[olug] Sharing root priv, tracking what other root does

[netsaint at cox.net]

I’m looking for a way to track what another root user does on a sensitive Linux server that I have had exclusive control of.  Recently, I was strong-armed into giving root access to another.
Prior to sharing control I made it very clear, “you break it and I kill you”!  When this new root user breaks it, and he/she/it will, I should be able to recover nicely using AMANDA.
Perhaps my emphatic statement was enough, to date, he/she/it has not attempted to login as root.  ;-)
Any of you admins have experience in anything?  If so, how did you remedy it?