Linux Process Killed (Signal 9)

Linux "Killed" message (SIGKILL, signal 9) means the process was forcefully terminated, usually by the OOM killer or an administrator. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Process terminated with exit code 137 (128 + 9). SIGKILL cannot be caught or handled by the process. Most commonly caused by OOM killer. Process had no chance to clean up or save state. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: OOM killer terminated the process to free memory. Administrator sent kill -9 command. Container runtime killed process exceeding memory limit. Systemd cgroup memory limit exceeded. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Check dmesg for OOM killer messages: dmesg | grep -i "killed process". Check available memory: free -h. Increase available RAM or add swap. Set memory limits in cgroup or container config. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Linux Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.