How to create custom Fork Bomb Protection settings

Question

How do you create custom Fork Bomb Protection settings?

Answer

The following can be implemented to set a custom set of ulimit settings by Fork Bomb Protection. 

Note: When done, Fork Bomb Protection will show as disabled in WHM.

1. Make sure Fork Bomb Protection is disabled in WHM at Home / Security Center / Shell Fork Bomb Protection.

   Note: Shell Fork Bomb protection is unavailable on CloudLinux servers since it uses LVEs.

2. Create the following file /etc/profile.d/mylimits.sh with the following contents:

   CONFIG_TEXT: # Custom Shell Fork Bomb Protect
   ulimit -n 4096 -u 14335 -m unlimited -d unlimited -s 8192 -c 1000000 -v unlimited 2>/dev/null
   LIMITUSER=$USER
   if [ -e "/usr/bin/whoami" ]; then
   LIMITUSER=$(/usr/bin/whoami)
   fi
   # Limit the user only if we are not root and are a regular user (UID greater
   # than or equal to UID_MIN).
   if [ "$LIMITUSER" != "root" ] &&
   ! id -Gn | grep -qsP '(^| )wheel( |$)' &&
   [ "$(id -u)" -ge "$( (grep -s '^UID_MIN' /etc/login.defs || echo 'x 500') | awk '{print $2}')" ]
   then
   ulimit -n 1200 -u 250 -m 200000 -d 200000 -s 8192 -c 200000 -v unlimited 2>/dev/null
   else
   ulimit -n 4096 -u 14335 -m unlimited -d unlimited -s 8192 -c 1000000 -v unlimited 2>/dev/null
   fi

   The main change so far is increasing the number of open files to 1200 and the number of user processes to 250.

3. Set permissions for /etc/profile.d/mylimits.sh with the following command:

   # chmod 755 /etc/profile.d/mylimits.sh

4. Next we need this to be contained in /etc/bashrc and /etc/profile by doing the following to concatenate to those files:

   # cat /etc/profile.d/mylimits.sh >> /etc/bashrc

   # cat /etc/profile.d/mylimits.sh >> /etc/profile

At this point, the custom Fork Bomb Protection settings are enabled. Please keep in mind the user will need to log out and log in again so that the /etc/profile and /etc/bashrc files get loaded for the user.

Additional Resources

How to disable/enable fork bomb protection