docs: Using IAM roles instead of AWS credentails while deploying mgmt cluster

Author: Ankitasw

docs/book/src/SUMMARY_PREFIX.md

@@ -25,6 +25,7 @@
   - [Specifying the IAM Role to use for Management Components](./topics/specify-management-iam-role.md)
   - [Using external cloud provider with EBS CSI driver](./topics/external-cloud-provider-with-ebs-csi-driver.md)
   - [Restricting Cluster API to certain namespaces](./topics/restricting-cluster-api-to-certain-namespaces.md)
+  - [Using IAM roles in management cluster instead of credentials](./topics/using-iam-roles-in-mgmt-cluster.md)
   - [Failure domains](./topics/failure-domains/index.md)
     - [Control planes](./topics/failure-domains/control-planes.md)
     - [Worker nodes](./topics/failure-domains/worker-nodes.md)

docs/book/src/topics/using-iam-roles-in-mgmt-cluster.md

@@ -0,0 +1,47 @@
+# Using IAM roles in management cluster instead of AWS credentials
+
+## Overview
+
+Sometimes users might want to use IAM roles to deploy management clusters. If the user already has a management cluster which was created using the AWS credentials, CAPA provides a way to use IAM roles instead of using these credentials.
+
+## Pre-requisites
+User has a bootstrap cluster created with AWS credentials. These credentials can be temporary as well.
+To create temporary credentials, please follow [this doc](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_request.html).
+
+We can verify whether this bootstrap cluster is using AWS credentials by checking the `capa-manager-bootstrap-credentials` secret created in `capa-system` namespace:
+```bash
+kubectl get secret -n capa-system capa-manager-bootstrap-credentials -o=jsonpath='{.data.credentials}' | { base64 -d 2>/dev/null || base64 -D; }
+```
+which will give output similar to below:
+```bash
+[default]
+aws_access_key_id = <your-access-key>
+aws_secret_access_key = <your-secret-access-key>
+region = us-east-1
+
+aws_session_token = <session-token>
+```
+
+## Goal
+Create a management cluster which uses instance profiles (IAM roles) attached to EC2 instance.
+
+## Steps for CAPA-managed clusters
+1. Create a workload cluster on existing bootstrap cluster. Refer [quick start guide](https://cluster-api.sigs.k8s.io/user/quick-start.html) for more details.
+   Since only control-plane nodes have the required IAM roles attached, CAPA deployment should have the necessary tolerations for master (control-plane) node and node selector for master.
+> **Note:** A cluster with a single control plane node won’t be sufficient here due to the `NoSchedule` taint.
+
+3. Get the kubeconfig for the new target management cluster(created in previous step) once it is up and running.
+4. Zero the credentials CAPA controller started with, such that target management cluster uses empty credentials and not the previous credentials used to create bootstrap cluster using:
+```bash
+clusterawsadm controller zero-credentials --namespace=capa-system
+```
+For more details, please refer [zero-credentials doc](https://cluster-api-aws.sigs.k8s.io/clusterawsadm/clusterawsadm_controller_zero-credentials.html).
+5. Rollout and restart on capa-controller-manager deployment using:
+```bash
+clusterawsadm controller rollout-controller --kubeconfig=kubeconfig --namespace=capa-system
+```
+For more details, please refer [rollout-controller doc](https://cluster-api-aws.sigs.k8s.io/clusterawsadm/clusterawsadm_controller_rollout-controller.html).
+6. Use `clusterctl init` with the new cluster’s kubeconfig to install the provider components. For more details on preparing for init, please refer [clusterctl init doc](https://cluster-api.sigs.k8s.io/clusterctl/commands/init.html).
+7. Use `clusterctl move` to move the Cluster API resources from the bootstrap cluster to the target management cluster. For more details on preparing for move, please refer [clusterctl move doc](https://cluster-api.sigs.k8s.io/clusterctl/commands/move.html).
+8. Once the resources are moved to target management cluster successfully, `capa-manager-bootstrap-credentials` will be created as nil, and hence CAPA controllers will fall back to use the attached instance profiles.
+9. Delete the bootstrap cluster with the AWS credentials.