Host key verification failed

A somewhat common error with ssh which usually happens because of the following:

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

A sample of the full error would be:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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 abc-xyz.com has changed and you have requested strict checking.
Host key verification failed.


If these two possible changes have not 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>"

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