I have a linux mint 18 installation with a luks encrypted / and swap partitions.
/ which is
/dev/sda6 unlocks and mounts fine at boot up. The system then goes into emergency mode. journalctl says timeout trying to reach the swap partition.
I tried running
cryptsetup open --type luks /dev/sda5 sda5_cryptand that returns
Device /dev/sda5 is not a valid LUKS device.