20.3.

20.3.1.

 ssh penguin.example.net 
The authenticity of host 'penguin.example.net' can't be established.
DSA key fingerprint is 94:68:3a:3a:bc:f3:9a:9b:01:5d:b3:07:38:e2:11:0c.
Are you sure you want to continue connecting (yes/no)?
Warning: Permanently added 'penguin.example.net' (RSA) to the list of known hosts.
 ssh username@penguin.example.net 
 ssh penguin.example.net ls /usr/share/doc