(Just for the sake of remembering my own damn self — and maybe helping someone else.)
Earlier, I attempted to hibernate my desktop. Never done it in the 15 months I’ve had Ubuntu 8.04 LTS on here, so I figured “Hell, why not?” I hit the dropdown, and the system commenced its hibernating shutdown action. But it neither shut off nor came back to life. I ssh’d into it to discover via the system logfile that the hibernate was halfway through its operations when the power daemon discovered “Oh Hell! There’s no resume device on this machine!” at which point it ceased and attempted to raise the machine from the dead.
After manually power-cycling the system, I did some digging. Turns out the UUID of the swap/resume partition had been changed somewhere along the way, so both /etc/fstab and /etc/initramfs-tools/conf.d/resume were stuck with the old UUID from way back when the system was installed. That UUID no longer exists.
I’m not sure what caused it to change; such an idea is disturbing, considering this is supposed to be the super-stable, LTS build of Ubuntu. The UUID of the swap partition is usually set with the mkswap -U command, and can be set on an ext2/ext3 partition with the tune2fs command. But anything can go wrong.
So. How to make fix? A quick check with sudo blkid will list the block devices on the system:
oldman@Deskie:~$ sudo blkid /dev/sda1: UUID="c97b2e80-a5b2-4371-a60e-126a8d1402a5" TYPE="ext3" /dev/sda5: TYPE="swap" UUID="f3a3cd16-f0c8-40a1-8a7d-578c57296c6b" /dev/sda6: UUID="775a56e3-0244-453f-8d8a-fd1eb42a82f6" / SEC_TYPE="ext2" TYPE="ext3"
The swap partition has the UUID f3a3cd16-f0c8-40a1-8a7d-578c57296c6b and is the device /dev/sda5. Copy and paste the UUID into the fstab and resume config files to replace the UUID that was there. Execute sudo swapon -a to mount your swap partition, and you should be golden. Verify with free -m to check for a nonzero swap size.
oldman@Deskie:~$ free -m total used free shared buffers cached Mem: 3962 1784 2178 0 154 660 -/+ buffers/cache: 969 2993 Swap: 11601 0 11601
The value 11601 tells me I’m gettin’ my swap on. Aw yeah.