How to install a custom grub theme?

[ImGGAAVVIINN]

Describe the question

I want to install a custom grub theme on my custom distro, but I don't know how to do it

What you have tried

I have tried to edit /etc/default/grub to change the grub theme but it didn't apply after I installed the distro

Expected behaviour

A clear and concise description of what you expected to happen.

The custom grub theme should be applied when booting up after I installed the distro onto a pc

[PJ-Singh-001]

The Ubiquity installer overwrites your changes to /etc/default/grub.
This is why your changes are not reflected in the installed OS.

Therefore, you need to tell Ubiquity to replace the Ubiquity-modified grub file with your custom grub file.

1. Make your changes to the default grub file as you did before.

   /etc/default/grub
   

2. Make the same changes to this "backup" grub file, as well.

   /usr/share/grub/default/grub
   

3. Instruct Ubiquity to apply the custom grub file (from /usr/share/grub/default/grub).

   On the Options page, Preseed tab, select the ubuntu.seed file, and add the following lines at the end:

   This preseed command will be executed by Ubiquity once it has finished installing your OS.

   # (a) Generate /boot/grub/grub.cfg using the customized version of /etc/default/grub.
   # (b) Revert the customized version of /etc/default/grub after it has been overwritten.
   ubiquity ubiquity/success_command string \
       in-target bash -c 'update-grub'; \
       in-target bash -c 'cp /usr/share/grub/default/grub /etc/default/grub';
   

(I assume the new Subiquity installer in Ubuntu 23.04 does the same thing as Ubiquity, but the above may not work for Subiquity, because Ubuntu 23.04 no longer uses preseed files).