(this is a post intended for Google - sorry for bothering you, faithful RSS readers)
I've been setting up encrypted backups for my Linux machine, found that cryptsetup gives a really cryptic and unhelpful error message:
$ cryptsetup luksFormat /dev/sda3 ~/.backupKey WARNING! ======== This will overwrite data on /dev/sda3 irrevocably. Are you sure? (Type uppercase yes): YES Failed to setup dm-crypt key mapping. Check kernel for support for the aes-cbc-essiv:sha256 cipher spec and verify that /dev/sda3 contains at least 133 sectors. Failed to write to key storage. Command failed. $
Google will suggest lots of things… But none of them solved my problem.
What was I doing wrong? I needed to run cryptsetup as root.
D'oh.