Comment 11 for bug 1489563

I tested the Ubuntu (running on my HP ProBook 455 G1) and Kubuntu (running in VirtualBox) 16.04 (both up2date) with same Systemback version, Casper 1.376 and kernel 4.4.0-21-generic.
The unionfs-fuse is a (slow) backup solution, used when no overlay, overlayfs, aufs or unionfs support in the kernel. But the Ubuntu kernel contains the aufs (default in the oldest Ubuntu releases) and the overlay (default in the 16.04 and this is the official solution in the vanilla kernel), see the following command output:

cat /boot/config-$(uname -r) | grep -e AUFS -e OVERLAY

Both are in the kernel in module format. If you wish to choose between them, just edit the kernel parameters (TAB with Syslinux and 'E' with UEFI):

UNIONFS=overlay
UNIONFS=aufs
UNIONFS=unionfs-fuse

See these screenshots:
http://logout.hu/dl/upc/2016-05/180556_set.png
http://logout.hu/dl/upc/2016-05/180556_aufs.png
http://logout.hu/dl/upc/2016-05/180556_overlay.png
http://logout.hu/dl/upc/2016-05/180556_unionfs-fuse.png

As you see I do not found any problem.
Currently the Systemback 1.8.999 contains a little debug fix, but otherwise equal with the stable version (1.8.300). So the plus tests with the stable version is not necessary.