Basic LVM snapshot to file for Xen domU.

xen lvm snap

#!/bin/bash

[ $# -ne 2 ] && { echo "Usage: ./snap <lvm group> <domU>"; exit 1; }

##
# Export an LVM device to file
#
# @param string $1 LVM_GROUP The logical volume manager group (e.g. vg0)
# @param string $2 DOMU      The guest domain to snap (e.g. w01)
#
function snaplvm() {
    local LVM_GROUP=$1
    local DOMU=$2
    
    DEVICE=/dev/${LVM_GROUP}/${DOMU}-disk
    SNAP_DEVICE=/dev/${LVM_GROUP}/${DOMU}-snap
    SNAP_FILE=${HOME}/${DOMU}.snap
    
    # Test block device exists
    [ -b ${DEVICE} ] || {
        echo "${DEVICE} does not exist!"
        return 1
    }
    
    # Delete old snap
    [ -f ${SNAP_FILE} ] && {
        read -p "Delete previous snapshot? [y/n]" REPLY
        [[ $REPLY == "y" ]] && rm ${SNAP_FILE} || {
            echo "Aborting..."
            return 1
        }
    }
    
    echo "Creating snapshot volume..."
    lvcreate -L 1G -s -n ${DOMU}-snap ${DEVICE} && {
    
        echo "Taking snapshot of ${DEVICE}..."
        dd if=${SNAP_DEVICE} of=${SNAP_FILE} && {
    
            echo "Deleting snapshot volume..."
            lvremove ${SNAP_DEVICE}
    
            echo "Completed ${SNAP_FILE}"
            return 0
        }
    }
}

snaplvm $@ && echo "Success!" || echo "Failed!"