I am running Ubuntu server edition and I wanted to take a thread dump of Tomcat. So, I first tried to find out which PID tomcat uses: $ jps -l 5809 sun.tools.jps.Jps But it's not there? So, I used top instead and found out the PID 5730. Then I called jstack to get the thread dump: $ sudo jstack -l 5730 5730: Unable to open socket file: target process not responding or HotSpot VM not loaded The -F