Ubuntu 18.04 LTS – CPU spikes caused by runaway logrotate postrotate script

📖 ~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

Periodic CPU saturation aligns with logrotate runs and affects service responsiveness.

Environment & Reproduction

Appears when custom postrotate scripts loop, block, or restart heavy services repeatedly.

Root Cause Analysis

Faulty postrotate logic triggers excessive process spawning or repeated service reloads.

Quick Triage

Correlate CPU spikes with cron schedule and inspect recent logrotate execution logs.

Step-by-Step Diagnosis

Review logrotate config, postrotate scripts, and process trees during spike windows.

Solution – Primary Fix

Repair postrotate script logic, add idempotency guards, and limit expensive actions.

Solution – Alternative Approaches

Move heavy post-rotation tasks to controlled maintenance jobs with rate limits.

Verification & Acceptance Criteria

CPU usage remains stable across several logrotate cycles with expected service behavior.

Rollback Plan

Restore previous rotation policy if updated scripts produce new operational side effects.

Prevention & Hardening

Test rotation hooks in staging and enforce script linting and timeout controls.

Related Errors & Cross-Refs

run-parts script failures and recurring high CPU cron intervals.

Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.

View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

logrotate scripting guidance and Linux service reload best practices.