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I installed a mainline kernel for testing purposes. I would like to set grub to boot from the older kernel by default.

I know I can set the GRUB_DEFAULT=0 setting for the first page of grub but how do I set it to boot by default from one kernel in the second page (Advanced page)?

I would prefer doing this without installing other software (ex. grub-customizer).

Related Questions:
How do I set Windows to boot as the default in the boot loader?
How do I change the grub boot order?

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1  
@belacqua: It is not a duplicate. This question is about setting an older kernel that is not present in grub's first page of options as default. – To Do Nov 13 '12 at 13:14
    
It seems like this case should be covered in the earlier questions, even if the method needs to be update for 12.10, older kernels, etc.. – belacqua Nov 13 '12 at 15:26
2  
The question's use case is different, and the answer is very specific in a way that doesn't apply to the other claimed duplicates. I came here to solve this particular problem; not to change the boot order; nor to boot Windows. +1 for "not a duplicate". – Robie Basak Mar 16 '15 at 14:09
up vote 89 down vote accepted

First, make a backup copy of /etc/default/grub. In case something goes wrong, you can easily revert to the known-good copy.

sudo cp /etc/default/grub /etc/default/grub.bak

Then edit the file using the text editor of your choice (ie. gedit, etc.).

sudo gedit /etc/default/grub

Find the line that contains GRUB_DEFAULT - this is what you'll want to edit to set the default. You must know the full name of the kernel you want - e.g. Ubuntu, with Linux 3.13.0-53-generic - along with the full name of the "advanced menu" - e.g. Advanced options for Ubuntu.

You then combine those two strings with > and set GRUB_DEFAULT to them as: GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 3.13.0-53-generic" (including quotes).

Save it, then build the updated grub menu.

sudo update-grub

See also: GNU GRUB Manual 2.02

Note: There is a method utilizing numbers to access kernels and menus but this is not recommended as it is unreliable when kernel updates occur.

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18  
Using a numeric value can be problematic when updates occur. It's better to use a text default, ie: GRUB_DEFAULT="Previous Linux versions>Ubuntu, with Linux 3.2.0-18-generic" – Bealer Jul 4 '13 at 16:45
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One can use sudo grub-mkconfig | less to see all of the possible options – Nitz Feb 17 '15 at 20:55
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This is a good solution, but even better is to open a /boot/grub/grub.cfg and there you will see all the manuentry and all the submenus. If you edit them, you can easy set the default ones, even change the Titles of the options in the grub list when restarting a computer. – Aleks Apr 21 '15 at 21:03
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It is definitely useful to examine /boot/grub/grub.cfg to determine the exact names to use. But do not change this file as it will be automatically regenerated by update-grub, including on updating packages. – Robie Basak May 19 '15 at 16:36
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The formatting for GRUB_DEFAULT is slightly outdated (since at least Ubuntu 14.04.2). Running update-grub I encountered a warning: Please don't use old title Previous Linux versions>Ubuntu, with Linux 3.13.0-53-generic for GRUB_DEFAULT, use Advanced options for Ubuntu>Ubuntu, with Linux 3.13.0-53-generic (for versions before 2.00) or gnulinux-advanced-b0ce60c3-184c-453b-af59-419b56a2584f>gnuli‌​nux-3.13.0-53-generi‌​c-advanced-b0ce60c3-‌​184c-453b-af59-419b5‌​6a2584f (for 2.00 or later) – Wumms Jul 3 '15 at 21:32
up vote 6 down vote

Now that an Advanced menu is default in Ubuntu, you'll need to select it before the kernel you want using the > character.

Set e.g.:

GRUB_DEFAULT="1>7"

in /etc/default/grub and re-run sudo update-grub.

It is important to note that for the GRUB menu entries numbering starts with 0. Therefore the 1 above points to the Advanced menu. As a precaution, you may want to initially set GRUB_TIMEOUT=5. Some may be unable to access GRUB by hitting a key at boot time. This is a safety net in case you accidentally point to something like Memory test instead. It is also necessary to include the above numbers in quotes. It will not work otherwise.

I tested on 16.04 LTS.

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