Disk Full on /var Causes Service and apt Failures

📖 ~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 writes, apt fails, and system logging becomes unreliable due to no space left on device in /var.

Environment & Reproduction

Frequent on Ubuntu 16.04 with small root volumes and verbose logs under /var/log or large apt cache under /var/cache/apt.

Root Cause Analysis

Unbounded log growth, retained journal files, package caches, or runaway application data fills the /var filesystem.

Quick Triage

Run df -h and sudo du -xh /var –max-depth=2 | sort -h to identify top consumers. Check journal size with journalctl –disk-usage.

Step-by-Step Diagnosis

Investigate /var/log, /var/lib, and /var/cache individually, then inspect logrotate configuration and app-specific retention settings.

Solution – Primary Fix

Vacuum journals, clear apt cache with sudo apt clean, rotate/compress oversized logs, and remove stale files safely. Expand volume if growth trend demands it.

Solution – Alternative Approaches

Move heavy data paths to dedicated partitions, centralize logs to remote collectors, or set stricter retention policies for noisy services.

Verification & Acceptance Criteria

At least 20 percent free space remains on /var, critical services restart cleanly, and apt operations succeed.

Rollback Plan

Restore removed data from backup if retention policy was exceeded; revert filesystem changes if migration introduced path breakage.

Prevention & Hardening

Implement disk usage alerts, enforce logrotate for all apps, and set systemd journal limits in journald.conf.

Related Errors & Cross-Refs

Often paired with dpkg interruption, MySQL crash recovery loops, and nginx/apache write permission errors due to full inode or block usage.

Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.

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Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

journalctl(1), logrotate(8), df(1), and capacity management runbooks for Ubuntu servers.