Renaming GRUB Entries - Grub Customizer Does Not Rename

I have installed two Ubuntu 20.04 OSes in two different partitions of an SSD in my computer. For ease of use though I want to rename all the GRUB entries.

I initially used the Grub Customizer, but although in the GUI the changes seemed to have taken place, when I restarted they had not. Meanwhile, in the Grub Customizer the changes keep appearing.

My first question is why Grub Customizer does not seem to work, even though it lists the changed I have made, and my second question is, generally, how can I rename all the GRUB entries?

I know there are a lot of similar questions as mine, but all give different options, while at the same time most suggesting the Grub Customizer.

Solution 1:

You've likely using grub-customizer on the wrong OS, ie. the OS that doesn't control the booting.

As you have two OSes (Ubuntu's) installed; each will have it's own grub, one will be used; the other will be ignored. You made the changes I bet in the one that is ignored. Boot your other OS and you'll see there what your machine actually uses (OR use grub-install on the one you made the changes already to to make it take over ownership of grub).

The last installed OS is usually the owner of the boot process; unless changed using grub-install or equivalent command.