Hi

I am using the dialing commands pon/poff to start pppd.
pppd has the stick bit set so that it runs as root.

I have 2 non-superusers that can successfully start pppd using the pon command, and I can see that pppd indeed is running as root.

What I don't understand is that the user that started pon is able to successfully call poff and kill pppd, however the other user cannot kill pppd.

I would think that since pppd is running as root, neither should be able to kill it. How does pppd have any memory of who called it if it is now running as root?

Thanks

I'm not 100% sure how it works, but I do know that Linux processes actually have two user IDs, the real userID (belonging to the person who started the process) and the effective user ID (i.e. 0 if the setuid bit is set and the executable is owned by root). My guess is that the kill system call checks both the real and effective user ID (and reading the kill(2) man page confirms this impression). Processes also have real and effective group IDs as well.