Add instructions on how to bootstrap the cluster fleet

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

README.md

@@ -1,2 +1,152 @@
 # flux2-hub-spoke-example
-A hub-and-spoke example for multi-cluster continuous delivery with Flux
+
+This repository showcases how to run Flux on a central Kubernetes cluster
+and have it manage the GitOps continuous delivery of apps and infrastructure
+workloads on multiple clusters.
+
+## Prerequisites
+
+For this example, you need to install the following tools:
+
+- [Flux CLI](https://fluxcd.io/flux/installation/#install-the-flux-cli)
+- [Kubernetes KinD](https://kind.sigs.k8s.io/docs/user/quick-start/#installation)
+- kubectl and kustomize
+
+On macOS and Linux, you can install the tools using the following commands:
+
+```bash
+brew install fluxcd/tap/flux
+brew install kind kubectl kustomize
+```
+
+In order to follow the guide you'll need a GitHub account and a
+[personal access token](https://help.github.com/en/github/authenticating-to-github/creating-a-personal-access-token-for-the-command-line)
+that can create repositories (check all permissions under `repo`).
+
+## Repository structure
+
+The Git repository contains the following top directories:
+
+- `deploy` dir contains the HelmRelease definitions for the apps and infrastructure workloads
+- `clusters` dir contains the apps and infrastructure Kustomize overlays for each target cluster
+- `hub` dir contains the Flux configuration for the central cluster and targets
+
+```shell
+├── deploy
+│   ├── apps
+│   │   ├── podinfo.yaml
+│   │   └── kustomization.yaml
+│   ├── infra-configs
+│   │   ├── cluster-issuers.yaml
+│   │   └── kustomization.yaml
+│   ├── infra-controllers
+│   │   ├── cert-manager.yaml
+│   │   ├── ingress-nginx.yaml
+│   │   └── kustomization.yaml
+│   └── tenants
+├── clusters
+│   ├── production
+│   └── staging
+│       ├── apps
+│       │   ├── kustomization.yaml
+│       │   └── podinfo-values.yaml
+│       ├── infra-configs
+│       ├── infra-controllers
+│       └── tenants
+└── hub
+    ├── flux-system
+    ├── production.yaml
+    └── staging.yaml
+```
+
+## Bootstrap the cluster fleet
+
+To bootstrap the cluster fleet, first you need to create several Kubernetes KinD
+clusters by running the following command:
+
+```shell
+make fleet-up
+```
+
+The above command will create the following clusters:
+
+- `flux-hub` - the central cluster where Flux will run
+- `flux-staging` - the target cluster where Flux will deploy the `clusters/staging` workloads
+- `flux-production` - the target cluster where Flux will deploy the `clusters/production` workloads
+
+After the clusters are created, kubeconfig files for staging and production are generated and persisted
+in the `flux-hub` cluster, so that Flux can access the target clusters.
+
+```console
+$ kubectl get secrets -A
+NAMESPACE     NAME                     TYPE
+production    cluster-kubeconfig       Opaque
+staging       cluster-kubeconfig       Opaque
+```
+
+Fork this repository on your personal GitHub account and
+export your GitHub access token, username and repo name:
+
+```shell
+export GITHUB_TOKEN=<your-token>
+export GITHUB_USER=<your-username>
+export GITHUB_REPO=<repository-name>
+```
+
+Then, bootstrap Flux on the hub cluster:
+
+```shell
+flux bootstrap github \
+    --context=kind-flux-hub \
+    --owner=${GITHUB_USER} \
+    --repository=${GITHUB_REPO} \
+    --branch=main \
+    --personal \
+    --path=hub
+```
+
+The bootstrap command commits the manifests for the Flux components in `hub/flux-system` dir
+and creates a deploy key with read-only access on GitHub, so it can pull changes inside the cluster.
+
+Wait for the Flux to reconcile the infrastructure and apps workloads on the target clusters with:
+
+```shell
+watch flux get kustomizations -A
+```
+
+Once the Flux Kustomizations are ready, you can list the workloads deployed in the target clusters.
+For example, in the staging cluster:
+
+```console
+$ kubectl --context kind-flux-staging get pods -A
+NAMESPACE            NAME                                                 READY
+cert-manager         cert-manager-6dc66985d4-fkv95                        1/1
+cert-manager         cert-manager-cainjector-c7d4dbdd9-2kr6f              1/1
+cert-manager         cert-manager-webhook-847d7676c9-vqn6f                1/1
+ingress-nginx        ingress-nginx-controller-55474d95c5-mq8mj            1/1
+podinfo              podinfo-66f4ccb98c-bt99t                             1/1
+```
+
+## Testing
+
+After making changes to the manifests, you can validate them locally with [kubeconform](https://github.com/yannh/kubeconform) by running:
+
+```shell
+make validate
+```
+
+Any change to the Kubernetes manifests or to the repository structure should be validated in CI before
+a pull requests is merged into the main branch and synced on the cluster.
+
+This repository contains the following GitHub CI workflows:
+
+* the [test](./.github/workflows/test.yaml) workflow validates the Kubernetes manifests and Kustomize overlays are conformant with the Flux OpenAPI spec 
+* the [e2e](./.github/workflows/e2e.yaml) workflow starts the Kubernetes cluster fleet in CI and tests the setup by running Flux in Kubernetes Kind
+
+## Teardown
+
+To delete the cluster fleet, run the following command:
+
+```shell
+make fleet-down
+```