OOM Killer Terminates Application on RHEL 9

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Kernel out-of-memory killer terminates a critical process under RAM exhaustion.

Environment & Reproduction

Application exits unexpectedly and kernel logs include Out of memory and Killed process lines.

Root Cause Analysis

Memory leak, bursty workload beyond capacity, disabled swap strategy, or cgroup limit misconfiguration.

Quick Triage

Inspect journalctl -k -b and systemd unit resource controls for affected service.

Step-by-Step Diagnosis

Tune application memory usage and set realistic MemoryMax in systemd unit.

Solution – Primary Fix

Increase capacity or adjust swap policy for safer burst handling.

Solution – Alternative Approaches

Set OOMScoreAdjust carefully for critical daemons to reduce kill probability.

Verification & Acceptance Criteria

SELinux is not usually related; prioritize memory telemetry and cgroup controls.

Rollback Plan

Run load tests and verify no new OOM events under expected peak traffic.

Prevention & Hardening

Revert unsafe memory limit changes if they cause immediate service restarts.

Related Errors & Cross-Refs

Establish memory SLO alerts and regression tests for allocation-heavy code paths.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

journalctl -k -b; systemctl show -p MemoryCurrent,MemoryMax; cat /proc/meminfo