ssh-copy-id nos permite generar nuestra propia clave RSA y copiarla a los servidores que queramos, y de esta forma ya no será necesario escribir el password de cada servidor.
Primero generamos la contraseña y no le ponemos password.

# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
be:11:15:e3:6a:dc:a6:a6:7e:e9:6c:7b:9f:30:28:40 root@poe
The key's randomart image is:
+--[ RSA 2048]----+
| o |
| . o |
| E o |
| . . + |
| . S o |
| . o = |
| . *.o |
| =+o.o . |
| .o+=o .o |
+-----------------+

Ahora copiamos la clave al servidor

# ssh-copy-id -i .ssh/id_rsa.pub root@192.168.1.254

The authenticity of host '192.168.1.254 (192.168.1.254)' can't be established.
RSA key fingerprint is db:d0:45:cc:78:cf:10:4a:c6:80:c5:ff:a6:10:3a:43.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.1.254' (RSA) to the list of known hosts.
root@192.168.1.254's password:
Now try logging into the machine, with "ssh 'root@192.168.1.254'", and check in:
~/.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.

Y ahora intentamos conectar al servidor :

# ssh root@192.168.1.254
Last login: Sun Jun 26 19:33:41 2011

Si elegimos poner contraseña a nuestra clave RSA, cada vez que hagamos uso de la clave nos pedirá el password, de forma que sólo necesitamos recordar un password

# ssh root@192.168.1.254

 Enter passphrase for key '/root/.ssh/id_rsa':

Si queremos comprobar en el servidor qué usuarios tienen acceso, tenemos que echar un vistazo al archivo  .ssh/authorized_keys :

# cat .ssh/authorized_keys

ssh-rsa ----clave ---- usuario@equipo
ssh-rsa ----clave----- usuario@equipo