What is Fix Grub Loading Error and How to Fix Grub Loading Error

David Darlington

May 06, 2026 • Filed to: Windows Computer Solutions • Proven solutions

Part 1. What are GRUB and GRUB Loading Errors?

GRUB stands for Grand Unified Bootloader, which is invoked by your system's BIOS to load kernels and display a boot menu for users to choose from. It's similar to NTLDR or BOOTMGR for Windows, but supports both Windows and Linux kernels, and comes with more features. However, if you haven't configured Grub properly, you will encounter GRUB errors like those described below.

GRUB Error Diagnostic Matrix

Grub Loading Error 15, 17, 21, 22

For Grub Stage 1, there are no error numbers, just "Hard Disk Error", "Floppy Error", "Read Error", or "Geom Error". Hence, if you get an error number, you are probably using Grub Stage 1.5 or Stage 2.0. So, what does the Grub loading error number mean? Let's find out below:

• Grub Loading Error 15: File not found. This error is displayed when the specified file name cannot be found.
• Grub Loading Error 17: Cannot mount selected partition. This error is displayed when the partition requested exists, but the file system type is not be recognized by GRUB.
• Grub Loading Error 21: Selected disk does not exist. This error is displayed if the disk is not recognized by the BIOS in the system.
• Grub Loading Error 22: No such partition. This error is displayed if a requested partition isn't on the selected disk.

What Causes GRUB Loading Errors 15, 17, 21, 22?

Configuring GRB correctly whenever you install Windows and Linux on a computer is important to boot from one of the operating systems successfully. If not done correctly, it may lead to GRUB loading errors, such as errors 15, 17, 21, and 22. The common reasons you are encountering the GRUB loading errors might be:

• The corruption of MBR.
• The configuration of GRUB is improper.
• GRUB is installed at the wrong location.
• GRUB is deleted by accident.

Now that you are aware of what GRUB is, what are the common GRUB Loading Error codes, and the common reasons for these errors to occur, you might be looking for solutions rid of it immediately. So, if you are bothered by the GRUB Loading Error, and want to fix it to keep using your computer seamlessly to deal with your work, read on to get the solutions.

Part 2. How to Fix Grub Loading Error

Here are some simple solutions for all popular Grub loading errors.

Grub Loading Error 15:

If Grub Loading Error 15 is bothering you, you need to make sure that the kernel file exists on your computer. To find out the exact kernel name you need to shut down your PC and then boot it from the Live CD. Then mount /boot on your partition, and then do the following: cd /boot | ls

This will give you the exact name of the kernel file. However, it is also possible that the kernel file is missing from your computer. If that is the case, you can still use the live CD to reinstall the system to get rid of the error.

Grub Loading Error 17:

If you are encountering the Grub Loading Error 17, you should ensure that your root(x,y) settings are right in your Grub.conf. You will need a distribution CD or Live CD to set up Grub as shown below, where (h0,0) means the first hard drive and the first partition on that drive.
sudo grub
root (hd0,0)
setup (hd0)
Exit

1. Boot your computer from a live CD.
2. Execute this command: sudo fdisk –l.
3. You will probably get the following results:
   
   Disk /dev/sdb: 500.1 GB, 500107862016 bytes
   255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 4096 bytes
   I/O size (minimum/optimal): 4096 bytes / 4096 bytes
   Disk identifier: 0x62ff371f
   Device Boot Start End Blocks Id System
   /dev/sdb1 2048 206847 102400 7 HPFS/NTFS/exFAT
   /dev/sdb2 206848 174082047 86937600 7 HPFS/NTFS/exFAT
   /dev/sdb3 174082110 976771071 401344481 f W95 Ext’d (LBA)

Grub Loading Error 21:

To fix Grub error 21, first make sure the disk is correctly connected and detected by the BIOS, then boot the computer from the Ubuntu installation disc.

Now run Command Prompt as an administrator, and enter the following commands:

$sudo -s
#grub
grub> find /boot/grub/stage1 (then cmd will return something like "hd0,0")
grub> root (hd0,0)
grub> setup (hd0)
grub> quit

Grub Loading Error 22:

You can use the Windows Installation Disc to run a Startup Repair and fix MBR.

The Grub loading error generally occurs when Grub is trying to load a non-Windows system. So you can fix the MBR with the Startup Repair option on the Windows Installation Disc and then re-install Grub. For Unix-like systems, use the distribution CD or Live CD. Also, to fix Grub error 22 easily, you can restart the computer and then press "F8" repeatedly until the options appear on your screen.

Now, go back to the menu where there was an option to choose the operating system. Select the "Microsoft Windows Recovery Console.” For this, you may need your Windows installation disc to access the recovery console. Now, enter the number in front of the system drive listed when you are asked to choose the system drive. Next, provide the account password as required. Now, run the command fixmbr and type "y" to confirm the operation. Lastly, press on"exit" and restart your PC.

Pro Tip for 2026: GRUB in the UEFI/GPT Era

While traditional GRUB errors (15, 17, etc.) are common on Legacy BIOS systems, modern PCs use UEFI and GPT partitions. If you encounter boot issues on a 2020+ machine, the error might appear as a "GRUB Rescue" prompt. In these cases, ensure Secure Boot is disabled in your BIOS settings, as it often blocks GRUB from loading Linux kernels on dual-boot systems.

Part 3. How to Recover Data from the Unbootable Computer Caused by GRUB Loading Errors

When your computer encounters GRUB loading errors, you can't boot the computer if the above solutions fail. However, how can I recover data on the computer when this occurs? Don't worry. If this happens, you`ll need a powerful data recovery tool to make sure no important photos, videos, emails, or documents are lost because of the GRUB loading errors.
Recoverit Data Recovery can help you out on this issue. It can create bootable media for you to boot the unbootable computer and recover all kinds of data. Just follow the below steps:

Your Safe & Reliable File Recovery Software

• Recover lost or deleted files, photos, audio, music, emails from any storage device effectively, safely, and completely.
• Supports data recovery from recycle bin, hard drive, memory card, flash drive, digital camera, and camcorders.
• Supports to recover data for sudden deletion, formatting, hard drive corruption, virus attack, system crash under different situations.

Step 1. After launching the Recoverit program, click on data recovery mode. If your windows 10 doesn't start, click the "Recover from Crash Computer" tab, then you will be prompted to click "Start" on the next window that pops up.

Step 2. To create a booting drive, press the mode option. You will be presented with two booting options; the CD/DVD drive and the USB. You can choose any option among the two, then click on the "Create" button to commence the process.

Step 3. You will be prompted with another pop-up window asking to format your selected mode. So if you chose the USB option, tap on the "Format" tab. However, ensure you have relevant data backed up before you continue.

Step 4. The booting process will immediately. However, don't eject the USB flash drive during this process. The next action you need to take will display on the screen or you can view the entire guide.

Step 5. The data recovery process would take a while, so ensure your laptop is plugged into a power source or ensure the battery is fully charged. Upon completion, three data recovery solution steps will be displayed on your screen.

Step 6. Before starting the recovery process, ensure that you have permitted your computer boot sequence to boot from the boot media you created earlier. When that has been done, restart your computer and immediately punch the F12 key.

Note that your BIOS (Basic Input/Output System) key will differ from system to system. Check out how to set the computer to boot from a USB drive.
Step 7. When booting is completed, Recoverit software will start automatically. Now you can copy your hard drive data or start a recovery process on your Windows 10 lost data. We can help you resolve issues regarding lost data on Windows 10.

Closing Words

Now you know what Grub loading error is and how you can fix this problem. Besides, if you lost your important Data Due to GRUB Loading Errors, a professional data recovery tool like Wondershare Recoverit is all you needed to get back your lost or deleted data files.

Summary: Resolving GRUB Boot Failures

• Identify the Code: Match the error number (15-22) to identify if it's a software (config) or hardware (disk) issue.
• Use Live Media: Always keep a Linux Live USB or Windows Installation Media ready for fixmbr or kernel reinstallation.
• Check Connections: For Error 21, verify physical cables or NVMe seating.
• Prioritize Data: If the system is unstable, never attempt a reinstall before using Wondershare Recoverit to back up your critical files.

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