Users, groups and directory access

[A.J. Bonnema]

Hi,

I have a simple access I would like to solve. Reading the RedHat 
documentation on users and groups didn't help sufficiently. Maybe one of 
you guys, sysadmins, could help?

I'm running a up to date Fedora core 1 (no test packages).

The problem is:

1. I have a user let's say john with two gid's: one for john and one for 
  proj. The group john is his primary group.

2. I also have a directory owned by user paul and he want everyone in 
group proj to be able to read and write and create directories and files 
in his directory /project. So (using the reference guide from red hat) 
he creates a directory /project and has the admin do the following 
sequence of commands:

/usr/sbin/groupadd proj
chown -R paul.proj /project
/usr/bin/gpasswd -a john proj
chmod 2775 /project

{from chapter 6.4.1 Group Directories of the redhat ref. guide]

Stil, as long as proj is not the primary group of john, he is not able 
to create directories or files. As soon as john makes his primary group 
proj, it works.

Now I have 2 questions:
1.
Is there any way, to have all groups a user is member of, effective 
simultaneously?
2.
How can john change his primary group on the commandline?

I appologize for not knowing (or being able to find) these simple 
answers on my own.....

Guus.
-- 
A.J. Bonnema, Leiden The Netherlands,
user #328198 (Linux Counter http://counter.li.org)