OS Image

Describes the OS images used to create Kubernetes nodes using the byo provider.

You need the following to perform a BYO installation:

An Oracle Linux kernel to boot.
An initrd (initial ramdisk) that matches the boot kernel.
A root file system that can run Anaconda and Kickstart.
A method to perform an automated installation using Kickstart.
A method to serve the OCK OSTree archive.
A method to serve Ignition files.

An easy way to achieve the first four points is to download an Oracle Linux ISO file. For information about the available ISO files, see Oracle Linux ISO Images.

A Kickstart file defines an automated installation using a local OSTree archive server. For information on creating a Kickstart file, see Oracle Linux 9: Installing Oracle Linux or Oracle Linux 8: Installing Oracle Linux.

The CLI can generate a container image that serves an OSTree archive over HTTP. The container image can be served using a container runtime such as Podman, or inside a Kubernetes cluster. You can also generate an OSTree archive manually and serve it over any HTTP server.

Ignition files can be served using any of the platforms listed in the upstream Ignition documentation. You could also embed the Ignition configuration file directly on to the root file system of the host if the installation is done reasonably close to when the Ignition configuration was generated.

Figure 8-2 OCK Images in a Bring Your Own Cluster

This image shows the creation of an OCK image for a BYO cluster. An Oracle Linux ISO provides the host OS components, with an OSTree image (based on the OCK image in the container registry). The resulting OSTree image is loaded into a container registry, or other method to serve a container. An ignition file is generated by the CLI and is served by an Ignition server. A Kickstart file must be created to include the location of the Ignition file and the OSTree image and made available on a Kickstart server.

CLI: The CLI used to create and manage Kubernetes clusters. The ocne command.
Default configuration: A YAML file that contains configuration for all ocne commands.
Cluster configuration: A YAML file that contains configuration for a specific Kubernetes cluster.
Container registry: A container registry used to pull the OCK OSTree images. The default is the Oracle Container Registry.
OCK OSTree Image: The OCK OSTree image pulled from the container registry.
Ephemeral cluster: A temporary Kubernetes cluster used to perform a CLI command.
Container registry/Podman: A container registry or container server, such as Podman, used to serve the OCK OSTree images.
Oracle Linux ISO: An ISO file to serve the kernel and initrd to use for the OS on nodes.
Ignition file: An Ignition file, generated by the CLI, used to join nodes to a cluster.
Ignition server: The Ignition file, loaded into a method that serves Ignition files.
Kickstart file: A Kickstart file that provides the location of the OCK OSTree image, Ignition file, and the OS kernel and initrd.
Kickstart server: The Kickstart file, loaded into a method that servers Kickstart files.

Oracle Linux ISO Images

Describes the Oracle Linux ISO image used for OS images with the byo provider.

You can use any of the available Oracle Linux ISO images as the basis for the OS image. Only the kernel, initrd, and root file system from the media is used. All installation content comes from the OCK OSTree archive. The ISO images are available on the Oracle Linux yum server.

We recommend you use a UEK boot ISO file as these are smaller and include all the OS components required.

OSTree Archive Server

Describes the OSTree archive used for building an OS image with the byo provider.

A container image that contains the OSTree archive can be generated using the ocne image create command. For example:

ocne image create --type ostree

A Kubernetes cluster is used to download and generate the OSTree archive image. Any running cluster can be used. To specify which cluster to use, set the KUBECONFIG environment variable, or use the --kubeconfig option of ocne commands. If no cluster is available, a cluster is created automatically using the libvirt provider, with the default configuration.

The image might take some time to download and generate. When completed, the image is available in the $HOME/.ocne/images/ directory.

Use the ocne image upload command to upload the image to a location where it can be used. Container images can be uploaded using any transport provided by libcontainer. See containers-transports(5) for the list of transports. A transport is always required.

Typically, the image is uploaded to a container registry. For example:

ocne image upload --type ostree --file $HOME/.ocne/images/ock-1.31-amd64-ostree.tar --destination docker://myregistry.example.com/ock-ostree:latest --arch amd64

To load the container image into the local image cache, use the Open Container Initiative image loading facility built in to a container runtime or other some other tool that performs the same task. For example, to load the image into Podman:

podman load < $HOME/.ocne/images/ock-1.31-arm64-ostree.tar

Creating an OSTree Image for the Bring Your Own Provider

Create an OSTree image for the Bring Your Own (byo) provider. Then upload the image to a container registry so it can be used as the boot disk for Virtual Machines (VMs).

You can load the image into several destinations. This example show you how to load the image into a container registry. For information on setting up a container registry, see Oracle Linux: Podman User's Guide.

You can load the image into any target available with the Open Container Initiative transports and formats. See containers-transports(5) for available options.

(Optional) Set the location of the kubeconfig file for an existing cluster.

A Kubernetes cluster is required to perform some steps. You can use an existing cluster for this purpose by setting the location of the kubeconfig file.

You can set this using the KUBECONFIG environment variable, or using the --kubeconfig option with ocne commands. You could also set this in a configuration file.

If you don't set the location of the kubeconfig file, an ephemeral cluster is created using the libvirt provider when required.
(Optional) Set up the libvirt provider.

If you don't set the location of an existing Kubernetes cluster, set up the localhost to provision ephemeral clusters using the libvirt provider. For information on setting up the libvirt provider, see Setting Up the libvirt Provider.
Create an OSTree image.
Use the ocne image create command to create a OSTree image. The syntax is:
```
ocne image create 
{-a|--arch} arch
[{-t|--type} provider]
[{-v|--version} version]
```
For more information on the syntax options, see Oracle Cloud Native Environment: CLI.

For example:
```
ocne image create --type ostree --arch arm64 
```
This command might take some time to complete.

The Kubernetes cluster generates the OSTree image, and the image is saved to the $HOME/.ocne/images/ directory.
Upload the OSTree image to a container registry.
Use the ocne image upload command to upload the image to a container registry. The syntax is:
```
ocne image upload 
{-a|--arch} arch
[{-b|--bucket} name]
{-c|--compartment} name
[{-d|--destination} path]
{-f|--file} path
{-i|--image-name} name 
{-t|--type} provider
{-v|--version} version
```
For more information on the syntax options, see Oracle Cloud Native Environment: CLI.

For example:
```
ocne image upload --type ostree --file $HOME/.ocne/images/ock-1.31-amd64-ostree.tar --destination docker://myregistry.example.com/ock-ostree:latest --arch amd64
```
The Kubernetes cluster uploads the OSTree image. A sign in prompt is provided if credentials aren't set for the target container registry. The image is uploaded to the container registry. The image can now be used to create VMs to use in a Kubernetes cluster.