1. As root: vi /etc/security/limits.conf #add the following line, where steve is the user: sburke hard nproc 5 #save and close the text editor. #The user will not be able to run more than 5 processes at the same time.

2. ssh sburke@localhost ps -eaf | grep sburke | ls /var/tmp | less -bash: fork: Resource temporarily unavailable

References:

http://www.debian.org/doc/manuals/securing-debian-howto/ch4.en.html#s-user-limits

http://www.cyberciti.biz/tips/linux-limiting-user-process.html