Comment 20 for bug 1453912

I can confirm the exact same behavior: if /etc/crypttab has entries for non-root devices, then the only way to unlock with a password is to force plymouth to run with the "splash" boot option.

I've been trying to test luks-encrypted data volumes (non-root) on ubuntu-server and have hit this problem for 15.04, 15.10, and 16.04 daily...basically ever since the switch to systemd. Worse, adding "splash" doesn't actually resolve the problem on ubuntu-server...perhaps due to a broken/incomplete plymouth install?

I ended up testing ubuntu-desktop 15.10 on a whim with "splash" and that was the first time I was able to enter the password to unlock the devices.

It seems like this is a problem with the systemd-ask-password-console service. I've tried to test the theory by creating an extremely simple "oneshot" service script that requires systemd-ask-password-console and runs "/bin/systemd-ask-password --no-tty 'Test'". I've tried all manner of systemd service options and I can't for the life of me get systemd-ask-password-console to prompt for a password.