My distribution(Mandrake) came with a default set of users and groups. I have been trying to locate more information on what each group has access to and what their limitations are however to no avail.

I have noted the list of groups which I am unsure about.

1) nogroup
2) wheel
3) xgrp
4) rpc

Could someone please help me with what each group does and if I require them?

Just a note: I recall reading that wheel is a group for administrative tasks however what do those tasks involve and allow.

1) nogroup
Probably the equivalent group to the nobody user. It's just a convenience: a group with no privileges except those granted by the user and granted to all. Useful for cron scripts and similar.

2)
If you're using PAM, wheel is a group with special privileges. A classic example is to only allow users in the wheel group to su to root. As you have a wheel group, you probably are using PAM, though I wouldn't know how it so configured -- look for pam under /etc

3)
4)
Sounds like services from me. rpc is usually inter-program comminication, but with three-letter abbreviations, who knows? I do not know xgrp.

esben,

Thank you.