Common Unix Errors and Solutions

Cannot log in with SSH: Host Identification Error

 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
 @    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
 eb:2b:5f:c3:5e:31:ff:c7:41:2f:c7:bd:ea:18:50:3f.
 Please contact your system administrator.
 Add correct host key in /Users/username/.ssh/known_hosts to get rid of this message.
 Offending key in /Users/username/.ssh/known_hosts:12
 RSA host key for fmri00-miles.hosted.ats.ucla.edu has changed and you have requested strict checking.
 Host key verification failed.

This error is likely to occur after:

• a system has been updated
• if its IP has changed

If neither of these have occurred, there *may* be need for concern. However, if these sorts of changes are going on it is perfectly safe to resolve this error with one of the two following fixes.

The first is a bit easier/straight forward, but will require that you reaccept (type "yes" at first ssh login) all future server logins:

$ rm ~/.ssh/known_hosts

The second is more graceful. It will retain all your past acceptances and only require that you reaccept the current, problematic one:

1. open ~/.ssh/known_hosts in a text editor
2. Remove the line that starts with: "<server host name causing the error>,<server IP causing the error>"

For example, if fmri00-miles.hosted.ats.ucla.edu were producing the error the line that you'd delete would start with something like this:

fmri00-miles.hosted.ats.ucla.edu,164.67.183.62 ssh-rsa

• Hint Use the text editor's search feature, sometimes known_hosts files can have quite a few lines.