Ubuntu 18.04 Grub Rescue Prompt After Disk Changes

📖 ~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 enters grub rescue and cannot locate normal boot menu.

Environment & Reproduction

Occurs after partition resize, disk migration, or boot order changes.

Root Cause Analysis

GRUB points to invalid root device or missing boot files.

Quick Triage

Identify correct root partition from rescue prompt to boot manually.

Step-by-Step Diagnosis

List GRUB devices, verify /boot path, and inspect partition UUID mapping.

Solution – Primary Fix

Chroot from live media, reinstall grub package, and regenerate grub.cfg.

Solution – Alternative Approaches

Use Boot-Repair utility when manual GRUB reinstall is not practical.

Verification & Acceptance Criteria

Boot menu appears reliably and chosen kernel launches successfully.

Rollback Plan

Reinstate previous bootloader target disk if new path remains unstable.

Prevention & Hardening

Document boot disk mapping before storage maintenance operations.

Related Errors & Cross-Refs

Unknown filesystem, no such partition, grub rescue prompt.

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

GNU GRUB manual and Ubuntu boot recovery documentation.