title: How to establish ssh key pair when "Host key verification failed"
body: <p>I have set up ssh key pairs between my desktop and two servers, and from the servers to my desktop, but after reinstalling the OS on my desktop, I can't re-establish the key-pair going into my desktop by this:</p>
  <pre class="lang-sh prettyprint-override"><code>mkdir ~/.ssh
  chmod 700 ~/.ssh
  ssh-keygen -t 
  ssh-copy-id username@server
  </code></pre>
  <p>I get the following error:</p>
  <p>(names in <em>italics</em> changed to protect the innocent My desktop is Ubuntu, and I can't find the answer <a href="https://help.ubuntu.com/community/SSH/OpenSSH/Keys" rel="noreferrer"> here</a>)</p>
  <blockquote>
  <p>@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  @    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
  <em>ab:cd:ef:gh</em>
  Please contact your system administrator.
  Add correct host key in /home/<em>user</em>/.ssh/known_hosts to get
  rid of this message.
  Offending key in /home/<em>user</em>/.ssh/known_hosts:1
  RSA host key for <em>user.server</em> has changed and you have requested strict
  checking.
  Host key verification failed.</p>
  </blockquote>