# Killed / Out of memory: Killed process (Linux OOM killer)

**Code:** `OOM killer` · **Category:** Linux · **Seen on:** Linux

The kernel ran out of memory and killed a process to recover — the program just prints “Killed” (exit code 137).

## Meaning

When RAM and swap are exhausted, the OOM killer picks the biggest process and sends SIGKILL. There’s no stack trace; the evidence is in the kernel log. Small VPSs without swap hit this during builds (npm, Composer, webpack) and database spikes.

## Common causes

- Server has too little RAM / no swap
- Memory-hungry build steps (webpack, tsc, Composer)
- Memory leak in a long-running process
- Too many worker processes (PHP-FPM, Gunicorn) for the RAM

## Quick fix

1. Confirm: `dmesg -T | grep -i -E "killed process|oom"`
2. Add swap on small servers
3. Reduce workers / limit process memory
4. Build on CI instead of the production server

## Detailed fix by platform

### Linux

1. Add a 2 GB swap file:

```bash
sudo fallocate -l 2G /swapfile && sudo chmod 600 /swapfile
sudo mkswap /swapfile && sudo swapon /swapfile
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
free -h
```


## How to diagnose

1. **Kernel log** — dmesg / journalctl -k for OOM entries
2. **Victim** — Which process and how big?
3. **Capacity** — RAM, swap, worker counts

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Source: [WhatIsMyError](https://whatismyerror.com/errors/linux/killed-oom-killer)