su and shutdown questions

[Aaron Prohaska <verdesoft verdesoft net>]

I have been trying to make it possible for a regular user to run the
ppp-on script, but can't seem to make it work. Every time I try to run
ppp-on from my user account I get a "permission denied" message. What I
originally tried to  was chmod +x ppp-on, but it seems like it didn't
work. So what I am currently do is su to root and start ppp-on, then
exit and log into my user account. That seems to solve my connecting
problems, but I would like to be able to do this as user. This leads me
to my second problem, once I have logged in as a user and I want to
shutdown I have to su to root to do it. This is fine except once I am
root and I type 'shutdown -h now' bash tells me 'command not found'. So
with some playing I descovered that I have to type '/sbin/shutdown -h
now'. I guess my question regarding this is why can I just type
'shutdown -h now' from any location when I log in as root, but if I have
to su to root I have to type '/sbin/shutdown -h now'?

This seems very strange.

Thanks,

Aaron