Thanks to Cloudera's CDH3 image, I have a virtual machine with Hadoop on CentOS 5 working. I'm more of an Ubuntu guy, so CentOS is a new for me. But nothing Google couldn't solve. I also ran into a Hadoop exception about the java heap space. I couldn't find a solution online so I just bumped up the memory on the virtual machine and it solved the problem. In any case, I managed to run the pi calculation example on my local Hadoop cluster.