Ubuntu 20.04 GRUB Rescue Prompt on Startup

📖 ~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 grub rescue prompt instead of Ubuntu.

Environment & Reproduction

Missing normal.mod errors and no standard boot menu.

Root Cause Analysis

Dual-boot and single-boot systems after partition or bootloader changes.

Quick Triage

Broken GRUB core image paths or moved/deleted boot partitions.

Step-by-Step Diagnosis

Identify root and boot partitions from rescue shell and live media.

Solution – Primary Fix

Mount target system, chroot, reinstall GRUB, regenerate config, and reboot.

Solution – Alternative Approaches

Boot menu appears and default Ubuntu entry starts successfully.

Verification & Acceptance Criteria

Back up partition table and avoid abrupt disk layout edits.

Rollback Plan

Escalate for suspected disk failure or repeated bootloader corruption.

Prevention & Hardening

Boot from live USB and restore bootloader from known backup.

Related Errors & Cross-Refs

GRUB manual and Ubuntu live recovery documentation.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

UEFI and BIOS systems require different grub-install targets.