What is the difference between realtime-kernel and livepatch in Ubuntu Advantage (Pro)?

Krzysztof J. Obara

1/31/24, 5:57 PM

I wanted to test Ubuntu Advantage/Pro options on my system:

~$ ▶ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 22.04.1 LTS
Release:    22.04
Codename:   jammy
~$ ▶ sudo pro status
SERVICE          ENTITLED  STATUS    DESCRIPTION
esm-apps         yes       enabled   Expanded Security Maintenance for Applications
esm-infra        yes       enabled   Expanded Security Maintenance for Infrastructure
livepatch        yes       enabled   Canonical Livepatch service
realtime-kernel  yes       disabled  Ubuntu kernel with PREEMPT_RT patches integrated

Enable services with: pro enable <service>

     Account: xyz@zyx.com
Subscription: Ubuntu Pro - free personal subscription
~$ ▶ sudo pro enable realtime-kernel
One moment, checking your subscription first
Real-time kernel cannot be enabled with Livepatch.
Disable Livepatch and proceed to enable Real-time kernel? (y/N)
Cannot enable Real-time kernel when Livepatch is enabled.

It seems that the two option livepatch and realtime-kernel are mutually exclusive. What is realtime-kernel option anyway? It's not mentioned in the manual: https://manpages.ubuntu.com/manpages/focal/man1/ua.1.html So how do these two options differ then? Is there an advantage to using either?

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Pilot6

1/31/24, 6:03 PM

These are completely two different things.

realtime-kernel is a kernel with low latency patches.

livepatch is a service that allows to patch a kernel without system reboot.

Real-time kernels are used in cases when latency is critical, e.g. in processing audio. https://ubuntu.com/blog/real-time-ubuntu-is-now-generally-available

Livepatch service is used for servers to avoid rebooting. https://ubuntu.com/security/livepatch

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