Introducing the Ubuntu AWS Rolling Kernel

The linux-aws 4.15 based kernel, which is the default kernel in the Ubuntu 18.04 LTS AMIs, is moving to a rolling kernel model.

Why is this changing?

The Ubuntu rolling kernel model provides the latest upstream bug fixes and performance improvements around task scheduling, I/O scheduling, networking, hypervisor guests and containers to our users. Canonical has been following this model in other cloud environments for some time now, and have found it to be an excellent way to deliver these benefits while continuing to provide LTS level stability.

What is the rolling kernel model?

A rolling kernel model transitions the default linux-aws kernel from one base version to the next as part of its regular patching cycle. That new kernel is the kernel of the latest interim Ubuntu release.  Applying this model directly to 18.04 today, the linux-aws kernel is a 4.15 based kernel and when we roll, it will become a 5.3 based kernel which was part of our 19.10 interim release.  

Today, that 5.3 kernel is currently available for preview as the linux-aws-edge kernel, which we encourage all users to run with their workloads in non-production deployments.  It is important to keep in mind that both the -edge kernels and the rolling release kernels are fully baked prior to being made available for our customers to use and meet exactly the same quality and durability standards all our kernels must meet for release. 

When the linux-aws kernel rolls forward, a user would see this change in 1 of 2 ways, 1) launching the latest AMI would have the newer kernel, and 2) users applying packaging updates, or via automatic security updates, will also see the newer kernel.

How do I prepare for the ‘roll’?

To install the 5.3 linux-aws-edge kernel, which is currently available for customer testing today, please follow these short instructions using a terminal window:

Note that the instance is running the standard linux-aws kernel (v4.15.0):

ubuntu@ip-xxx-xxx-xxx-xxx$ uname -r
4.15.0-xxxx-aws

Install the linux-aws-edge kernel and reboot the instance:

ubuntu@ip-xxx-xxx-xxx-xxx$ sudo apt update
ubuntu@ip-xxx-xxx-xxx-xxx$ sudo apt install -y linux-aws-edge

Note: If prompted about a new version of /boot/grub/menu.lst, select the default choice: “keep the local version currently installed”.

ubuntu@ip-xxx-xxx-xxx-xxx$ sudo reboot

Confirm that the instance is now running the linux-aws-edge kernel (v5.3.0):

ubuntu@ip-xxx-xxx-xxx-xxx$ uname -r
5.3.0-xxxx-aws

What if I don’t want my kernel to roll?

If you do not want to roll to a new kernel but instead stay on the 4.15 based kernel (which will continue to get full support and updates for the length of the LTS), just type the following instructions into a terminal window ssh’d into your instance:

ubuntu@ip-xxx-xxx-xxx-xxx$ sudo apt update
ubuntu@ip-xxx-xxx-xxx-xxx$ sudo apt install linux-aws-lts-18.04

How can you provide feedback?

The best way to provide feedback on Ubuntu products is to file a bug.   Filing Ubuntu Kernel Bugs