Ubuntu: Install Kernel and Set GRUB Default Kernel

ubuntu_update_booting_kernel.md

Ubuntu: Install Kernel and Set GRUB Default Kernel

Install Kernel

Install the default kernel:

sudo apt install linux-generic

Set GRUB Default Kernel

1. Find entrance from /boot/grub/grub.cfg
   • Get the $menuentry_id_option:

     grep submenu /boot/grub/grub.cfg

     Example output:

     submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf' {

     'gnulinux-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf' is what we need.
   • Get the specific kernel option:

     grep gnulinux-4.15.0 /boot/grub/grub.cfg

     Example output:

     menuentry 'Ubuntu, with Linux 4.15.0-126-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-4.15.0-126-generic-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf' {

     'gnulinux-4.15.0-126-generic-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf' is what we need.
2. Set GRUB_DEFAULT in /etc/default/grub
   • Join two entry strings obtained above by '>', set to GRUB_DEFAULT.

     GRUB_DEFAULT='gnulinux-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf>gnulinux-4.15.0-126-generic-advanced-4591a659-55e2-4bec-8dbe-d98bd9e489cf'

3. Update grub

   sudo update-grub

4. Reboot the machine

Doesn't seem to work here, doesn't matter how I try it ... My ids look like:

gnulinux-6.2.0-20-generic-advanced-7ceb1b1a-7139-409e-aff6-4e6ea53ce07b

and

gnulinux-5.17.5-051705-generic-recovery-7ceb1b1a-7139-409e-aff6-4e6ea53ce07b

The automatic option it creates is always for the first one, while I want the deafult to be 5.17.5...

Worked for me thanks 👍

thanks for the script @boypt

Came here looking for the exact same thing, kernel 6.5 seems to be having problems with nvida gpu (390).
I made a function (put it in your .bash_aliases file or create a .bash_functions that you source at login)

kernel-default () {
 local _action=$1
 local _kernelver=$2
 if [[ ! "${_action}" =~ ^(set)$ || ! "${_kernelver}" ]] && [[ ! "${_action}" =~ ^(unset)$ ]]; then
    echo -e "\n\e[90m kernel-default <set|unset> (default list)\e[m"
     echo -e "\e[91m\n  No \e[4maction\e[;91m or \e[4;91mkernel\e[;91m ver defined, issue \e[mkernel-default set \$(uname -r)\e[91m as example,"
     echo -e "  or use any of the following existing:\e[m $(kernel-mgmt | awk -F "[-]" '/image/ {print $3 "-" $4}' | sed '$!N;s/\n/, /g')"
     echo -e "\n\e[94m    Example:\e[m kernel-default set $(uname -r | cut -d '-' -f1-2)\e[m\n"

     local _savedcustom=$(grub-editenv list | cut -d '>' -f2)
     if [ "${_savedcustom}" ]; then
         echo -e "\e[90m Default kernel override active: \e[m${_savedcustom}\n"
     else
         echo -e "\e[90m Default kernel override active: \e[mnone\n"
     fi
 elif [ "${_action}" == "set" ]; then
    local _mid=$(awk '/Advanced options for Ubuntu/{print $(NF-1)}' /boot/grub/grub.cfg | cut -d\' -f2)
    local _kid=$(awk "/with Linux $_kernelver/"'{print $(NF-1)}' /boot/grub/grub.cfg | cut -d\' -f2 | head -n1)
    echo -e "GRUB_DEFAULT=saved\nGRUB_SAVEDEFAULT=true" | sudo tee /etc/grub.d/95-savedef.cfg
    sudo chmod +x /etc/grub.d/95-savedef.cfg
    sudo grub-editenv /boot/grub/grubenv set saved_entry="${_mid}>${_kid}"
    sudo update-grub
 elif [ "${_action}" == "unset" ]; then
    sudo grub-editenv /boot/grub/grubenv unset saved_entry
    sudo rm -f /etc/grub.d/95-savedef.cfg
    sudo update-grub
 fi
}

you can use this to get the specific kernel you need, assuming is currently in use:

grep gnulinux-$(uname -r) /boot/grub/grub.cfg