Utility script for maintaining rolling snapshots of ZFS datasets on FreeBSD 9.1.

snapzfs.sh

#!/bin/sh

# snapzfs.sh - Maintain rotating ZFS dataset snapshots
#
# Creates, rotates, and prunes rolling snapshots of ZFS datasets.  When
# this script is run, the sets defined in the configuration section below
# are snapshot and rotated as necessary depending on the age and number of
# existing snapshots.  Written for and tested on FreeBSD 9.1.
#
# Mark Shroyer
# Wed Feb 27 10:39:33 EST 2013

### BEGIN CONFIGURATION ###################################################

## Snapshot set definitions
snapshot_sets='swteam'

# Software team document share
swteam_pool='data'
swteam_dataset='swteam'
swteam_mount='/data/swteam'
swteam_keep_days=7
swteam_keep_weeks=4
swteam_keep_months=6

### END CONFIGURATION #####################################################

alias zfs=/sbin/zfs

get_mtime()
{
    stat -f %Sm -t $1 $2
}

snapshot_name()
{
    local class="$1"
    local number="$2"
    printf "%s.%03d" "$class" "$number"
}

create_snapshot()
{
    local pool="$1"
    local dataset="$2"
    local mount="$3"
    local class="$4"
    local retention="$5"

    echo "=> Deleting expired ${class} snapshots..."
    local index_max=$(( $retention - 1))
    local index_cur=$index_max
    local snapshot_cur=`snapshot_name ${class} ${index_cur}`
    while [ -e "${mount}/.zfs/snapshot/${snapshot_cur}" ]; do
        echo "${mount}/${snapshot_cur}"
        zfs destroy "${pool}/${dataset}@${snapshot_cur}"
        index_cur=$(( $index_cur + 1 ))
        snapshot_cur=`snapshot_name ${class} ${index_cur}`
    done

    echo "=> Rotating ${class} snapshots..."
    local index_new=$index_max
    local index_old=
    while [ $index_new -gt 0 ]; do
        index_old=$(( $index_new - 1))

        local name_old=`snapshot_name ${class} ${index_old}`
        local name_new=`snapshot_name ${class} ${index_new}`

        if [ -e "${mount}/.zfs/snapshot/${name_old}" ]; then
            zfs rename "${pool}/${dataset}@${name_old}" \
                "${pool}/${dataset}@${name_new}"
        fi

        index_new=$index_old
    done

    echo "=> Creating new ${class} snapshot..."
    local snapshot_first=`snapshot_name ${class} 0`
    zfs snapshot "${pool}/${dataset}@${snapshot_first}"
}

check_snapshot()
{
    local pool="$1"
    local dataset="$2"
    local mount="$3"
    local class="$4"
    local retention="$5"
    local format="$6"

    if [ -z "$retention" ] || [ "$retention" -eq 0 ]; then
        # Don't need a snapshot
        return 1
    fi

    local snapshot_path="${mount}/.zfs/snapshot/`snapshot_name ${class} 0`"
    if [ ! -e "${snapshot_path}" ]; then
        # Time for a new snapshot
        return 0
    fi

    local date_current=`date +${format}`
    local date_snapshot=`get_mtime ${format} ${snapshot_path}`
    if [ $date_current -gt $date_snapshot ]; then
        # Time for a new snapshot
        return 0
    else
        # No new snapshot in this class required
        return 1
    fi
}

for set_name in `echo $snapshot_sets`; do
    set_pool=`eval "echo \\\$\${set_name}_pool"`
    set_dataset=`eval "echo \\\$\${set_name}_dataset"`
    set_mount=`eval "echo \\\$\${set_name}_mount"`
    set_keep_days=`eval "echo \\\$\${set_name}_keep_days"`
    set_keep_weeks=`eval "echo \\\$\${set_name}_keep_weeks"`
    set_keep_months=`eval "echo \\\$\${set_name}_keep_months"`

    # So that future date comparisons against the snapshot's mtime will
    # work as expected...
    touch "${set_mount}"

    check_snapshot "$set_pool" "$set_dataset" "$set_mount" \
        daily "$set_keep_days" %Y%j
    if [ $? -eq 0 ]; then
        create_snapshot "$set_pool" "$set_dataset" "$set_mount" \
            daily "$set_keep_days"
    fi

    check_snapshot "$set_pool" "$set_dataset" "$set_mount" \
        weekly "$set_keep_weeks" %Y%U
    if [ $? -eq 0 ]; then
        create_snapshot "$set_pool" "$set_dataset" "$set_mount" \
            weekly "$set_keep_weeks"
    fi

    check_snapshot "$set_pool" "$set_dataset" "$set_mount" \
        monthly "$set_keep_months" %Y%m
    if [ $? -eq 0 ]; then
        create_snapshot "$set_pool" "$set_dataset" "$set_mount" \
            monthly "$set_keep_months"
    fi
done