How to service builders?

[Michael Schwendt]

As an example, currently the builder status says

  xenbuilder2.fedora.redhat.com  (unavailable)

but

  xenbuilder2 ~]$ /sbin/service plague-builder status
  plague-builder (pid  1939) is running...

so assuming I wanted to restart it as a simple first step, where do
I find the documentation? Basically, I would be interested in whether
it requires root privileges and what role the account system groups
play (if any).