Is it possible to edit grub.cfg?

I wish to change a menu entry in grub.cfg, for example:

From

### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu is wonderful'

To

### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu is world famous'

Solution 1:

Edit /etc/grub.d/10_linux instead and run sudo update-grub when you are done. This is a more reliable method, otherwise every time you upgrade to a new kernel your /boot/grub/grub.cfg will be overwritten and you will lose your changes.

Or you can use Grub Customizer. To install it:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer

Solution 2:

How to do it from an emulator to learn how GRUB works, without the risk of breaking anything.

• create a Multiboot hello world main.elf file. GRUB knows how to boot those files (GRUB also knows how to boot the Linux kernel, even though it is not Multiboot)

• create a iso/boot/grub/grub.cfg file containing:

  menuentry "main" {
      multiboot /boot/main.elf
  }
  

  Place main.elf under iso/boot/

• Generate an image and run it:

  grub-mkrescue -o main.img iso
  qemu-system-x86_64 -hda main.img
  

This will boot into GRUB, and you will see an entry called main.

Now edit grub.cfg like menuentry "newmain", and upon a reboot the new option name is newmain. So your change would work.

I have posted the exact code for this example at: https://github.com/cirosantilli/x86-bare-metal-examples/tree/d217b180be4220a0b4a453f31275d38e697a99e0/multiboot/hello-world

As others said, don't do it in practice, since that is normally an output file and will get overwritten on update-grub.