Fixing GRUB Syntax Errors Caused by Grub Customizer

You've updated your system, and suddenly you're greeted with a cryptic GRUB error message:

This error can be frustrating, especially when you haven't manually edited any GRUB configuration files. This blog post will guide you through identifying the source of this problem and how to fix it.

The Source of the Problem: Grub Customizer

In many cases, the culprit behind these GRUB syntax errors is a tool called Grub Customizer. While it offers a graphical interface to manage your GRUB bootloader, it can sometimes cause problems, especially after system updates.

Grub Customizer works by replacing the standard GRUB configuration scripts in /etc/grub.d/ with its own "proxy" scripts. These proxy scripts then call a binary named grubcfg_proxy to apply the customizations. This can lead to a fragile configuration that breaks when other parts of the system are updated.

How to Detect the Source of the Problem

You can confirm if Grub Customizer is the cause of your issues by inspecting the /etc/grub.d/ directory. Open a terminal and run:

If you see files with _proxy in their names (e.g., 10_linux_proxy, 30_os-prober_proxy) and directories like backup, bin, and proxifiedScripts, it's a strong indication that Grub Customizer has modified your GRUB configuration.

You might also find a script like this in /etc/grub.d/10_linux_proxy:

This non-standard script is a clear sign of Grub Customizer's intervention.

The Approach and Solution

The most reliable way to fix this issue is to completely remove Grub Customizer and restore your GRUB configuration to its default state. This will remove any customizations you've made with the tool, but it will give you a stable and working bootloader.

Here are the steps to follow:

1. Purge Grub Customizer

First, you need to completely remove the grub-customizer package and its configuration files. Run the following command:

2. Reinstall GRUB

Next, reinstall the GRUB package to ensure all the original scripts are restored in /etc/grub.d/.

Note: This command is for systems using a traditional BIOS or CSM. If you are using UEFI, you might need to install grub-efi-amd64 or a similar package depending on your architecture.

3. Update GRUB

Finally, regenerate the grub.cfg file with the restored, standard scripts. This command will also run os-prober to detect other operating systems like Windows and add them to the boot menu.

After running these commands, your GRUB configuration should be back to a clean, working state, and the syntax errors should be gone.

Conclusion

Grub Customizer can be a convenient tool, but it can also lead to unexpected issues. If you encounter GRUB errors after using it, the best solution is often to remove it and revert to the standard GRUB configuration. By following the steps in this guide, you can quickly resolve these errors and get your system booting correctly again.