Troubleshooting 'Bootmgr' Error After Installing Ubuntu Alongside Windows

When you install Ubuntu alongside Windows, a 'Bootmgr' error or the inability to boot into Windows can occur. This can be frustrating, but there are several solutions to this problem. Let's explore common methods to resolve this issue.

One of the first things you can try is to run sudo update-grub from the Terminal in Ubuntu:

Open Terminal in Ubuntu and run the command: sudo update-grub

Alternatively, you can also repair your Windows boot loader. This method is useful if the above solution does not work. Here's how you can do it:

Repair Windows Boot Loader

Boot from your Windows installation media. Press shift F10 on the Setup screen to open a command prompt. Enter the following commands in the command prompt to repair the boot loader:

bootrec /fixmbrbootrec /fixbootbootrec /scanosbootrec /rebuildbcd

Change Boot Order in BIOS

Another method to try is to change the boot order in your BIOS settings. Here are the steps:

While your computer is booting, press the appropriate key (such as Esc or F10) to enter the boot menu. The key to press may vary depending on your computer model. Use the boot menu to navigate to the BIOS settings menu. Find the boot order menu and press Enter where it says “OS boot manager”. Press the F5 or F6 key (again, depending on your BIOS setup) to change the order and make Ubuntu your first preference.

This will allow GRUB to boot first, thereby enabling you to select either Ubuntu or Windows.

Fix Your Boot Sector

At times, your boot sector might need fixing. This can occur due to an update in Ubuntu or corruption in the boot files. To fix your boot sector, you can compress the initramfs as follows:

Modify your GRUB configuration file by changing the value of COMPRESS from lz4 to gzip:

COMPRESSlz4 to COMPRESSgzip

Run the following command to update your initramfs:

sudo update-initramfs -u

Check if this solution works. If it does not, revert the value to the default, which is lz4, and run:

sudo update-initramfs -u

As this solution is mentioned in the Arch Linux forum and other sources, it might help you resolve the issue.

Conclusion

Booting from Ubuntu alongside Windows can sometimes lead to issues such as the 'Bootmgr' error. However, with the right steps, you can resolve these issues and ensure a seamless dual-boot experience. If you have faced similar issues, feel free to share your experiences in the comments below.