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Table of contents
Symptom & Impact
Root filesystem reaches 100 percent usage, services fail to write data, and apt cannot install updates.
Environment & Reproduction
Common on long-running servers with verbose logging and missing retention limits for journald and app logs.
Root Cause Analysis
systemd journal and rotating logs grow without strict caps, consuming critical disk space.
Quick Triage
Check storage with df -h and identify large directories using sudo du -xh /var –max-depth=2 | sort -h.
Step-by-Step Diagnosis
Measure journal footprint with journalctl –disk-usage and inspect hot log files in /var/log.
Solution – Primary Fix
Free space using sudo journalctl –vacuum-time=7d or –vacuum-size=500M, then configure SystemMaxUse in journald.conf.
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Solution – Alternative Approaches
Move application logs to separate volume and use logrotate tuning for aggressive compression and retention.
Verification & Acceptance Criteria
Free disk headroom restored and services write normally. Journal growth stays within configured limits.
Rollback Plan
If over-pruned logs are needed, restore from centralized logging or backup snapshots.
Prevention & Hardening
Enable disk usage alerts and enforce retention policies for both system and application logs.
Related Errors & Cross-Refs
Related failures include ‘No space left on device’ and apt cache write errors.
Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.
View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub โ
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
systemd-journald documentation, logrotate manual, and Ubuntu storage management guide.
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