How do I add an overlayfs to /etc/fstab?

Question

On Ubuntu v14.04, I have a drive mounted at /mnt/log-overlay that I would like to mount over the top of /var/log.

The following mount command successfully creates that overlay, and works fine:

mount -t overlayfs -o lowerdir=/var/log,upperdir=/mnt/log-overlay overlayfs /var/log

What do I need to add to /etc/fstab to make sure this overlay mounts at boot?

LABEL=cloudimg-rootfs   /    ext4   defaults,discard    0 0
/dev/xvde   /mnt/log-overlay    auto    defaults,nobootwait,comment=cloudconfig 0   2
[what-goes-here?]

Answer 1

From the figure-it-out-as-you-post-the-question department.

The following /etc/fstab entry successfully mounts /mnt/log-overlay on top of /var/log at boot:

overlayfs   /var/log    overlayfs   defaults,lowerdir=/var/log,upperdir=/mnt/log-overlay,comment=cloudconfig    0   2

Previous fstab entries:

LABEL=cloudimg-rootfs   /    ext4   defaults,discard    0 0
/dev/xvde   /mnt/log-overlay    auto    defaults,nobootwait,comment=cloudconfig 0   2