Hi,
Why would you need to run it as different user than the default one?
If this is just a step to security through obscurity - simple trick would
be to change the username in the passwd/shadow file - keeping the user id.
Otherwise you'll need to change some directory ownership and permissions -
for example var and run related directories, where the process needs to
'operate' - create/modify/delete files.
Good luck
P.S. strace is your friend