Restrict ssh logins

["Eric d'Alibut" <eric.halibut@gmail.com>]

I want to tighten up network logins to a Debian stable machine.

I want to turn off ordinary unix password logins. and I want restrict
ssh logins to only users with an ssh pub key in their authorized_key
files (to be placed there by me, your friendly sysadmin).

Any pointers as to how to do this, or as to where to find pertinent
docs, would be greatly appreciated.

--
No no no, my fish's name is Eric, Eric the fish. He's an halibut. I am
not a looney! Why should I be tarred with the epithet looney merely
because I have a pet halibut?