1. LE PROBLEME

Tous les admins connaissent cet infâme situation lors d'une connexion en SSH (vraiment casse-couille) 
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
c0:69:25:fb:24:a6:6f:3f:01:77:69:27:a3:5f:83:e1
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending key in /root/.ssh/known_hosts:26
Password authentication is disabled to avoid man-in-the-middle attacks.
Keyboard-interactive authentication is disabled to avoid man-in-the-middle attacks
Permission denied (publickey,password).

2. LA SOLUTION

Ajouter ces deux lignes dans le fichier /etc/ssh/ssh_config 
Host *
.....
.....
   StrictHostKeyChecking no
   UserKnownHostsFile /dev/null
:)

SOURCE: http://linuxcommando.blogspot.com/2008/10/how-to-disable-ssh-host-key-checking.html