RHEL 9: Swap Not Activated at Boot

📖 ~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

Memory pressure causes OOM events because swap remains inactive after reboot.

Environment & Reproduction

Run `swapon –show` and inspect `/etc/fstab` entries for missing or wrong UUIDs.

Root Cause Analysis

Verify util-linux and system tooling are intact for swap management commands.

Quick Triage

Inspect boot target and local filesystem units with `systemctl status local-fs.target`.

Step-by-Step Diagnosis

Use `journalctl -b | grep -i swap` to identify activation errors during startup.

Solution – Primary Fix

Update fstab with correct UUID and run `swapon -a` to validate without reboot.

Solution – Alternative Approaches

Firewall does not affect swap, but maintain standard security posture during maintenance.

Verification & Acceptance Criteria

SELinux generally does not block swap activation for properly labeled partitions.

Rollback Plan

Reboot and verify swap is listed automatically with expected priority.

Prevention & Hardening

Use UUIDs rather than device names in fstab for storage resilience.

Related Errors & Cross-Refs

Restore previous fstab backup if boot warnings appear after edits.

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

Consult `man fstab` and RHEL memory management recommendations.