Overview

When you are setting up a new Linux computer (or an existing one that you have made changes on), you may run into the following error when attempting to elevate to “root” using “sudo”.

I encountered this after a new Linux VPS was set up and I was attempting to run the following command (or really any “sudo” command):

Note: The above command allows you to get a root shell, even if you have root SSH access denied.

Resolution

The fix to this was to disable WHM Shell Fork Bomb Protection via the interface. The reason that you may not always see this is if your SSH session doesn’t quite hit the limits of allowed processes and lets you spawn one more for the “sudo” session. In my case, it would not, I just had too many processes.

Reference: https://documentation.cpanel.net/display/ALD/Shell+Fork+Bomb+Protection

Additional Details

To look a little more in depth about how you can tell if this is happening is to look at the ulimits yourself.

Below is an Unprivileged User with Shell Fork Bomb Protection Enabled, notice the Max User Processes capped at 35.

Below is the same user with Shell Fork Bomb Protection Disabled