If you are familiar with desktop Linux distributions, maybe you are dual booting with another OS, you may have used at some point in time the grub-customizer program to change the appearance of the GRUB (GRand Unified Bootloader) screen. As a casual Linux user it has been my main way of customizing grub when dual booting Ubuntu with Windows.

I recently switched laptops and Linux distro to Kali with KDE Plasma and fired grub-customizer as usual. I was surprised to find out that it didn't change the grub theme, despite the grub config file literally using the pre-made theme downloaded from Gnome-look.

Long story short, after some mostly unfruitful investigation and digging into the grub files spread around my Kali installation I concluded that 3 main files have to be modified in order to effectively have the theme changed and they are:

• /boot/grub/grub.cfg
• /etc/default/grub
• /etc/default/grub.d/kali-themes.cfg

Grub-customizer did change the first file and updated it with the proper theme.txt location from the theme I downloaded, let's call it myTheme.

After noticing that I manually changed the GRUB_THEME entry in /etc/default/grub with the correct theme location, which was /boot/grub/themes/myTheme/theme.txt.

Then I did the same thing with the /etc/default/grub.d/kali-themes.cfg file and surprise, surprise, it worked!

By this point, the grub theme was fully changed and properly adjusted to my liking. There was a little weird thing happening though, after selecting an OS in the grub screen, no matter if it was Kali or Windows, a default Kali theme image was shown for a second or so, which I wanted to change to not show anything and just load the OS. The workaround to solve this was to load a pure black image (all black pixels) before loading the theme in the /etc/default/grub.d/kali-themes.cfg which I find a little weird because the theme.txt of myTheme already defines a background image. Anyway, the file would contain something like this:

GRUB_BACKGROUND="/boot/grub/themes/kali/black.png"
GRUB_THEME="/boot/grub/themes/myTheme/theme.txt"

And done! The theme got changed and no weird image flashes disturbed my grub screen, so I was happy with the result 😊.