This script will automatically take and mergeback VirtualBox snapshots to keep a rolling archive of a running machine. Call with, # ./vbox_auto_snapshots vm_name_1 [vm_name_n...]

vbox_auto_snapshots

#! /bin/bash

# This script will automatically take and mergeback VirtualBox snapshots to
# keep a rolling archive of a running machine.
# Call with, 
# ./vbox_auto_snapshots vm_name_1 [vm_name_n...]

# Define snapshot retention periods
KEEP_WEEKLY=4
KEEP_DAILY=6

# Day to take weekly 
#   Monday = 1
WEEK_ENDS=5

SNAP_LIST="$(mktemp /tmp/vbox_snaps.XXXXXXXXXX)"

function extractDate {
    # extract the date from a snapshot name
    # this is not smart, only send formatted names
    echo "$1" | sed -e 's#.*-[0-9]\{8\}-[0-9]\{6\}-\([0-9]\+\)\"*#\1#'
}

function extractName {
    echo "$1" | sed -e 's#.*="\('"$PREFIX"'[0-9-]*\)"#\1#'
}

function setSnaps {
    # populate a list of current snapshots for a machine
    VBoxManage showvminfo "$1"  --machinereadable | \
        grep "SnapshotName.*$PREFIX" > "$SNAP_LIST"
}

function getLastSnapDate {
    local _lastSnap=0
    setSnaps "$1"
    while read line; do
        local _newdate=`extractDate "$line"`
        if [ "$_newdate" -gt "$_lastSnap" ]
        then
            _lastSnap="$_newdate"
        fi
    done <  "$SNAP_LIST"
    echo $_lastSnap 
}

function getAge {
    expr $(date "+%s") - $1
}

function takeSnapshot {
    VBoxManage snapshot "$1" take "$PREFIX"-"$(date '+%Y%m%d-%H%M%S-%s')"
}

function deleteOldSnaps {
    setSnaps "$1"
    while read line; do
        local _age=`getAge "$(extractDate $line)"`
        if [[ $_age -gt $MAX_RETENTION ]]
        then
            VBoxManage snapshot "$1" delete "$(extractName $line)"
        fi
    done <  "$SNAP_LIST"
}

if [[ "$WEEK_ENDS" -eq $(date "+%u") ]]
then
    IS_WEEKLY=true
    PREFIX=weekly
    MIN_RETENTION=604800 # a week in seconds
    MAX_RETENTION=`expr $MIN_RETENTION \* $KEEP_WEEKLY`
else
    IS_WEEKLY=false
    PREFIX=daily
    MIN_RETENTION=86400 # a month in seconds
    MAX_RETENTION=`expr $MIN_RETENTION \* $KEEP_DAILY`
fi

for vm in "$@"; do
    # check if vm exists
    if [[ $(VBoxManage list vms | grep $vm) ]]
    then
        # get the age of the last snapshot
        LAST_SNAP_DATE=`getLastSnapDate "$vm"`
        SECONDS_SINCE=`getAge "$LAST_SNAP_DATE"`
        # if enough time has elapsed take a new snap
        if [[ "$SECONDS_SINCE" -ge $MIN_RETENTION ]]
        then
            takeSnapshot "$vm"
        fi
        fi
        # clean up old snapshots
        deleteOldSnaps "$vm"
    fi
done