Kernel Management

Node Kernels

Warewulf nodes require a Linux kernel to boot. There are multiple ways to do this, but the default and easiest way is to install the kernel you wish to use for a particular container into the container.

Warewulf will locate the kernel automatically within the container and by default use that kernel for any node configured to use that container image.

You can see what kernel is included in a container by using the wwctl container list command:

# wwctl container list
  alpine          0                                     05 Jun 23 20:02 MDT  05 Jun 23 20:02 MDT  17.9 MiB
  rocky-8         1      4.18.0-372.13.1.el8_6.x86_64   17 Jan 23 23:48 MST  06 Apr 23 09:40 MDT  2.4 GiB

Here you will notice the alpine contianer that was imported has no kernel within it, and the rocky container includes a kernel.

This model was introduced in Warewulf v4.3. Previously, Warewulf managed the kernel and the container separately, which made it hard to build and distribute containers that have custom drivers and/or configurations included (e.g. OFED, GPUs, etc.).

Kernel Overrides

It is still possible to specify a kernel for a container if it doesn’t include it’s own kernel, or if you wish to override the default kernel by using the kernel override capability.

You can specify this option with the --kerneloverride option to wwctl node set or wwctl profile set commands.

In this case you will also need to import a kernel specifically into Warewulf for this purpose using the wwctl kernel import command as follows:

# wwctl kernel import $(uname -r)
4.18.0-305.3.1.el8_4.x86_64: Done

This process will import not only the kernel image itself, but also all of the kernel modules and firmware associated with this kernel.

Listing All Imported Kernels

Once the kernel has been imported, you can list them all with the following command:

# wwctl kernel list
VNFS NAME                           NODES
4.18.0-305.3.1.el8_4.x86_64             0

# wwctl kernel list
KERNEL NAME                              KERNEL VERSION            NODES
4.18.0-305.3.1.el8_4.x86_64                                             0

Once a kernel has been imported you can configure it to boot compute nodes.