Is it possible to disable PASSWORD SSH access to user but to allow Key authentication on a per user basis ? I mean, I have a userA whom I don't want to give Password based access BUT I wan't him to only use key authentication to access the server(s). Thanks
Just lock the passwords of the users you don't want to log in with passwords:
usermod -L <user>
Then, place a valid public key in their
.ssh/authorized_keys file and they will be only able to log in with the corresponding private key, but not with a password.
Note: This will break sudo unless the user has NOPASSWD: in their visudo entry