Workshop Exercise 2.3 - Converting Our Image Definition to Code

Table of Contents

• Objective
• Step 1 - Reviewing the infra.osbuild Collection
• Step 2 - Converting Our Image Definition to Code
• Step 3 - Customizations for Installing the Realtime Kernel
• Solutions

Objective

In this exercise, we are going to review the infra.osbuild collection and convert our WebUI configured image over to something we can use in an automated process.

This exercise will cover:

• The infra.osbuild collection
• How to convert our image definition to code

Step 1 - Reviewing the infra.osbuild Collection

At a high level, the infra.osbuild collection allows us to use Ansible to automate the previous exercise. We treat Image Builder as a “service” as sorts, simply feeding in our image definition and getting our composed image on the other end.

Because we’re converting our image definition over to code, we can apply some best practices (such as proper CI) to ensure our edge images are thoroughly tested before being rolled out to devices.

Step 2 - Converting Our Image Definition to Code

Instead of leveraging the Image Builder WebUI to build our image, we’ll instead leverage the infra.osbuild collection and the variables it expects to define our image, then have Ansible handle building the image.

Let’s start with an empty set of variables and walk through them:

builder_blueprint_name:
compose_type:
builder_compose_pkgs:
builder_compose_customizations:

First: builder-blueprint-name is the name of the blueprint we want to create. This time, let’s call ours student$(your-student-number)-blueprint-ansible, for example:

builder_blueprint_name: student1-blueprint-ansible

Next is compose_type, which we’ll set to edge-commit:

compose_type: edge-commit

After that, builder_compose_pkgs expects a list of packages to add to the image. We’ll add podman and vim-enhanced, and also a new package to help us manage wifi network connectivity:

builder_compose_pkgs:
  - podman
  - vim-enhanced
  - NetworkManager-wifi

Finally, we can specify our final customizations under the builder_compose_customizations dictionary:

builder_compose_customizations:
  user:
    name: ansible
    password: "$(password-from-your-student-page)"
    groups:
      - users
      - wheel

In this image, let’s leave the hostname unconfigured, and instead set it after the fact with Ansible later. In addition, we’ve added Ansible to the wheel group so it has administrative access on the system.

Take these customizations and create a file at playbooks/files/image-definition.yml with these variables. Be sure to save/commit your changes to your git repo.

Note:

It is absolutely not a good idea to commit passwords or secrets to a code repository. Don’t do this in production.

Step 3 - Customizations for Installing the Realtime Kernel

There are two main customizations for installing the realtime kernel: enabling the correct repository that contains the correct kernel, and specifying a customization to use that kernel over the default.

The infra.osbuild collection supports both of these modifications by defining variables, same as above.

First, to enable the correct repository:

builder_rhsm_repos:
  - rhel-9-for-x86_64-rt-rpms

And next, to install the realtime kernel:

builder_compose_customizations:
  kernel:
    name: kernel-rt

These simply need to be combined with our existing image definition to reach our desired state. Check out the Solutions below for the full yaml.

Again, remember to add these modifications to playbooks/files/image-definition.yml, and push the changes to your code repository.

Solutions

A fully populated playbooks/files/image-definition.yml:

---
builder_blueprint_name: student1-blueprint-ansible
compose_type: edge-commit
builder_compose_pkgs:
  - podman
  - vim-enhanced
  - NetworkManager-wifi
builder_compose_customizations:
  user:
    name: ansible
    password: "$(password-from-your-student-page)"
    groups:
      - users
      - wheel
  kernel:
    name: kernel-rt
builder_rhsm_repos:
  - rhel-9-for-x86_64-rt-rpms

---

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