How to change "--class" in GRUB2 boot loader?

Teso · 07-31-2020, 05:23 PM

Hello,
how do i change the "-class" in the GRUB2 boot loader?
The "--class" shows wrong pictures, operating systems are not correctly recognized by the GRUB2. I would also like to insert a picture (--class) in the submenu, BIOS/UEFI-menu and remove some of the "--class" entries.

Code:

menuentry "Kubuntu 20.04 - GNU/Linux (kernel-5.4.0.42-generic)" --class ubuntu --class gnu-linux --class gnu --class os

ondoho · 08-01-2020, 05:35 AM

Looking at this page (did you?), "class" is mentioned several times.
What I took away after a few minutes:

grub-mkconfig creates the grub menu. It either has direct options to change its behaviour or can be influenced through variables in /etc/default/grub
it's possible to override which images are displayed by placing appropriate files in "grub/themes/icons" (my guess: /boot/grub/themes/icons)

Teso · 08-01-2020, 06:08 AM

Thank you,
I have this GNU GRUB Manual 2.04 in .pdf.
I don't want to learn GRUB I just want to add or change this one command (class). That's why I'm asking here.

---EDIT---

As I understand it, I have to add this line:

Code:

menuentry title [--class=class …] [--users=users] [--unrestricted] [--hotkey=key] [--id=id] { command; … }

to the "/etc/default/grub" and edit it to get the variable in "/boot/grub/grub.conf" after "update-grub".
What do I have to change now to get the desired result?
I have "Kubuntu OS" and I liked that the right picture is shown in the menu (kubuntu.png).

Code:

menuentry kubuntu [--class=kubuntu …] { command; ???? }

ondoho · 08-01-2020, 12:13 PM

Quote:

Originally Posted by Teso

As I understand it, I have to add this line:

Code:

menuentry title [--class=class …] [--users=users] [--unrestricted] [--hotkey=key] [--id=id] { command; … }

to the "/etc/default/grub" and edit it to get the variable in "/boot/grub/grub.conf" after "update-grub".

No.
You don't edit /boot/grub/grub.cfg manually.
Please check all the variables you can add to /etc/default/grub.
Also check the man pages for grub-mkconfig and/or grub2-mkconfig and/or update-grub.

I don't use grub anymore, so I can't check myself.

berndbausch · 08-01-2020, 10:41 PM

Quote:

Originally Posted by ondoho

No.
You don't edit /boot/grub/grub.cfg manually.
Please check all the variables you can add to /etc/default/grub.

I believe that you have to edit grub.cfg manually to change the --class options. Or at least the files in /etc/grub.d. I didn't see anything in /etc/default/grub that impacts class.

Depending on the distro and the type of BIOS, grub.cfg might not be in /boot/grub.

Teso · 08-26-2020, 05:17 PM

Quote:

Originally Posted by berndbausch

I believe that you have to edit grub.cfg manually to change the --class options. Or at least the files in /etc/grub.d. I didn't see anything in /etc/default/grub that impacts class

Yes that's right. The problem is that after every kernel upgrade

Code:

update-grub

is executed, the grub.cfg gets reseted and I have to edit the grub.cfg again.
After executing

Code:

update-grub

I would like to have the right images at the right place automatically.

colorpurple21859 · 08-26-2020, 05:45 PM

Maybe edit /etc/grub.d/10_linux or the one that has theme in the name. This file may get replaced if there is an update to the grub package.

colorpurple21859 · 08-26-2020, 08:02 PM

scatch my other post, edit or add this line to /etc/default/grub:

GRUB_DISTRIBUTOR="Kubuntu"

run update-grub

ondoho · 08-28-2020, 09:57 AM

Quote:

Originally Posted by Teso

Yes that's right. The problem is that after every kernel upgrade

Code:

update-grub

is executed, the grub.cfg gets reseted and I have to edit the grub.cfg again.
After executing

Code:

update-grub

I would like to have the right images at the right place automatically.

That's because you're not supposed to edit that file directly.
I believe it even says so at the top.
/etc/default/grub is what you want to edit.

elcore · 08-29-2020, 01:15 AM

Quote:

Originally Posted by ondoho

That's because you're not supposed to edit that file directly.

Some distributions don't update-grub on kernel upgrade, but instead simply symlink the new kernel where the old one used to be.
In which case, there's nothing wrong with editing that file directly. It'll still work as a static file just like menu.lst or lilo.conf.