Use the AuthorizedKeysFile directive in sshd_config to point to a file only you have access to, outside the user's home directory. However, this won't allow you to use a single file, unless you want all users to have access to everyone's accounts. Off the top of my head, I can't think of a way to do it with a single file.
-----Original Message----- How do I configure openssh so that it'll permit a public key for a user, without giving the user the oppertunity to change/add public keys to the authorized list? Also, is there a way to have a single file with the authorized keys for *all* users? Like /etc/shadow, but for public keys rather than passwrods.
