After some moving of partitions, my Ubuntu Mate still boots, but strangely it asks for a passphrase for the cryptswap1 volume. I don’t enter anything and hit enter and it works. As I understand it, the swap partition only needs a random passphrase on every boot process. But how can I make the prompt disappear and Ubuntu figure out a passphrase without user interaction?
Had the same problem with Ubuntu 16.04.3 LTS after removing OEM Windows10 partition. Apparently this has been fixed, but not backported to Xenial. Reinstalling the cryptfs package did the trick for me:
$ sudo apt install ecryptfs-utils --reinstall $ sudo update-grub
I was having the same problem and found this bugreport on launchpad. Its status said "Fix Released". So I just upgraded my Ubuntu (from 16.04 to 16.10) and I was never asked for a cryptswap password anymore.