    # File lib/mongrel/configurator.rb, line 55
        def change_privilege(user, group)
          begin
            uid, gid = Process.euid, Process.egid
            target_uid = Etc.getpwnam(user).uid if user
            target_gid = Etc.getgrnam(group).gid if group

            if uid != target_uid or gid != target_gid
              log "Initiating groups for #{user.inspect}:#{group.inspect}."
              Process.initgroups(user, target_gid)

              log "Changing group to #{group.inspect}."
              Process::GID.change_privilege(target_gid)

              log "Changing user to #{user.inspect}."
              Process::UID.change_privilege(target_uid)
            end
          rescue Errno::EPERM => e
            log "Couldn't change user and group to #{user.inspect}:#{group.inspect}: #{e.to_s}."
            log "Mongrel failed to start."
            exit 1
          end
        end