Backup KVM virtual machine hard disk images

backup-kvm-vms.sh

#!/bin/bash

set -e

VMPATHS=()
VMNAMES=()
VMCONFS=()
SSPATHS=()
TGZNAME=/srv/backups/vmbackup-`date '+%y%m%d-%H%M%S'`.tar.gz
TGZLINK=/srv/backups/vmbackup-current.tar.gz

cleanup() {
	for vm in ${VMNAMES[*]}
	do
		echo blockcommit snapshot for VM \"$vm\"
		virsh blockcommit $vm vda --active --pivot --shallow --verbose
	done

	echo deleting snapshots and config files
	rm -f ${SSPATHS[*]} ${VMCONFS[*]}
}
trap cleanup EXIT

for vm in $@
do
	VMNAME=$vm
	VMPATH=/var/lib/libvirt/images/$VMNAME.qcow2
	VMCONF=/tmp/$VMNAME.xml
	BKNAME=$VMNAME-`date '+%y%m%d-%H%M%S'`
	SSPATH=/srv/snapshots/$BKNAME.qcow2
	
	VMNAMES+=($VMNAME)
	VMPATHS+=($VMPATH)

	echo saving snapshot xml $VMCONF
	virsh dumpxml $VMNAME > $VMCONF
	VMCONFS+=($VMCONF)

	echo creating snapshot for VM \"$VMNAME\" to \"$VMPATH\"
	virsh snapshot-create-as --domain $vm $BKNAME --diskspec vda,file=$SSPATH --disk-only --atomic --no-metadata
	SSPATHS+=($SSPATH)
done

tar cf - ${VMPATHS[*]} ${VMCONFS[*]} | pigz -p 3 > $TGZNAME

rm -f $TGZLINK

# only keep most recent 3 backups
ls -tp | grep -v '/$' | tail -n +4 | xargs -d '\n' rm --

# relink the current backup
ln -s $TGZNAME $TGZLINK

Check https://github.com/abbbi/virtnbdbackup for an alternative approach.