Switch from real-time to generic kernel

Switching from the real-time kernel back to the generic kernel requires manual configuration. This guide describes how to disable the real-time kernel Pro service and restore the system to a generic kernel configuration. It applies to both GRUB-based systems and Raspberry Pi devices running Ubuntu Server or Ubuntu Desktop.

For switching between kernel versions on Ubuntu Core, refer to this document.

Check if other kernels are installed

Before removing the real-time kernel, check whether other kernel versions are already installed.

Note

Raspberry Pi kernel packages use the -raspi suffix instead of -generic.

List the installed kernels:

GRUB systemRaspberry Pi

ubuntu@ubuntu:~$

apt list linux-generic* --installed

linux-generic-6.11/noble-updates,noble-security,now 6.11.0-29.29~24.04.1 amd64 [installed]
linux-generic-6.14/noble-updates,noble-security,now 6.14.0-24.24~24.04.3 amd64 [installed]
linux-generic-hwe-24.04/noble-updates,noble-security,now 6.14.0-24.24~24.04.3 amd64 [installed]

If non-real-time kernels are already installed, proceed to disable the real-time Pro service.

Otherwise, install a generic kernel first:

GRUB systemRaspberry Pi

For GRUB systems, search using apt for generic Linux kernels:

apt list linux-generic*

Install the required kernel package:

sudo apt install <package-name>

Disable the real-time service on Pro

Disable the realtime-kernel Pro service:

ubuntu@ubuntu:~$

sudo pro disable realtime-kernel

This will remove the boot order preference for the real-time kernel and
disable updates to the real-time kernel.

This will NOT fully remove the kernel from your system.

After this operation is complete you must:
  - Ensure a different kernel is installed and configured to boot
  - Reboot into that kernel
  - Fully remove the realtime kernel packages from your system
      - This might look something like `apt remove linux*realtime`,
        but you must ensure this is correct before running it.

Are you sure? (y/N) y
Removing APT access to Real-time kernel
Updating package lists

Check the kernel version using the uname -r command:

ubuntu@ubuntu:~$

uname -r

6.8.1-1024-realtime

If it ends with -realtime, it means the system still uses the real-time kernel. You must manually remove the real-time kernel package.

Remove the real-time kernel

Danger

Before proceeding, confirm that you have another kernel installed. The system will become unbootable if the real-time kernel is removed and no other kernels are present.

Remove real-time kernel packages:

sudo apt remove linux*realtime*

All packages matching the wildcard will be selected. Review the list and confirm.

A warning may appear during the removal. Select <No> to continue the removal.

Finally, reboot the system. It should start with the generic kernel.

Verify that by running uname -r:

ubuntu@ubuntu:~$

uname -r

6.14.0-24-generic