title: Jenkins 2.5 installation error (An error occurred during installation: Forbidden)
body: <p>I have a fresh CentOS box, installed Tomcat 8.0 and Jenkins 2.5. After entering the secret key for a brand new installation, the next step <em>Install</em> suggested plugins or :Select plugins to install:.  After clicking on <em>Install suggested plugins</em> I got an error saying</p>
  
  <blockquote>
    <p>An error occurred during installation: Forbidden</p>
  </blockquote>
  
  <p>I assume is related to folder permissions, the question is which one?</p>
  
  <p>UPDATE: The jenkins log says</p>
  
  <blockquote>
    <p>Found invalid crumb a711b93261896fb36a1d6ffbe163dca6.  Will check remaining parameters for a valid one...<br>
    May 21, 2016 4:19:34 AM WARNING hudson.security.csrf.CrumbFilter doFilter
    No valid crumb was included in request for /jenkins/administrativeMonitor/hudson.diagnosis.ReverseProxySetupMonitor/test. Returning 403.*</p>
  </blockquote>
  
  <p>Thanks in advance.</p>
  
  <p><a href="https://i.stack.imgur.com/n138A.png" rel="noreferrer"><img src="https://i.stack.imgur.com/n138A.png" alt="enter image description here"></a></p>