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System Extensions

Customizing the Talos Linux immutable root file system.

System extensions allow extending the Talos root filesystem, which enables a variety of features, such as including custom container runtimes, loading additional firmware, etc.

System extensions are only activated during the installation or upgrade of Talos Linux. With system extensions installed, the Talos root filesystem is still immutable and read-only.

Installing System Extensions

Note: the way to install system extensions in the .machine.install section of the machine configuration is now deprecated.

Starting with Talos v1.5.0, Talos supports generation of boot media with system extensions included, this removes the need to rebuild the initramfs.xz on the machine itself during the installation or upgrade.

There are two kinds of boot assets that Talos can generate:

  • initial boot assets (ISO, PXE, etc.) that are used to boot the machine
  • disk images that have Talos pre-installed
  • installer container images that can be used to install or upgrade Talos on a machine (installation happens when booted from ISO or PXE)

Depending on the nature of the system extension (e.g. network device driver or containerd plugin), it may be necessary to include the extension in both initial boot assets and disk images/installer, or just the installer.

The process of generating boot assets with extensions included is described in the boot assets guide.

Example: Booting from an ISO

Let’s assume NVIDIA extension is required on a bare metal machine which is going to be booted from an ISO. As NVIDIA extension is not required for the initial boot and install step, it is sufficient to include the extension in the installer image only.

  1. Use a generic Talos ISO to boot the machine.
  2. Prepare a custom installer container image with NVIDIA extension included, push the image to a registry.
  3. Ensure that machine configuration field .machine.install.image points to the custom installer image.
  4. Boot the machine using the ISO, apply the machine configuration.
  5. Talos pulls a custom installer image from the registry (containing NVIDIA extension), installs Talos on the machine, and reboots.

When it’s time to upgrade Talos, generate a custom installer container for a new version of Talos, push it to a registry, and perform upgrade pointing to the custom installer image.

Example: Disk Image

Let’s assume NVIDIA extension is required on AWS VM.

  1. Prepare an AWS disk image with NVIDIA extension included.
  2. Upload the image to AWS, register it as an AMI.
  3. Use the AMI to launch a VM.
  4. Talos boots with NVIDIA extension included.

When it’s time to upgrade Talos, either repeat steps 1-4 to replace the VM with a new AMI, or like in the previous example, generate a custom installer and use it to upgrade Talos in-place.

Authoring System Extensions

A Talos system extension is a container image with the specific folder structure. System extensions can be built and managed using any tool that produces container images, e.g. docker build.

Sidero Labs maintains a repository of system extensions.

Resource Definitions

Use talosctl get extensions to get a list of system extensions:

$ talosctl get extensions
NODE         NAMESPACE   TYPE              ID                                              VERSION   NAME          VERSION   runtime     ExtensionStatus        1         gvisor        20220117.0-v1.0.0   runtime     ExtensionStatus   1         intel-ucode   microcode-20210608-v1.0.0

Use YAML or JSON format to see additional details about the extension:

$ talosctl -n get extensions -o yaml
    namespace: runtime
    version: 1
    owner: runtime.ExtensionStatusController
    phase: running
    created: 2022-02-10T18:25:04Z
    updated: 2022-02-10T18:25:04Z
        name: intel-ucode
        version: microcode-20210608-v1.0.0
        author: Spencer Smith
        description: |
            This system extension provides Intel microcode binaries.
                version: '>= v1.0.0'

Example: gVisor

See readme of the gVisor extension.