Introduction

Limiting the maximum amount of user processes is a way to prevent a user from hogging all the system resources, causing it to crash.

This can be done by editing either one of these two files:
(directories found in the Gentoo linux distro, use slocate <file> if you can't find it in other distro's.)
/etc/limits:
This is owned by the sys-apps/shadow package.
/etc/security/limits.conf:
This file is owned by the sys-libs/pam package

nearly all Distributions ship with the PAM package, but i will explain for both packages.

Please note that all numbers stated in here are purely as an example, and should not be used as a reference. My suggestion is to open a few applications, and see the number of processes used at that point, and taking that as a reference number.

/etc/limits

In this file, each line consists of a username (wildchart * is allowed), followed by a limitation code.

limitation codes

CODE :

Example

CODE :

/etc/security/limits.conf

Most people would want to edit this file, because it offers more flexibillity, and the abillity to set soft and hard limits.
soft: This generates a warning
hard: This just plain blocks the user from exceeding this limit, and will be logged.
Another advantage of this file over /etc/limits is that we can use groups to manage the users. We can do this by preceeding the group name with an '@' symbol.

File format

CODE :

Example

CODE :

Testing

If you wish to test if it worked, make sure that the new rules are loaded, and run a small forkbomb:
SAVE all important data before running this forkbomb.
CODE :

If your system still crashes, tighten up the number of processes a little bit, and try again.
(a simple reboot is the solution if your system hangs after running a forkbomb)

If you still have questions, feel free to pm me.