Author: Brandon B. Jozsa

"I would not give a fig for the simplicity this side of complexity, but I would give my life for the simplicity on the other side of complexity."
- Oliver Wendall Holmes Jr.

So you've read the post where I talking about ZTP for OpenShift Alpha Clusters, but you may have been thinking "I didn't see any ZTP manifests in that post". This is what we're going to cover in today's article, of course with a demonstration, and discuss why this could be beneficial.

Part I: Introduction

Most of the how required to generate an ISO from an install-config.yaml and agent.yaml were already discussed in the previous blog post, but I want to discuss some other considerations for generating installation media using openshift-install agent commands.

Part II: Parts of the Deployment

You may already be familiar with what Zero-Touch Provisioning is, and how Red Hat is leading this concept of git-instantiated bare metal deployments. But if you're unfamiliar with it, have a look at a generic ZTP deployment from a git repository (simply meaning that no secrets or pull secrets are included). You'll notice that a kustomization.yaml is used to control which manifests are deployed to production. Within the ztp-sno15 folder you'll find several important deployment manifests. Let me cover the important ones in more detail:

Yes, there are others but I will cover these in a more ZTP-focused post later. The manifests above are important, because we'll be using these for our demonstration today.

01-unsealed-pull-secret.yaml
This file is simply the pull secret used to pull images for OpenShift deployments. If you've ever deployed OpenShift before, than you have used this pull-secret in one way or another.

03-agentclusterinstall.yaml
AgentClusterInstall, is an object managed by the Hive Operator. What we're declaring in this manifest are a few key items for describing our cluster deployment. For example, we're declaring the version of OpenShift, what CNI we want to leverage along with CIDR ranges, what SSH public key will have access to the cluster during/after the deployment.

04-clusterdeployment.yaml
ClusterDeployment, is also an object managed by the Hive Operator. This manifest describes the name of the cluster along with base-DNS name, it declares the pull-secret used to obtain OpenShift container images, and most importantly it declares what platform the cluster will be deployed within, in this case bare metal.

07-nmstate.yaml
NMStateConfig is a declarative network configuration model, which is controlled through the OpenShift/Kubernetes API. This is used to configure the networking on an RHCOS host.

08-infraenv.yaml
InfraEnv is managed via the Infrastructure Operator, or as we typically call it the Assisted-Service (Assisted-Installer). InfraEnv can include all sorts of things from ignition overrides to proxy overrides, but in general this object tells the assisted-installer the basics of the installation request.

There you have it! These are arguably the most important artifacts required to deploy a cluster. Why did we cover these? Because we're going to create simple variations of these to deploy a sample cluster without the need for an install-config.yaml or agent.yaml.

For this one, we're going to jump right into the demonstration, but I'll continue to link other helpful posts where applicable.

Part III: Demonstration

I'm going to deploy the same exact cluster as I did in my previous blog post. The reason for doing this is to make things easy to read and follow along. So, our cluster name will still be ztp-ocpsno58. Let's create these deployment files exactly the same way, so you have some level of success, and then you can modify them to your own needs (I'll also cover some caveats with this MVP build of openshift-install agent utility.

Make sure you follow the same exact instructions prior to creating/using these manifests (consider these prerequisites):

Step 1: Download the Binary

gdown 1-rJzzyVa9rWvw3yeAuGsTfaaSFLcMY6x
tar zxvf openshift-install.tgz
sudo chmod +x openshift-install
sudo chown root:root openshift-install
sudo mv openshift-install /usr/local/bin/openshift-install
PATH=$PATH:/usr/local/bin

Step 2: Install Perquisite Packages

sudo yum install genisoimage nmstate -yy

Step 3: Create Deployment Directory Structure

Slightly different from before, you will need to create a directory structure like this for the deployment manifests:

[root@aio demo]# mkdir -p {ztp-ocpsno58/cluster-manifests,ztp-ocpsno58-backup/cluster-manifests}
[root@aio demo]# tree .
.
├── ztp-ocpsno58
│   └── cluster-manifests
└── ztp-ocpsno58-backup
    └── cluster-manifests

4 directories, 0 files
[root@aio demo]#

Step 4: Create the Following Manifests

The following manifests are mandatory. I will explain some adaptations, and where the state of things are with this MVP later in the post.

PullSecret

In the same directory above (view the tree output), write the following file:

cat << EOF > ./ztp-ocpsno58/cluster-manifests/pull-secret.yaml
---
apiVersion: v1
kind: Secret
type: kubernetes.io/dockerconfigjson
metadata:
  name: pull-ztp-ocpsno58
  namespace: cluster0
stringData:
  .dockerconfigjson: "$OPENSHIFT_PULL_SECRET"
EOF

IMPORTANT: Make sure that you've replaced $OPENSHIFT_PULL_SECRET with your actual pull secret.