how to change GRUB timeout?

[Bammede]

How to change GRUB timeout, so it is different from the OS base image, but leave anything else untouched?

Latest Fedora uses: grub.cfg

[notnotno]

This is how I do it:

sudo echo "set timeout=2" | sudo tee -a /boot/grub2/user.cfg

[Bammede]

where do you put it in Bluebuild project?

[xynydev]

To run arbitrary lines of shell script you can use the snippets in the script module: https://blue-build.org/reference/modules/script/#example-configuration

type: script
snippets:
  - "sudo echo "set timeout=2" | sudo tee -a /boot/grub2/user.cfg"

[notnotno]

It's true that you can add code snippets to your recipe that way, but this particular command is not something that would go in the recipe.

You need to run it from a terminal after you boot.

[xynydev]

Ah, I'm not familiar enough with grub configs to know if they can be customized at build-time. Good to know this at least.