📖 ~1 min read
Table of contents
Symptom & Impact
Memory pressure escalates quickly and OOM events occur because configured swap space is not enabled.
Environment & Reproduction
Common after disk migration or UUID changes where /etc/fstab swap entry no longer matches actual device.
Root Cause Analysis
Swap activation fails when device path, UUID, permissions, or encryption mapping does not resolve at boot.
Quick Triage
Check free -h and swapon –show, then validate fstab entry without rebooting repeatedly.
Step-by-Step Diagnosis
Inspect blkid output, verify swap signature, and review journalctl boot logs for systemd swap unit failures.
Solution – Primary Fix
Recreate or relabel swap device as needed, update fstab with correct UUID, and activate with swapon -a.
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Solution – Alternative Approaches
Deploy swapfile with secure permissions or tune vm.swappiness to match workload behavior.
Verification & Acceptance Criteria
Swap appears in swapon output across reboot and memory pressure no longer triggers immediate OOM kills.
Rollback Plan
Restore previous swap configuration or revert to known-good image if new layout causes boot regressions.
Prevention & Hardening
Track storage UUID changes, validate fstab in change workflows, and monitor swap availability continuously.
Related Errors & Cross-Refs
Often surfaces with OOM killer incidents and high-memory service startup failures.
Related tutorial: View the step-by-step tutorial for Debian 13.
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Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
swapon and fstab man pages, Debian memory management docs, and kernel virtual memory tuning references.
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