Linux - set next boot kernel [duplicate]

Solution 1:

Display Grub Menu Entries from Command Line

I created a script grub-menu.sh to make it easy to find the menu entry number:

Booting with Grub Menu Entry Number

If you wanted to reboot into Kernel 4.4.0-131 you would use:

sudo grub-reboot "1>6"

Getting the bash script grub-menu.sh

You can find the bash script in this Q&A: Display grub menu and options without rebooting?

Solution 2:

It seems the kernel you want to boot is in a submenu of grub (just look at the complete grub.cfg). man grub-reboot says:

Please note that menu items in submenus or sub-submenus require specifying the submenu components and then the menu item component. The titles should be separated using the greater-than character (>) with no extra spaces. Depending on your shell some characters including > may need escaping. More information about this is available in the GRUB Manual in the section about the 'default' command.

Maybe something like grub-reboot '2>2' will work for you.

Solution 3:

I've been in a similar situation, and wanted a simple way to reboot into a different kernel or set the default. The menus that are generated in Ubuntu do make this less than trivial.

I've put together a script called boot-kernel that makes this easier. Its not perfect, but works well for at least official ubuntu kernels.

$ sudo ./boot-kernel --setup-only
changing GRUB_DEFAULT from 0 to "saved" in /etc/default/grub
apply change to /etc/default/grub
   --- /etc/default/grub    2018-01-12 19:40:38.681080878 +0000
   +++ /tmp/boot-kernel.GXbsRC  2018-01-12 19:40:50.525044373 +0000
   @@ -3,7 +3,7 @@
    # For full documentation of the options in this file, see:
    #   info -f grub -n 'Simple configuration'

   -GRUB_DEFAULT=0
   +GRUB_DEFAULT=saved
    GRUB_HIDDEN_TIMEOUT=0
    GRUB_HIDDEN_TIMEOUT_QUIET=true
    GRUB_TIMEOUT=0
execute: update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.4.0-109-generic
Found initrd image: /boot/initrd.img-4.4.0-109-generic
Found linux image: /boot/vmlinuz-4.4.0-108-generic
Found initrd image: /boot/initrd.img-4.4.0-108-generic
done

$ sudo ./boot-kernel /boot/vmlinuz-4.4.0-108-generic
GRUB_DEFAULT already set to 'saved'. no change necessary.
selected /boot/vmlinuz-4.4.0-108-generic. entry: Advanced options for Ubuntu>Ubuntu, with Linux 4.4.0-108-generic
execute: grub-reboot "Advanced options for Ubuntu>Ubuntu, with Linux 4.4.0-108-generic"