Forcing users to use public SSH keys to authenticate

Here are the steps I use when I create a new user account on a secure SSH server (where only public keys are allowed).

# useradd -m username
# passwd username
(paste in a super-long randomized password)
# cd /home/username
# su username
$ mkdir .ssh
$ chmod 700 .ssh
$ cd .ssh
$ cat > username@linux.pub
(paste in the public key file from SecureCRT)
$ ssh-keygen -i -f username@linux.pub >> authorized_keys
$ chmod 600 *

At this point, the user should be able to login via SecureCRT using their private/public key pair. There's no need for them to know the password that you assigned to them on the server (so use something random and at least 30+ characters).