title: Nagios 4.0.7 upgrade thrown an error: "Unable to get process status"
body: <p>I have upgraded my <code>nagios core</code> to <code>4.0.7</code> and there are some errors when I log in my nagios web interface. </p>
  
  <p>First, there is an error message on the home page: <code>Unable to get process status</code>. </p>
  
  <p>Second, <code>nagios</code> seem not being able to execute any of it's plugin commands which reflects over the <code>localhost : check_ping</code> command returning the following status information: <code>(No output on stdout) stderr: execvp(/opt/nagios/nagios/libexec/check_ping, ...) failed. errno is 2: No such file or directory</code>. </p>
  
  <p>The problem is obvious here, it tries to execute the plugin commands from a wrong directory. After upgrading, all plugin commands are located in <code>/usr/local/nagios/libexec</code>. How do I tell <code>nagios</code> where to look for default commands?</p>
  
  <p>Thank you.</p>