Ubuntu 18.04 LTS – Common Problem 025 – Diagnosis and Fix

📖 ~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

System boots into emergency mode with failed mount units, delaying service availability.

Environment & Reproduction

Ubuntu 18.04 after disk replacement, UUID changes, or manual edits to /etc/fstab.

Root Cause Analysis

Invalid or stale UUID/device path in fstab causes systemd mount timeout and boot interruption.

Quick Triage

From emergency shell, run lsblk -f and journalctl -xb to find failing mount entries.

Step-by-Step Diagnosis

Compare fstab UUIDs against blkid output and validate options for each filesystem type.

Solution – Primary Fix

Edit /etc/fstab to correct UUIDs or add nofail where appropriate, then run mount -a to validate before reboot.

Solution – Alternative Approaches

Use systemd device dependencies or automount options for non-critical removable volumes.

Verification & Acceptance Criteria

System boots normally without emergency shell and all required filesystems mount successfully.

Rollback Plan

Restore previous fstab backup from rescue media if new mount configuration fails.

Prevention & Hardening

Require peer review for fstab changes and test with mount -a in maintenance sessions.

Related Errors & Cross-Refs

Dependency failed for Local File Systems, Timed out waiting for device, and emergency.target reached.

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

man fstab, systemd.mount documentation, and Ubuntu recovery mode procedures.