How to install the real-time kernel on Ubuntu Core

The Linux kernel on Ubuntu Core is a snap. Because of that, switching to another compatible kernel is fairly straightforward.

This guide assumes you have booted into Ubuntu Core, using one of the pre-built images published by Canonical. If you intend to build an image that includes a real-time kernel, refer to How to create a Real-time Ubuntu Core image instead.

Find available kernels

Run the following command on the same Ubuntu Core host, or on another system with the same architecture:

snap info pc-kernel

Tip

For the list of kernel snaps for other architectures, refer to the pc-kernel Snap Store page.

Under channels, look for entries that contain <version>-rt as prefix. Each channel consists of a track followed by the risk level. In general, look at the stable risk level to find the most reliable revisions.

Filter results with grep. For example, here are the stable real-time kernels compatible with Ubuntu Core 24:

ubuntu@machine-amd64:~$

snap info pc-kernel | grep 24-rt | grep stable

  24-rt-hwe-edge/stable:    6.14.0-1003.3~24.04.3       2025-06-17 (2558) 370MB -
  24-rt-hwe/stable:         6.11.0-1011.11~24.04.1      2025-06-26 (2551) 363MB -
  24-rt/stable:             6.8.1-1023.24               2025-06-19 (2550) 351MB -

Each row shows a snap channel, version, date, revision, and size. In reverse order:

• 24-rt/stable channel contains the real-time kernel for Ubuntu 24.04 LTS. The release is stable. The snap version 6.8.1-1023.24 indicates that the kernel version is 6.8.1.

• 24-rt-hwe/stable contains the real-time Hardware Enablement (HWE) kernel for Ubuntu 24.04 LTS. The kernel version is 6.11.0.

• 24-rt-hwe-edge/stable provides the most recent kernel version. The -edge suffix in the track indicates that this is an edge kernel published for early access to the 6.14 kernel.

See also

Read more about the Ubuntu kernel lifecycle and HWE kernels.

Switch to another kernel

Once you identify a suitable channel, switch to that channel and refresh the snap.

For example:

ubuntu@machine-amd64:~$

sudo snap refresh pc-kernel --channel=25.04-rt/stable

...

Broadcast message from root@uc-rt (Wed 2025-06-25 12:00:39 UTC):

reboot scheduled to update the system
The system will reboot now!

After the installation, the system will reboot automatically and boot with the new kernel:

ubuntu@machine-amd64:~$

uname -a

Linux uc-rt 6.14.0-1004-realtime #4-Ubuntu SMP PREEMPT_RT Fri May 23 22:22:42 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Tip

Install and run a benchmarking tool such as rt-tests to measure the system performance:

sudo snap install rt-tests --candidate
sudo cyclictest --mlockall --smp --priority=80 --interval=200 --distance=0 --loops=100000

Refer to Tools for measuring real-time metrics for more.