Nice description how easy it is to install hudson under Ubuntu:
The biggest advantage is the automatic update with apt.
Ok after playing around it’s easier to download the WAR-File and deploy it in my Tomcat6. After that you will get a nice AccessControlException, which blocks the access to a Class because of the Security Manager. This can be disabled with editing the “/etc/default/tomcat6″.
Solution was found here: http://testinfected.blogspot.com/2009/01/hudson-gets-accesscontrolexception-when.html
After you did this you should add the -DHUDSON_HOME=… in /etc/default/tomcat6 and do a chown, because the tomcat is running under the user tomcat6 and will not have enough rights, to create files there.
Also found some of the hints here: http://adelio.org/hudson-installieren-tomcat-ubuntu-9-10/