How to Fix GRUB Boot Issues in Linux: A Complete Guide

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If your Linux system fails to boot and stops at the GRUB command line (grub> or grub rescue>), it usually indicates a bootloader failure. Many users mistakenly reinstall GRUB or even the entire operating system, but in most cases, this issue can be fixed without reinstallation.

📌 In this guide, you’ll learn:
✅ Why your system is stuck at grub> or grub rescue>
✅ How to manually boot your system using GRUB commands
✅ Step-by-step methods to restore the GRUB bootloader
✅ Best practices to prevent GRUB-related issues

🛑 1. Understanding the GRUB Boot Failure

When GRUB fails, your system may stop at one of two different command-line interfaces:

1️⃣ grub> Prompt (GRUB Normal Mode)

• GRUB is loaded, but its configuration is missing or incorrect.
• Common Causes:
  • Incorrect bootloader configuration
  • Kernel or initrd.img file missing from /boot

You might see an error like:

error: you need to load the kernel first.

2️⃣ grub rescue> Prompt (GRUB Rescue Mode)

• GRUB cannot find its core files or cannot access the disk.
• Usually occurs when GRUB files are missing or the disk is unreadable.
• Common Causes:
  • GRUB installation is corrupted
  • Filesystem errors on /boot or root partition
  • Disk partition UUIDs changed after a disk replacement

🔍 2. Diagnosing the Issue

Before fixing GRUB, identify the exact cause of the problem.

🔹 Step 1: Check Available Partitions

From the grub> or grub rescue> prompt, list detected partitions:

ls

📌 Example Output:

(hd0) (hd0,msdos1) (hd0,msdos2)

Try listing files in /boot:

ls (hd0,msdos1)/boot/

✅ Expected Output:
You should see vmlinuz, initrd.img, and grub directory.

If the /boot partition is missing or inaccessible, the issue is likely a corrupt filesystem or incorrect partition settings.

🛠️ 3. Fixing GRUB from the grub> Prompt

If your system stops at grub>, it means GRUB is functional, but its configuration is missing or incorrect.

🔹 Step 1: Manually Boot Linux from GRUB

1️⃣ Set the correct boot partition (adjust (hd0,msdos1) as needed):

set root=(hd0,msdos1)
set prefix=(hd0,msdos1)/boot/grub
insmod normal
normal

2️⃣ If GRUB loads but shows "You need to load the kernel first," manually boot Linux:

linux (hd0,msdos1)/boot/vmlinuz-$(uname -r) root=/dev/sda1 ro
initrd (hd0,msdos1)/boot/initrd.img-$(uname -r)
boot

✅ Solution: If this works, the issue is likely a missing or broken grub.cfg file.

🔹 Step 2: Restore the GRUB Bootloader

If you can boot manually, permanently fix GRUB:

1️⃣ Boot into your Linux system
2️⃣ Reinstall GRUB:

grub-install /dev/sda
grub-mkconfig -o /boot/grub/grub.cfg
update-grub  # Debian-based systems

3️⃣ Reboot and verify the issue is resolved.

🛠️ 4. Fixing GRUB from the grub rescue> Prompt

If your system drops to grub rescue>, it means GRUB is unable to locate its core files.

🔹 Step 1: Locate the Boot Partition

Run:

ls

Try different partitions until you find /boot/grub:

ls (hd0,msdos1)/boot/grub

🔹 Step 2: Load the Correct GRUB Modules

Once you've identified the correct partition, run:

set root=(hd0,msdos1)
set prefix=(hd0,msdos1)/boot/grub
insmod normal
normal

This should bring you back to the normal GRUB menu.

🔹 Step 3: Reinstall GRUB

Once you boot into Linux, reinstall GRUB:

grub-install /dev/sda
update-grub
reboot

📌 If the root filesystem is corrupted, repair it first:

fsck -y /dev/sda1

🛡️ 5. Preventing Future GRUB Issues

To avoid bootloader failures, follow these best practices:

✅ Backup the GRUB configuration regularly

cp /boot/grub/grub.cfg /boot/grub/grub.cfg.bak

✅ Ensure correct partition UUIDs in /etc/fstab

blkid
cat /etc/fstab

✅ Avoid forced power shutdowns Use:

shutdown -h now

instead of unplugging power.

✅ Check for disk errors periodically

fsck -n /dev/sda1

✅ Be cautious when updating the kernel If upgrading the kernel, make sure GRUB updates correctly:

update-grub

📊 6. Summary

💬 Join the Discussion!

Have you ever faced GRUB boot issues in Linux?
How did you fix them?

💬 Share your experiences in the comments below! 🚀

👉 If you're troubleshooting Linux filesystem errors, check out: How to Recover Files from the Linux lost+found Directory