I don't see anything wrong with what you are doing. That's the way I would do it:
Code:
su -l -c "/home/user/services/start-all.sh" user
which is the same, except that -l emulates a direct login. In Slackware 13.37,
I would also check /etc/group to make sure that user doesn't get extra permissions.
As an interactive user, I am in floppy, audio, video, cdrom, plugdev, power, and
netdev. A transmission-daemon would not need any of them, I believe. I am not even sure
I need them.