title: Jenkins slave node is offline : Authentication failed
body: <p>My jenkins slave node is offline. The log is as follows:</p>
  
  <pre><code>[06/11/15 09:02:52] [SSH] Opening SSH connection to &lt;ip&gt;.
  ERROR: Server rejected the 1 private key(s) for jenkins (credentialId:d7a17c00-1300-4cf3-8cf5-810b3297ebc6/method:publickey)
  [06/11/15 09:02:52] [SSH] Authentication failed.
  hudson.AbortException: Authentication failed.
      at hudson.plugins.sshslaves.SSHLauncher.openConnection(SSHLauncher.java:1178)
      at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:701)
      at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:696)
      at java.util.concurrent.FutureTask.run(FutureTask.java:262)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
      at java.lang.Thread.run(Thread.java:745)
  [06/11/15 09:02:52] Launch failed - cleaning up connection
  [06/11/15 09:02:52] [SSH] Connection closed.   
  </code></pre>
  
  <p>I have verified below:</p>
  
  <ol>
  <li>Authorized_keys file at /var/lib/jenkins-slave/.ssh has correct public key of master.</li>
  <li>Authorized_keys file at /var/lib/jenkins/.ssh has correct public key of master.</li>
  <li>Master has its private and public key files at /var/lib/jenkins/.ssh folder and also at ~/.ssh folder.</li>
  </ol>
  
  <p>I also tried "ssh -i .ssh/id_rsa -l jenkins ” from master machine but it is asking for password. Looks like it is not identifying slave machine.</p>
  
  <p>There is known_hosts file in .ssh folder of both master and slave machine.
  What data goes in there?</p>
  
  <p>How to resolve the issue?</p>