Run radrelay as a different user

[Eric Merkel]

Sorry if this is too basic of a question but I've been fighting with
this for a while and google hasn't turned up anything for me.

I am running freeradius on Centos and it runs the freeradius daemon as
the radiusd user&group. However when I start radrelay it starts as
root which then changes the detail file to be owned by root thus
causing radiusd not to be able to write any further accounting packets
to the file.

I've tried starting radrelay as the user radiusd as follows but its not working.

# su -c 'radrelay -xx -s SecretPass -r 192.168.1.4:1645
/var/log/radius/radacct/detail' radiusd

I do not get any debug information back it just goes back to the
prompt and radrelay doesn't start.

Is there another way of making radrelay run as the user radiusd?

I guess I could change radiusd to run as root or make the detail file
permissions world writeable but I would like to avoid doing either of
those if at all possible.

-Eric