Using hardware-enablement kernels

Note

This feature is available in MAAS versions 1.5 and above.

MAAS allows you to use hardware enablement kernels when booting nodes that require them.

What are hardware-enablement kernels?

Brand new hardware gets released all the time. We want that hardware to work well wih Ubuntu and MAAS, even if it was released after the latest release of MAAS or Ubuntu. Hardware Enablement (HWE) is all about keeping pace with the new hardware.

Ubuntu’s solution to this is to offer newer kernels for older releases. There are at least two kernels on offer for Ubuntu releases: the “generic” kernel – i.e. the kernel released with the current series – and the Hardware Enablement kernel, which is the most recent kernel release.

There are separate HWE kernels for each release of Ubuntu, referred to as hwe-<release letter>. So, the 14.04 / Trusty Tahr HWE kernel is called hwe-t, the 12.10 / Quantal Quetzal HWE kernel is called hwe-q and so on. This allows you to use newer kernels with older releases, for example running Precise with a Saucy (hwe-s) kernel.

For more information see the LTS Enablement Stack page on the Ubuntu wiki.

Importing hardware-enablement kernels

Hardware-enablement kernels need to be imported to a cluster controller before that cluster’s nodes can use them.

In order to import HWE kernels to a cluster controller you need to edit the controller’s /etc/maas/bootresources.yaml file, and update the subarches that you want to import, like this:

boot:
  storage: "/var/lib/maas/boot-resources/"

  sources:
    - path: "http://maas.ubuntu.com/images/ephemeral-v2/releases/"
      keyring: "/usr/share/keyrings/ubuntu-cloudimage-keyring.gpg"
      selections:
        - release: "precise"
          arches: ["i386", "amd64"]
          subarches: ["generic", "hwe-q", "hwe-r", "hwe-s", "hwe-t"]
          labels: ["release"]

Once you’ve updated bootresources.yaml, you can tell the cluster to re-import its boot images using the maas command (You will need to be logged in to the API first):

$ maas <profile-name> node-group import-boot-images \
  <cluster-controller-uuid>

You can also tell the cluster controller to re-import its boot images by clicking the Import boot images button in the Clusters page of the MAAS web UI.

Using hardware-enablement kernels in MAAS

A MAAS administrator can choose to use HWE kernels on a per-node basis in MAAS.

The quickest way to do this is using the MAAS command, like this:

$ maas <profile-name> node update <system-id>
  architecture=amd64/hwe-t

If you specify an architecture that doesn’t exist (e.g. amd64/hwe-z), the maas command will return an error.

It’s also possible to use HWE kernels from the MAAS web UI, by visiting the Node’s page and clicking Edit node. Under the Architecture field, you will be able to select any HWE kernels that have been imported onto that node’s cluster controller.