x-systemd.automount & CIFS shares in fstab
Solution 1:
systemd was introduced in ubuntu 15.04.
After adding x-systemd.automount to an fstab line, you need to run:
sudo systemctl daemon-reload
and then one, or both, of the following:
sudo systemctl restart remote-fs.target
sudo systemctl restart local-fs.target
only then will the automount become active.
Solution 2:
Ubuntu doesn't use systemd, so x-systemd.automount won't work. I guess it is just interpreted as an invalid mount option.
If you want to have your CIFS share mounted on-demand have a look at this: http://wiki.ubuntuusers.de/Autofs