How to create your Red Hat Enterprise Linux 9 for ARM 64 image with MicroShift using Image Builder

Being involved in a demo of Red Hat Enterprise Linux for Edge, MicroShift and ImageBuilder and due to problems with the network driver in RHEL 8.x for Raspberry PI 4 the need arose to have a custom image in version 9 (where the Ethernet network driver does work, but not the wireless). Since there is no RHEL 9 AMI in the AWS marketplace (at the time of writing is a Beta version), I have documented the steps to be performed in my git repo: rhel9-arm-ami.

Assuming that all the work in the rhel9-arm-ami repo has been done (creation of the AMI), I have documented the steps to follow in order to build your RHEL 9 for Edge ARM 64 custom image (with MicroShift).

Building RHEL for Edge with Image Builder

Let's look at using Image Builder to create a RHEL 9 for Edge with MicroShift raw image.

Image Builder can create installer media that embeds the OSTree commit. This is perfect for disconnected environments that require an ISO, thumb drive, or some form of media that doesn't depend on network access. In our case, we are going to use the raw format.

Prerequisites

In order to perform all the steps as documented, we will need an AWS account and access to the EC2 Graviton service (ARM compute).

Of course, although the purpose is to show the whole process based on ARM architecture, depending on the computing capacity you have on your laptop or server, you can make use of KVM and virtualization and avoid all the Amazon stuff.

WARNING: As mentioned above, it is important to have all the work discussed in the rhel9-arm-ami repo. If not, the following steps are likely to vary and may not work correctly.

Launch the EC2 Graviton instance

We are going to launch a Graviton instance, which is what AWS calls EC2 instances with ARM architecture.

1. Create ssh key-pair (optional):

   ssh-keygen -b 4096

   NOTE: Optional. You can create new ones or use existing ones, necessary to be able to connect to the EC2 instance.

2. Import key:

   aws ec2 import-key-pair --key-name "image_builder" --public-key-material fileb://~/.ssh/image_builder.pub

3. Start the instance:

   aws ec2 run-instances \
       --image-id ami-0f890ee1070bb67cf \
       --instance-type t4g.medium \
       --subnet-id subnet-0f0b77ba349b21e50 \
       --security-group-ids sg-047e6a8ef2b4edb23 \
       --associate-public-ip-address \
       --key-name image_builder \
       --block-device-mappings "[{\"DeviceName\":\"/dev/xvda\",\"Ebs\":{\"VolumeSize\":60,\"DeleteOnTermination\":true}}]" \
       --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=image-builder}]'

   WARNING: image-id is the ID of the custom AMI I created (is not an existing or valid ID within the AWS public marketplace)

Install Image Builder

Step by step:

1. Register the system

   subscription-manager register --username your@user.com --password your_password
   subscription-manager role --set="Red Hat Enterprise Linux Server"
   subscription-manager service-level --set="Self-Support"
   subscription-manager usage --set="Development/Test"

2. Install Image Builder

   yum install -y osbuild-composer
   systemctl enable --now osbuild-composer.socket

3. Install composer

   yum install -y composer-cli

4. Enable web console

   yum install -y cockpit-composer
   systemctl enable --now cockpit.socket

5. Install conteainer tools

   yum module install -y container-tools

TIP: Step 4 and 5 are optional, but help to have a complete environment ready for any kind of scenario. The web console makes it easy to generate/download the image and the container tools make it possible to control the OSTree Commit container image via podman / skopeo.

MicroShift & Image Builder

We need to configure a repository override to be able to add custom repositories (or repositories that are different from the default repositories):

1. Create the directory

   mkdir -p /etc/osbuild-composer/repositories

2. Copy the file rhel-90.json to the directory

   cp utils/rhel-90.json /etc/osbuild-composer/repositories/

3. Add new repositories to the server

   composer-cli sources add utils/transmission.toml
   composer-cli sources add utils/microshift.toml

   INFO: A new source repository can be added by creating a TOML file with the details of the repository and add it to the server. We need to add the following repos to access the MicroShift packages:

   • transmission.toml
   • microshift.toml

4. Reboot Image Builder to detect the changes

   systemctl restart osbuild-composer.service

5. Build the image:

   composer-cli blueprints push utils/microshift-blueprint-v0.0.1.toml

   TIP: Within the supported customizations within the blueprint I would recommend adding at least the public ssh key. For more information see the documentation: Supported Image Customizations

Installing Images on Raspberry Pi

Once we have our image created, we can download it by using composer-cli or the cockpit web console and burn it into our Raspberry.

Here you have multiple choices:

• etcher
• Raspberry Pi Imager
• On Linux

Recommended links

As you have seen, this is a very specific scenario / use case, but if you want to go deeper into topics such as Edge, Image Builder and/or MicroShift, I recommend the following links:

• Building RHEL for Edge with Image Builder
• RHEL for Edge deployment types: from my buddy @luisarizmendi with very good scripts
• Introducing MicroShift: amazing post regarding MicroShift and its role in the Edge from my pal @oglok