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**1. What is GitOps? **

GitOps is a modern way to manage Kubernetes deployments.

Key points:

  • Git = Source of Truth → All Kubernetes manifests live in Git.
  • Declarative → You describe what you want (YAML), not how to do it.
  • Pull-based → A tool (like Argo CD) pulls from Git and updates the cluster.
  • Continuous Reconciliation → It keeps checking if the cluster matches Git, and fixes it if not.

Why GitOps?

  • Every change is tracked in Git history.
  • Easy rollbacks.
  • Fewer manual mistakes.
  • Strong security (no direct cluster access for everyone).

**2. What is Argo CD? **

Definition: Argo CD is a GitOps operator for Kubernetes that:

  • Continuously monitors a Git repo.
  • Deploys changes automatically or manually.
  • Shows visual status in a Web UI.
  • Can manage multiple clusters.

Argo CD Components:

  1. argocd-server → Web UI + API.
  2. application-controller → Syncs Git with cluster.
  3. repo-server → Fetches Git repo, processes Helm/Kustomize.
  4. Redis → Cache for performance.

**3. How Argo CD Works **

  1. You define your Kubernetes YAML in Git.
  2. Argo CD pulls those files.
  3. It compares Git (desired state) vs Cluster (live state).
  4. If different → you sync manually or auto-sync.
  5. If auto-sync + self-heal → it updates automatically.

**4. Setting up Argo CD on our AWS Kubernetes Cluster **

Step 1 – Install Argo CD

We install Argo CD in its own namespace:

kubectl create namespace argocd
kubectl apply -n argocd \
  -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml

Check if all pods are running:

kubectl get pods -n argocd

Step 2 – Access Argo CD UI

Since we’re using a self-managed kubeadm cluster, we’ll use NodePort:

kubectl -n argocd patch svc argocd-server \
  -p '{"spec":{"type":"NodePort","ports":[{"name":"https","port":443,"targetPort":8080,"nodePort":30080}]}}'


# Switch the existing service to an internet-facing ELB
kubectl patch svc argocd-server -n argocd -p '{"spec":{"type":"LoadBalancer"}}'

# (Optional but recommended) ensure it listens on 80/443 cleanly
kubectl patch svc argocd-server -n argocd --type='json' -p='[
  {"op":"replace","path":"/spec/ports/0/port","value":80},
  {"op":"replace","path":"/spec/ports/1/port","value":443}
]'

Get Node Public IP:

kubectl get nodes -o wide

Open browser:

https://<NODE_PUBLIC_IP>:30080

Note: Accept security warning (self-signed certificate).

Step 3 – Login to Argo CD

Get the admin password:

kubectl -n argocd get secret argocd-initial-admin-secret \
  -o jsonpath="{.data.password}" | base64 -d; echo
  • Username: admin
  • Password: (from above)

**5. Deploying a Sample App with Argo CD **

We will deploy the Guestbook app.

Step 1 – Prepare Namespace

kubectl create namespace dev

Step 2 – Fork the Sample Repo

Step 3 – Create App in Argo CD UI

  • Click NEW APP.

  • Fill in:

    • Application Name: guestbook-dev
    • Project: default
    • Sync Policy: Manual (first time)
    • Repository URL: (Your fork HTTPS URL)
    • Revision: main
    • Path: guestbook
    • Cluster URL: https://kubernetes.default.svc
    • Namespace: dev

Click CREATE.

Step 4 – Sync the App

  • Open the new app.
  • Click SYNC → Synchronize.
  • Argo CD will create Kubernetes resources.

Step 5 – Verify in Cluster

kubectl get pods -n dev
kubectl get svc -n dev

You should see the guestbook pods running.

**6. Auto-Sync & Self-Heal Demo **

Step 1 – Enable Auto-Sync

  • In the app → App Details → Actions → Enable Auto-Sync.
  • Check Prune and Self-Heal.

Step 2 – Change in Git → Auto Deployment

  • In your fork, edit guestbook-ui-deployment.yaml:
replicas: 1

change to:

replicas: 3
  • Commit and push.
  • Argo CD will detect the change and deploy automatically.

Step 3 – Self-Heal Manually scale in cluster:

kubectl scale deploy guestbook-ui -n dev --replicas=5
  • Wait ~1 min → Argo CD will revert it back to 3.

**7. Wrap-Up **

Summary for Students:

  • Argo CD is a GitOps tool for Kubernetes.
  • Everything comes from Git.
  • You can deploy manually or automatically.
  • Self-Heal enforces Git state on the cluster.
  • NodePort is easiest for accessing Argo CD in self-managed clusters.

8. Commands Recap

# Install Argo CD
kubectl create ns argocd
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml

# Access via NodePort
kubectl -n argocd patch svc argocd-server -p '{"spec":{"type":"NodePort","ports":[{"name":"https","port":443,"targetPort":8080,"nodePort":30080}]}}'
kubectl get nodes -o wide  # get public IP

# Get password
kubectl -n argocd get secret argocd-initial-admin-secret -o jsonpath="{.data.password}" | base64 -d; echo

# Create namespace for app
kubectl create ns dev

# Verify resources
kubectl get pods -n dev
kubectl get svc -n dev

9. Homework for Students

  • Try deploying another app from the same repo.
  • Enable auto-sync + self-heal for it.
  • Change replicas in Git and watch Argo CD update.
  • Delete a pod manually → see self-heal recreate it.