systemd-initrd: add test to ensure that the permissions on the systemd generators are correct

          newAvail = machine.succeed("df --output=avail / | sed 1d")

          assert int(oldAvail) < int(newAvail), "File system did not grow"

      with subtest("no warnings from systemd about write permissions"):

          machine.fail("journalctl -b 0 | grep 'is marked world-writable, which is a security risk as it is executed with privileges'")

    '';

  }

)