Select Specific Kernel Version for Deploy

Users
1

I feel like this should be super easy. How do i specify the kernel version for a machines deployment? I have an issue where the new kernel version is not supported for one of my solutions and i need to ensure that the older kernel version is deployed.

For example:

Deployed: 6.8.0-59-generic
Needed: 6.8.0-58-generic

2

Hey there :slight_smile:

Nope, that’s unfortunately not super easy :sweat_smile: you have 2 options:

  1. (not super easy, but definitely ideal) you create your own simplestream server and you put there the kernel you want for your image
  2. (hacky solution - please do some tests a dev environment as I did not test it) say you want to replace the kernel for the noble image, then go to Index of /ephemeral-v3/stable/noble/amd64/20250424/ga-24.04/generic (currently the latest image available, it might change in the future as it is updated regularly) and download it. Then run sha256sum boot-kernel and run the following query on the DB
select filename_on_disk from maasserver_bootresourcefile where sha256='<THE SHA YOU COMPUTED ABOVE>';

then finally mv boot-kernel /var/snap/maas/common/maas/image-storage/<THE FILENAME_ON_DISK YOU EXTRACTED ABOVE>.

Also, note that as a new image is pushed to the upstream server your kernel might be removed/replaced. So you either

  1. disable the automatic refresh of the images
  2. use the solution 1 - your own simplestream server
  3. you do this process again

Please let me know if this works

3

We use curtin to config, from this document Custom machine setup , you can edit your own curtin config for one distro.

just like we use 5.4.0-131-generic for 18.04; so we add a file name with curtin_userdata_ubuntu_amd64_generic_bionic in path /etc/maas/preseeds/ and with config like

kernel:
  package: "linux-image-5.4.0-131-generic"
  fallback-package: "linux-image-generic-hwe-18.04"

late_commands:
... 
  25-install-modules: ["curtin", "in-target", "--", "bash", "-c", ":; KVER=$(ls -t /boot/vmlinuz-* | head -n 1 | sed 's/.*vmlinuz-//g'); apt-get -y install linux-modules-${KVER} linux-modules-extra-${KVER} linux-headers-${KVER}"]
...

......

You need fallback-package config because sometimes they may delete some kernel, and you will deployed failed. And remember install extra-modules package.