When I'm trying to install maven2 I just "add maven", give it a name, leave
install automatically checked, choose appropriate version to be installed (e.g.
2.2.1), and save configuration. Then in a build job configuration I chose
previously added maven, save the job, and start a build. Problem is that build
fails with console output printing following:

...
ERROR: No classworlds*.jar found in /var/lib/hudson/tools/Maven_2.2.1 – Is this
a valid maven2 directory?
Finished: FAILURE

With groovy script I've checked, maven archive has been downloaded and unpacked
but not where hudson build is looking for it, it's in
/var/lib/hudson/tools/Maven_2.2.1/apache-maven-2.2.1.