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Ubuntu: Install Kernel and Set GRUB Default Kernel

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
@dreamerboy0406
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dreamerboy0406 commented Nov 19, 2022

I have tried following this steps but update-grub isn't updating the grub file.
what am I missing?

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