Ubuntu 18.04 LTS – disk full under /var/log causes service failures – Fix & Prevention

📖 ~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

Services crash or refuse startup when root filesystem reaches 100 percent.

Environment & Reproduction

Ubuntu 20.04 host with verbose logging and weak retention controls.

Root Cause Analysis

Unbounded logs, core dumps, or rotated files consume critical disk capacity.

Quick Triage

Run df -h and du scans under /var/log to locate top consumers.

Step-by-Step Diagnosis

Identify runaway logs, journal growth, and failed rotation tasks.

Solution – Primary Fix

Free space safely, tune journald limits, and enforce logrotate policies.

Solution – Alternative Approaches

Offload logs to centralized storage and reduce local retention.

Verification & Acceptance Criteria

Sustained free space threshold is restored and services remain healthy.

Rollback Plan

Recover archived logs from backup if audit requirements demand restoration.

Prevention & Hardening

Alert on filesystem usage and validate rotation in routine health checks.

Related Errors & Cross-Refs

Database corruption and package failures can occur when disk is exhausted.

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

Ubuntu journald and logrotate administration documentation.