def run_solr
    defs = {
      'jetty.home'    => @path,
      'solr.data.dir' => @path/'solr'/'data'
    }.map { |k, v| "-D#{k}=#{v}" }.join(' ')
    
    cmd = "java -jar #{@path}/start.jar #{@path/'etc'/'jetty.xml'} -classpath #{@path/'lib'} #{defs}"
    
    # IO.popen is more portable than fork/exec (i.e. to JRuby)
    pid = IO.popen(cmd, 'r').pid
    puts "PID: #{pid}"
    
    pid
  end