How to limit it ?

[Grzegorz Pawel Szostak <grzecho@ikar.mps.com.pl>]

Hi!
I'd like to limit some resources on my server for one user group. since
now i thinked that lshell will be good enough but ulimit -a says:
ikar:~$ ulimit -a
core file size (blocks)     0
data seg size (kbytes)      15360
file size (blocks)          unlimited
max locked memory (kbytes)  unlimited
max memory size (kbytes)    unlimited
open files                  24
pipe size (512 bytes)       8
stack size (kbytes)         8192
cpu time (seconds)          unlimited
max user processes          15
virtual memory (kbytes)     unlimited

how to limit all of this ?
I've tried /etc/security/limits.conf but it seems to not work properly ...

Thanx !

G.