I have downloaded Lucene 3.0.0 and when I used the command java -jar lucene-core-3.0.0.jar in the directory where Lucene is present I got this message
java -jar lucene-core-3.0.0.jar
Failed to load Main-Class ...
EDIT I've written up a quick howto on getting multicore going: http://charlesleifer.com/blog/solr-ubuntu-revisited/ Following instructions from the two sites below, I've installed Tomcat 6 and Solr 1.4.