Despite what I had said previously, I’m now not recommending installing solr & tomcat from ubuntu packages.
The version of solr that is provided by Ubuntu 9.10 is solr 1.2, which is over 2 years old. Installing directly from the solr .jar is likely better.
Tomcat was kind of pain in the ass anyway. 
NOTE: THE VERSION OF SOLR PROVIDED BY UBUNTU IS ONLY 1.2. THIS VERSION IS OVER 2 YEARS OLD.
You can fairly easily install tomcat & Solr for Ubuntu via apt-get, but there are some quick caveats before you begin. The packages are in the base repositories, but something is messed up with the dependencies, so you can’t just say “sudo apt-get install solr-tomcat5.5″ unless tomcat is already installed. So, the right sequence is:
$ sudo apt-get install tomcat5.5 $ sudo apt-get install solr-tomcat5.5
I’m a bit nervous that solr doesn’t seem to work with (or rely on) newer versions of tomcat, but I’m to to stressed at the moment. Once you’re done with the above, you can check your Solr install at http://localhost:8180/solr/admin
Solr config files live in /etc/solr/config/…
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