The default kernel in Ubuntu 18.04 LTS Amazon Machine Image (AMI) is a linux-aws 4.15 based kernel, but now Canonical has switched it to a rolling kernel model.
Canonical has followed the rolling kernel model in its other cloud environments for some time now, and found it's an excellent way to deliver enhancements and still provides LTS level stability.
The rolling kernel model is available in the latest interim Ubuntu release, and has also been applied to 18.04, but the linux-aws kernel is still a 4.15 based kernel and when roll, it becomes a 5.3 based kernel. And the model transitions the default linux-aws kernel from one base version to the other as part of regular patching cycle.
What is the Rolling Kernel Model?
The default linux-aws kernel is transitioned from one base version to the next as part of its regular patching cycle through a model known as rolling kernel.
Applying this model to 18.04, with the linux-aws kernel still a 4.15 based kernel, when roll, it will become a 5.3 based kernel which was part of 19.10 interim release. And that 5.3 kernel is now available for preview as the linux-aws-edge kernel.
It's important to bear in mind that both the linux-aws-edge kernels and the rolling release kernels are fully baked prior to being made available for use and they meet the same quality and durability standards all kernels must meet before release.
How Ubuntu users can Prepare for the ‘roll’?
For installation of the 5.3 linux-aws-edge kernel, which is now available for testing, you need to follow the instructions for using a terminal window as detailed below.
Kindly note that this instance is running the standard linux-aws kernel (v4.15.0):
ubuntu@ip-xxx-xxx-xxx-xxx$ uname -r 4.15.0-xxxx-aws
Then 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
If you are prompted about a new version of /boot/grub/menu.lst, simply select the default: “keep the local version currently installed”.
However, if you don't want to roll to new kernel but rather to stay on the 4.15 based kernel, which support continues for the length of the LTS, simply type the below 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
For now, if you roll your kernel, you’ll shift to 5.3 kernel which is now available for preview as the linux-aws-edge kernel. Hence, it is recommended that users run with their workloads in non-production deployments. And if you did give it a spin, you can provide feedback on the Filing Ubuntu Kernel Bugs wiki.