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Automatic ZFS Snapshot Rotation on FreeBSD

11 comments

OpenSolaris has ZFS Automatic Snapshots; FreeBSD, while it has ZFS, doesn’t have a comparable feature that I’m aware of. So I wrote my own, zfs-snapshot.sh:

#!/usr/local/bin/bash

# Path to ZFS executable:
ZFS=/sbin/zfs

# Parse arguments:
TARGET=$1
SNAP=$2
COUNT=$3

# Function to display usage:
usage() {
    scriptname=`/usr/bin/basename $0`
    echo "$scriptname: Take and rotate snapshots on a ZFS file system"
    echo
    echo "  Usage:"
    echo "  $scriptname target snap_name count"
    echo
    echo "  target:    ZFS file system to act on"
    echo "  snap_name: Base name for snapshots, to be followed by a '.' and"
    echo "             an integer indicating relative age of the snapshot"
    echo "  count:     Number of snapshots in the snap_name.number format to"
    echo "             keep at one time.  Newest snapshot ends in '.0'."
    echo
    exit
}

# Basic argument checks:
if [ -z $COUNT ] ; then
    usage
fi

if [ ! -z $4 ] ; then
    usage
fi

# Snapshots are number starting at 0; $max_snap is the highest numbered
# snapshot that will be kept.
max_snap=$(($COUNT -1))

# Clean up oldest snapshot:
if [ -d /${TARGET}/.zfs/snapshot/${SNAP}.${max_snap} ] ; then
    $ZFS destroy -r ${TARGET}@${SNAP}.${max_snap}
fi

# Rename existing snapshots:
dest=$max_snap
while [ $dest -gt 0 ] ; do
    src=$(($dest - 1))
    if [ -d /${TARGET}/.zfs/snapshot/${SNAP}.${src} ] ; then
	$ZFS rename -r ${TARGET}@${SNAP}.${src} ${TARGET}@${SNAP}.${dest}
    fi
    dest=$(($dest - 1))
done

# Create new snapshot:
$ZFS snapshot -r ${TARGET}@${SNAP}.0

From the command line, call the script something like the following:

./zfs-snapshot.sh tank weekly 5

This would take a recursive snapshot of the “tank” zpool with the basename weekly, rotating through five snapshots with names “weekly.0″ through “weekly.4″. This allows you to implement a snapshot scheme approximately similar to NetApp’s hourly-daily-weekly scheme, if you like. Because my FreeBSD workstation isn’t on 24×7, I run hourly snapshots out of /etc/crontab:

# Automated ZFS backups (hourly):
0 * * * * root /root/bin/zfs-snapshot.sh tank hourly 25

And daily/weekly/monthly snapshots out of /usr/local/etc/anacrontab (from the sysutils/anacron port):

PATH=/bin:/sbin:/usr/bin:/usr/sbin

# days		make sure the command is executed at least every 'days' days
# delay		delay in minutes, before a command starts
# id		unique id of a command

# days	delay	id		command
1	5	daily		periodic daily
1	10	daily_snap	/root/bin/zfs-snapshot.sh tank daily 8
7	15	weekly		periodic weekly
7	30	weekly_snap	/root/bin/zfs-snapshot.sh tank weekly 5
30	60	monthly		periodic monthly
30	90	monthly_snap	/root/bin/zfs-snapshot.sh tank monthly 13

(Of course, this isn’t as cool as the Gnome-integrated Time Slider in OpenSolaris, but it scratches my itch sufficiently.)

Written by Andy

April 7th, 2010 at 7:59 pm

Posted in freebsd

Tagged with , , , ,

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11 Responses to 'Automatic ZFS Snapshot Rotation on FreeBSD'

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  1. Thanks for this script!
    But, can You make change this script to:
    script creates a snapshot of the real date/time?
    Like tank@12:00:00-01-31-11

    Best Regards.

    P.s.
    Sorry for my English :)

    Desper

    10 Jan 11 at 1:23 pm

  2. @Desper – The challenge there would be associating a particular time stamp with the type of snapshot. Would you require that your dailies/weeklies/monthlies always run at the same time of day and determine your snapshot type from that? Or would you add a prefix or change the naming convention for the non-hourlies?

    (One nice thing about the time stamp is that you could eliminate the zfs rename portion of the script.)

    Andy

    13 Jan 11 at 11:00 am

  3. [...] http://andyleonard.com/2010/04/07/automatic-zfs-snapshot-rotation-on-freebsd/ Amplify’d from andyleonard.com [...]

    飄狂山莊 | [引用]zfs snapshot script

    10 Mar 11 at 11:02 am

  4. Hi there,

    Am running FreeBSD 8.2 with the v28 pool patch, i think something must have changed in the command syntax – i vaguely remember this when i was running OpenSolaris that zfs list changed…

    cannot create snapshot ‘tank/vol0/users@hourly.0′: dataset already exists
    no snapshots were created

    Looks like the rename is not working, will investigate further…

    iMx

    20 Mar 11 at 6:59 am

  5. Ah ha, its this bit:

    # Clean up oldest snapshot:
    if [ -d /${TARGET}/.zfs/snapshot/${SNAP}.${max_snap} ] ; then
    $ZFS destroy -r ${TARGET}@${SNAP}.${max_snap}
    fi

    its because i have the zfs mounted differently from the zpool name:

    ie tank/vol0/users@hourly.0

    is mounted as /vol0/users

    iMx

    20 Mar 11 at 7:02 am

  6. Thanks for your script! I did a small change to use the real mount point with:

    TARGET_MOUNT=$($ZFS get -H -o value mountpoint $TARGET)

    I put a copy on my own blog http://hype-o-thetic.com/2011/03/22/andyleonard-com-zfs-snapshot-sh/

    gimpe

    22 Mar 11 at 6:19 pm

  7. Thanks for the nice script!

    I made it compatible with zfs-fuse which doesn’t have .zfs directories:
    https://gist.github.com/1087896

    Ertug Karamatli

    17 Jul 11 at 10:30 am

  8. @Ertug – Thanks – and interesting timing. I had just written almost the same thing to work around FreeBSD’s kern/156781 bug (the .zfs/snapshot directory stops working).

    Andy

    18 Jul 11 at 11:51 am

  9. @Ertug – Thanks! the current version of zfsonlinux also lacks the .zfs directory. You just saved me a lot of time.

    Aaron

    7 Feb 12 at 7:27 am

  10. I’m setting this up now on my home server, it looks like exactly what I was after. Many thanks for your efforts!

    sim

    12 Apr 12 at 2:16 pm

  11. Great script and documentation — thanks for all of the time you saved me. Nice to see someone giving back with some KISS code/documentation.

    John

    23 Apr 12 at 4:14 pm

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