SSH Troubleshooting

• If you have problems with SSH, here are some troubleshooting pointers:
  Run ssh -v (verbose option) to see additional information, which is often helpful.
• If the ssh-daemon is running on a port different from the conventional 22, make sure you are specifying port -p 221 (for instance).
• Check that your home directory or SSH subdirectory does not allow world or group write access.
• If you are attempting to use RSA authentication, check that you have not introduced carriage returns when copying identity.pub contents into the authorized_keys file.
• When you are asked:
  Host key not found from the list of known hosts.
  Are you sure you want to continue connecting (yes/no)?
  
  Respond yes, but be aware the response should be yes and not y.
  
  If you see a message that begins:
  @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  WARNING: 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)!
  . . .
  Are you sure you want to continue connecting (yes/no)?
  
  it is likely that the host key in use by the remote system has been changed. Here is what to do:
  
  Edit your local ~/.ssh/known_hosts file to remove lines containing the name of the host you were attempting to reach.
  Retry the SSH command and when asked "Are you sure you want to continue connecting?" answer "yes."
  
• Is SSH possible? The host you are trying to access must have SSH installed and must be running the SSH daemon.
• If your SSH usage involves non-interactive connections such as with pvm or batch submissions, a passphrase cannot be used.

Further reading:A good article is on http://www.llnl.gov/computing/hpc/access/ssh_outside.html