I have a suggestion for the FAQ.
Had to do a password recovery. Logged in via SSH using another username, ran "sudo passwd admin". Couldn't log in to the web interface. Did some more checking and found that there's an omv-firstaid utility, likewise changed the password in there. It still didn't let me log in. Started digging for more information, including trying the default openmediavault password, finally using both passwd and omv-firstaid, still didn't seem to work.
After spending time playing with recovering my password for this forum on a lark I tried the web console one last time and the password finally worked. It appears that there's a delay between setting the password and being able to use it. This delay is not enumerated anywhere that I saw, either as a message from the omv-firstaid utility or in the forums.
Some further documentation on the nature of administration would be nice. I honestly don't know which process actually triggered the password reset, and I don't know if the old GNU passwd utility did anything at all or caused worse problems. Please consider adding some of this to the FAQ lest other long-time Linux users find themselves in the same situation where expected commands either don't work, cause harm, or take time.