One process with multiple user ids.

[Giuliano Gagliardi <gogi-k@gogi.tv>]

Hello,

I have a server that has to switch to different user ids, but because it does 
other complex things, I would rather not have it run as root. I only need the 
server to be able to switch to certain pre-defined user ids.

I have seen that two possible solutions have already been suggested here on 
the LKML, but it was some years ago, and nothing like it has been 
implemented.

(1) Having supplementary user ids like there are supplementary group ids and 
system calls getuids() and setuids() that work like getgroups() and 
setgroups()

(2) Allowing processes to pass user and group ids via sockets.

Both (1) and (2) would solve my problem. Now my question is whether there are 
any fundamental flaws with (1) or (2), or whether the right way to solve my 
problem is another one.

Giuliano