Set "older" kernel as default grub entry

Question

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?

Answer 1

First, make a backup copy of /etc/default/grub. If 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 (e.g. gedit, etc.).

sudo -H 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 or more specifically section 15.1.0 on setting the default.

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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.

Answer 2

The best solution for me was to set (in /etc/default/grub):

 GRUB_DEFAULT=saved
 GRUB_SAVEDEFAULT=true

With this settings the last selected value is kept for the next boot. If you have a new kernel you don't have to edit your config.

Don't forget to re-run sudo update-grub

The solution is from reading: info grub-mkconfig

Answer 3

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.

Answer 4

To be able to set which boot option to use as default you need to know what there is... so:

To display the menu entries without actually booting, try something like:

$ lsb_release -s -rdc
Ubuntu 16.04.4 LTS
16.04
xenial

$ update-grub --version
grub-mkconfig (GRUB) 2.02~beta2-36ubuntu3.17

$ grep -Ei 'submenu|menuentry ' /boot/grub/grub.cfg | sed -re "s/(.? )'([^']+)'.*/\1 \2/"
menuentry  Ubuntu
submenu  Advanced options for Ubuntu
    menuentry  Ubuntu, with Linux 4.4.0-34-generic
    menuentry  Ubuntu, with Linux 4.4.0-34-generic (upstart)
    menuentry  Ubuntu, with Linux 4.4.0-34-generic (recovery mode)
menuentry  System setup

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Addition, for 24.04, 2024-05-29 - / using zfs (I guess revert entries are related to zfs!)

$ sudo grep -Po '^([ \t]*(menuentry|submenu) (.).+?\3)' /boot/grub/grub.cfg
[sudo] password for hannu:           
    menuentry 'Revert system only'
    menuentry 'Revert system and user data'
    menuentry 'Revert system only (recovery mode)'
    menuentry 'Revert system and user data (recovery mode)'
menuentry 'Ubuntu 24.04 LTS'
submenu 'Advanced options for Ubuntu 24.04 LTS'
    menuentry 'Ubuntu 24.04 LTS, with Linux 6.8.0-31-generic'
    menuentry 'Ubuntu 24.04 LTS, with Linux 6.8.0-31-generic (recovery mode)'
menuentry "Memory test (memtest86+x64.efi)"
menuentry 'Memory test (memtest86+x64.efi, serial console)'
        menuentry 'UEFI Firmware Settings'

$ 

Answer 5

When I have initially posted this I haven't noticed the OP's specific requirement not to propose grub-customizer... Sorry.

For what it's worth I'll leave it here but also confirm that the best solution is indeed the most up-voted one HERE, with variables that can be found as indicated in THIS complementary answer.

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In order to do it with a GUI, I use Grub Customizer (I'm in Mint but that doesn't count here).

The simplest and most direct way (thanks @eMKi for the suggestion in comment) — best suited for a permanent setting, in General Settings > default entry > predifined, simply select the desired kernel in the drop-down list.

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Or, in case one needs the "previous booted entry" to be the one selected (might be useful in dual boot with Windows when doing an Windows update that requires restart, for example) — keeping the Advanced options in the grub list in case the default list is changed within Grub Customizer:

under General settings select the default entry: previous booted entry.

Then, reboot, and during boot select the "Advanced options" entry in the grub list:

and select the older kernel

On the next reboot, the "Advanced options" item will be the one selected by default in the grub list and the last selected kernel from under there will be booted (without opening the full list of kernels).

In case Windows is used, or other option in the grub list, remember to re-do the previous procedure.

Answer 6

In order to change the default kernel to load you can set kernel boot priority in /etc/default/grub file.

First Take a backup of /etc/default/grub before making any changes.

While booting if you don't see Grub boot loader at all, you have to make it visible, for that change these 2 lines in Grub as

GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10

Now while loading you should be able to see the grub menu.

To change the kernel loading priority you have to make a change in GRUB_DEFAULT as the default setting it is set as

GRUB_DEFAULT=0

check the serial number of the kernel that you want to set as default, the numbering is 0 indexed, change the index accordingly. eg if you want to load the 6th entry from the top, you have to set the index as 5.

GRUB_DEFAULT=5

Now update grub using sudo update-grub and restart.

Check this YouTube video to make grub visible.

Check this Ubuntu help page to know about GRUB_DEFAULT.

Answer 7

On Ubuntu 22.04, and possibly other distros & versions, you can configure grub to remember the last selected entry made at boot time, and use this as the default in subsequent boots.

To enable this, edit /etc/default/grub and add the following lines:

GRUB_SAVEDEFAULT=true
GRUB_DEFAULT=saved

Then run sudo update-grub to regenerate the boot files, and then reboot.

Now in grub, when you select a kernel, e.g. from the "Advanced options for Ubuntu" submenu, grub will automatically remember the selection for the next time, and then boot the selected kernel.

This selection is stored in /boot/grub/grubenv, and it should not be edited directly. If you need to modify it from a booted system, you can use sudo grub-editenv:

$ sudo grub-editenv list
saved_entry=gnulinux-advanced-20795ce5-2ede-4ea5-994d-c665c5037760>gnulinux-5.15.0-76-generic-advanced-20795ce5-2ede-4ea5-994d-c665c5037760

$ sudo grub-editenv set 'saved_entry=...'

The entry names can be copy/pasted from /boot/grub/grub.cfg, and note in particular the submenu's menuentry_od_option, followed by >, followed by the menuentry_id_option value of the selected item. Use quotes around the set string to prevent the shell seeing > as a redirect.

For example, this:

submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-20795ce5-2ede-4ea5-994d-c665c5037760' {
    menuentry 'Ubuntu, with Linux 5.19.0-46-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.19.0-46-generic-advanced-20795ce5-2ede-4ea5-994d-c665c5037760' {
        ...

Would result in the command:

$ sudo grub-editenv set 'saved_entry=gnulinux-advanced-20795ce5-2ede-4ea5-994d-c665c5037760>gnulinux-5.19.0-46-generic-advanced-20795ce5-2ede-4ea5-994d-c665c5037760'

The net effect of this feature is that grub, if left to boot automatically, will always pick the last selected boot option, which is a kind of default behaviour. Just be aware that temporarily selecting another kernel will change the default, but you can disable this by removing GRUB_SAVEDEFAULT from /etc/default/grub and regenerating the grub files with sudo update-grub, once you have your default kernel saved.

Answer 8

To load with a specific kernel, follow the below steps,

1. Check the available kernel by using the below command;

sudo grep menuentry /boot/grub/grub.cfg

From the list first kernel number starts from 0, and so on

2. Edit GRUB configuration file

sudo vi /etc/default/grub

If you want to go with 5th kernel, then mention the GRUB_DEFAULT below

GRUB_DEFAULT='1>4'

save the file and exit the text editor

3. update GRUB

sudo update-grub

4. Reboot the Server, and to check the kernel version, use the below command;

uname -r