JConsole / JMX broken on Ubuntu

How annoying. I have just spent the last three hours trying to connect to Tomcat remotely using JConsole/JMX. It worked fine for one server, but not the other which was started with exactly the same settings. Eventually I found the problem: Ubuntu maps the hostname to 127.0.0.1 in /etc/hosts by default and this breaks the JMX protocol. It seems that JMX opens a separate socket stream for data (like FTP) and needs to provide the host's network address to do this.

Actually, my problem was already documented in the FAQ:
http://java.sun.com/j2se/1.5.0/docs/guide/management/faq.html

On a side note, I also had problems with Netbeans 6.0 being dog slow on Ubuntu. It seems to have had something to do with the GTK look and feel, because I fixed it by adding --laf javax.swing.plaf.metal.MetalLookAndFeel to the startup options in ${nbhome}/etc/netbeans.conf. It runs great now.

About Roger Keays

Roger is an active member of the JSF 2 Expert Group and is happy to be a contributor to the Java Community. He has been writing software since the age of 8 and his other interests include languages, science, travel and surfing. You can follow Roger on Twitter and Google+.