The bootloader is a critical component of any operating system and is responsible for loading the operating system into memory during the system boot process. One of the most commonly used bootloaders in the Linux ecosystem is GRUB (Grand Unified Bootloader).

Although GRUB is reliable and robust, users may encounter issues that may prevent their system from booting properly. Let's take a look at some common GRUB-related bootloader problems and consider step-by-step solutions for solving them.

Understanding the GRUB Bootloader

Before diving into the troubleshooting process, it's essential to understand how GRUB functions. GRUB uses configuration files and a two-stage boot process to initiate the operating system. The primary configuration file is typically located at /boot/grub/grub.cfg, which contains information about the available kernels and boot options.

So all the rules you specify in this grub.cfg file will determine your rules on how to boot. In this case, this should be the first point you will look for to solve the problems you may encounter.

Common GRUB Bootloader Problems

A broken hard drive

GRUB causes many errors, especially on dual-boot systems. For example, if you're a Windows user and want to dual-boot a Linux distribution alongside Windows, GRUB lists all the operating systems installed on your PC, and you choose from them.

When you install Linux with Windows, you are relatively less likely to encounter errors.

However, in the opposite case, that is, if you install Windows alongside Linux, GRUB can throw you into errors. It will be very helpful for you to learn about some of the most common mistakes you may encounter in this regard.

Remember, this is risky if you are not an expert in this field and have no experience with any boot technologies. Any small mistake you make may cause you to be unable to access your system. So make sure you have a backup of everything and don't hesitate to seek professional help if needed.

1. Error: No Such Partition

You usually see this error when GRUB cannot find the specified partition or drive. Disk changes, bad partitioning, or corruption can cause this error to appear.

To solve this, you must enter GRUB's command-line interface (CLI) from the GRUB menu. Then use the following command to list the partitions and drives that GRUB can use:

        grub> ls
# Example Output
(hd0) (hd0,msdos1) (hd1) (hd1,msdos2) ...

You need to identify the partition containing the boot directory and the Linux kernel. For example, if hd0,msdos1, set the correct root partition, using that:

        grub> set root=(hd0,msdos1)

Finally, load the kernel and the initial RAM disk and boot the system. However, the expression /dev/sda1 may be different for you. You can enter the disk space where the Linux kernel is located. This can usually be expressions like sda1, sdb1:

        grub> linux /vmlinuz-version root=/dev/sda1
grub> initrd /initrd-version
grub> boot

2. Error: File Not Found

This error occurs when GRUB cannot find essential boot files specified in grub.cfg. It might happen after kernel updates or if the configuration file is corrupted.

To fix this, boot into GRUB's CLI again and use the ls command to find the correct partition as shown in the previous example. Then, set the root partition and load the kernel and initial RAM disk:

        grub> set root=(hd0,msdos1)
grub> linux /boot/vmlinuz-version root=/dev/sda1
grub> initrd /boot/initrd-version
grub> boot

3. Error: Unknown Filesystem

This error indicates that GRUB cannot recognize the filesystem used for the boot partition. It may happen if you have changed the filesystem type or if the necessary filesystem drivers are missing.

To address this, first, determine the filesystem of the boot partition:

        grub> ls
(hd0) (hd0,msdos1) (hd1) (hd1,msdos2) ...
grub> ls (hd0,msdos1)/

Replace hd0,msdos1 with your boot partition. Then, load the required modules for the detected filesystem:

        grub> insmod ext2

Make sure to use the appropriate filesystem module for your system. After that, set the root partition, load the kernel, and boot the system:

        grub> set root=(hd0,msdos1)
grub> linux /boot/vmlinuz-version root=/dev/sda1
grub> initrd /boot/initrd-version
grub> boot

Reinstalling GRUB to Fix the Errors

If the bootloader problems persist, reinstalling GRUB may be the best solution. You can do this using a live Linux USB/DVD to access the system. First, boot into the live environment and open a terminal. Next, identify the root partition of your Linux installation using lsblk or fdisk.

        lsblk
lsblk command output on linux

For this example, let's take sdb1 as the root partition. Next, you must mount the relevant partitions. To do this, edit the commands below and run them one by one:

        sudo mount /dev/sdb1 /mnt
sudo mount /dev/sdb2 /mnt/boot (if a separate boot partition exists)
sudo mount --bind /dev /mnt/dev
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys

Now, chroot into your system:

        sudo chroot /mnt

Finally, reinstall GRUB to the MBR (Master Boot Record) of your primary disk:

        exit
sudo umount /mnt/dev/pts /mnt/dev /mnt/proc /mnt/sys /mnt/boot /mnt
sudo reboot

There Is Another Method to Solve GRUB Errors!

If all these commands seem like too much and you're not sure you can keep things under control, there's a user-friendly tool you can use. Boot Repair will help you fix many problems with your GRUB problems with just a few clicks. First, make sure this tool is installed on your system:

For Ubuntu or Linux Mint:

        sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install boot-repair

For Fedora:

        sudo dnf install boot-repair

For Arch Linux:

        yay -S boot-repair

For other distributions, you may find Boot Repair in their respective package repositories or available as a standalone package from the official website.

Step 1: Launching Boot Repair

Once Boot Repair is installed, you can start it from the terminal or search for it in your system's application launcher. If you prefer the terminal, run the following command:

        boot-repair

Boot Repair will now launch, and after a short analysis of your system's boot configuration, it will display the main interface.

welcome screen of boot-repair tool

Step 2: Using Boot Repair to Fix GRUB Errors

The Boot Repair interface is designed to be user-friendly and straightforward. Here are the key steps to perform the repair:

  1. Identifying the boot repair recommended repair option: In most cases, Boot Repair will automatically identify the issues and provide a recommended repair option. This option is displayed in the interface and is typically the best course of action to fix GRUB errors. Click the recommended repair button to proceed.
  2. Understanding repair actions: Boot Repair will now execute the recommended repair actions, which might involve reinstalling GRUB, updating configurations, or restoring the boot sector.
  3. Implementing repair actions: If Boot Repair requires your confirmation for certain repair actions, a pop-up will prompt you to proceed. Always review the actions before confirming. In most cases, it is safe to proceed as Boot Repair is specifically designed to handle these situations.
  4. Completing the repair process: After the repair actions have been successfully executed, Boot Repair will display a message indicating the successful completion of the process. Reboot your system to test if the GRUB errors have been resolved.

If you have no idea here and this is a worrying process for you, it makes sense to follow the recommended repair.

Don’t Forget to Back Up Your System

Dealing with bootloader problems can be daunting, but armed with the right knowledge and troubleshooting steps, you can resolve issues related to the GRUB bootloader effectively.

By understanding the common errors and utilizing GRUB's powerful command-line interface, users can regain control of their Linux systems and ensure smooth and uninterrupted boot processes.

Remember, always double-check commands and make backups before attempting any fixes to avoid potential data loss.