earlyoom - A Simple OOM Killer

Ubuntu Tutorials - Herong's Tutorial Examples

∟earlyoom - A Simple OOM Killer

This section provides a tutorial example on how to install 'earlyoom' to prevent OOM (Out Of Memory) freeze.

What Is "earlyoom"? - "earlyoom" is a simple, stable and tiny OOM (Out Of Memory) killer written in C language.

Some how there is no OOM killer included in my Ubuntu computer. When I use Firefox and open multiple tabs to browse the Internet, the system freezes frequently. The only way to free the computer is to press "Alt-PrtSc-S.U.B" for a reboot.

My computer only has 4 GB of RAM, which runs into OOM (Out Of Memory) when Firefox launches multiple processes to support Web browsing activities. By default, Ubuntu should run an OOM killer in the background to detect OOM and kill some running processes to prevent system freeze.

But for some reason, there is no OOM killer running on computer. So I installed "earlyoom" as described below.

1. Install and run "earlyoom".

herong$ sudo apt install earlyoom

herong$ sudo systemctl enable --now earlyoom

2. Make sure that "earlyoom" is running.

herong$ sudo systemctl status earlyoom

● earlyoom.service - Early OOM Daemon
   Loaded: loaded (/lib/systemd/system/earlyoom.service; enabled; ...
   Active: active (running) since Sun 2025-12-14 16:27:41 EST; ...

3. Stress test the system by running Firefox with many tabs open to play YouTube in each of them.

4. A few moments later, one of Firefox tabs crushed. "earlyoom" killed its sub-process.

5. Search the system log file. I see the OOM killing message.

 
herong $ grep oom /var/log/syslog'
  ...
  ubuntu earlyoom[10287]: Out of memory! avail: 345 MiB < min: 362 MiB
  ubuntu earlyoom[10287]: Killing process 11260 Isolated Web Co