/usr/lib/util-vserver/defaults/fstab is in util-vserver 0.30.216-pre2864-2ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3  | none	/proc		proc	defaults		0 0
none	/tmp		tmpfs	size=16m,mode=1777	0 0
none	/dev/pts	devpts	gid=5,mode=620		0 0
 |