PERIODIC-SNAPSHOT(8) BSD System Manager's Manual PERIODIC-SNAPSHOT(8)NAMEperiodic-snapshot — run periodic UFS/ZFS backup snapshot maintenance task
SYNOPSISperiodic-snapshotDESCRIPTION
The periodic-snapshot utility is intended to be called by cron(8) to cre‐
ate 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 avail‐
able.
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 snap‐
shots 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 ALSOsh(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⟩
BSD September 03, 2004 BSD
