodic-snapshot utility is intended to be called by cron(8) to
     create and expire UFS/ZFS backup snapshots through the snapshot(8)
     command according to the snapshot_enable and snapshot_schedule settings
     from periodic.conf(5).

     The system /etc/crontab will typically have entries for periodic-snapshot
     similar to the following example:

           # do hourly/daily/weekly maintenance of FreeBSD UFS/ZFS snapshots
           0  *  *  *  *  root  periodic-snapshot hourly
           0  0  *  *  *  root  periodic-snapshot daily
           0  0  *  *  0  root  periodic-snapshot weekly

     The /etc/defaults/periodic.conf system registry will typically contain
     the following defaults which keep periodic-snapshot disabled by default:

           snapshot_enable="NO"
           snapshot_schedule=""

     The snapshot_schedule variable values have to conform to the following
     grammar:

           <schedule>    ::= <entry>*
           <entry>       ::= <fs> ("," <fs>)* ":" <spec>
           <fs>          ::= /^.*$/
           <spec>        ::= <gen_weekly> ":" <gen_daily> ":" <gen_hourly>
           <gen_weekly>  ::= <generation>
           <gen_daily>   ::= <generation>
           <gen_hourly>  ::= <generation> ("@" <hour> ("," <hour>)*)?
           <generation>  ::= /^[0-9]+$/
           <hour>        ::= /^(0?[0-9]|1[0-9]|2[0-3])$/

     The number of all added "generation" numbers of a filesystem cannot be
     larger than 20 because this is the maximum number of snapshots which can
     be created on a UFS/ZFS filesystem. A "generation" number of "0" disables
     the creation of backup snapshots.

     The used schedule heavily depends on how much generations of snapshots
     should be kept, which in turn depends on how much disk space is
     available.


FILES

     /etc/crontab                     the periodic-snapshot utility is
                                      typically called via entries in the
                                      system default cron(8) table.

     /etc/defaults/periodic.conf      system registry containing variables
                                      that control the behaviour of
                                      periodic-snapshot.

     /etc/periodic.conf               this file contains local overrides for
                                      the default periodic-snapshot
                                      configuration.


EXAMPLES

     In order to configure UFS/ZFS backup snapshot creation, add lines to
     /etc/periodic.conf similar to:

           snapshot_enable="YES"
           snapshot_schedule="/,/usr:2:1:0 /var:0:2:4 /home:2:6:8@8,12,16,20"

     This schedules the following UFS/ZFS backup snapshots: 2 weekly
     (weekly.[01]) and 1 daily (daily.0) generation of snapshots on the / and
     /usr filesystems, two daily (daily.[01]) and 4 hourly (hourly.[0123])
     generations of snapshots on the /var filesystem, and 2 weekly
     (weekly.[01]), 6 daily (daily.[0123456]) and 8 hourly (hourly.[01234567])
     generations of snapshots on the /home filesystem.  While the hourly
     snapshots on /var are created every hour, the hourly snapshots on /home
     are created on 08:00, 12:00, 16:00 and 20:00 only.


SEE ALSO

     sh(1), crontab(5), periodic.conf(5), cron(8), snapshot(8),
     http://people.freebsd.org/~rse/snapshot/.


HISTORY

     The periodic-snapshot utility first appeared in FreeBSD.


AUTHORS

     Ralf S. Engelschall <rse@FreeBSD.org>

DragonFly 6.5-DEVELOPMENT      September 3, 2004     DragonFly 6.5-DEVELOPMENT

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