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Man Pages


Manual Reference Pages  -  PERIODIC-SNAPSHOT (8)

NAME

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

CONTENTS

Synopsis
Description
Files
Examples
See Also
History
Authors

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/">http://people.freebsd.org/~rse/snapshot/.

HISTORY

The periodic-snapshot utility first appeared in
.Fx .

AUTHORS


.An Ralf S. Engelschall Aq rse@FreeBSD.org
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