Neat way to getting consistent backups of stuff by utilizing LVM snapshots. In my setup /backuptarget is an USB hard drive, but it could be sshfs, smb or nfs share just as well.

backup.sh

#!/bin/sh

. /etc/environment

lvcreate -l90%FREE -s -n rootsnap /dev/host/root

#XFS specific: Mounting ignoring uuid because the original volume has same uuid
mount -o ro,nouuid /dev/host/rootsnap /mnt/rootsnap

mount /backuptarget

#Purge history
rdiff-backup --remove-older-than 1Y /backuptarget/stuff

#Actual backup
rdiff-backup --exclude /mnt/rootsnap/stuff/NotInNeedOfBackingUp /mnt/rootsnap/stuff /backuptarget/stuff

umount /backuptarget
umount /mnt/rootsnap
lvremove -f /dev/host/rootsnap