when I use pssh, trying to access a remote machine which is not inside the UNIX 
known hosts file, pssh freeze after giving the password.
After having added the host using a direct ssh command, pssh works.
So is there an option to give to the pssh command in order to avoid this problem ?
Thanks for your help,
Regards
Try pssh -O StrictHostKeyChecking=no. This works for me.
By default ssh uses the value of "ask", which causes it to ask the user whether to continue connecting to unknown host. By setting the value to "no", you avoid the question, but are no longer protected against certain attacks. E.g. if you are connecting to hostA, and someone puts hostB there with the same IP address, then by default ssh will notice that hostB has changed, and will prompt you about it. With StrictHostKeyChecking=no, it will silently assume everything is OK.
pssh and known_hosts file