GitOps with ArgoCD in Kubernetes - Mini Project: Build & Apply

GitOps with ArgoCD

📖 Scenario: You are working as a DevOps engineer for a small company. Your team wants to use GitOps to manage Kubernetes applications. You will use ArgoCD to automatically deploy an application from a Git repository to a Kubernetes cluster.

🎯 Goal: Learn how to set up a basic ArgoCD Application resource that points to a Git repository and deploys an app to Kubernetes automatically.

📋 What You'll Learn

Create a Kubernetes namespace for ArgoCD

Create an ArgoCD Application resource with correct Git repo URL and path

Set the target cluster and namespace for deployment

Verify the application sync status with ArgoCD

💡 Why This Matters

🌍 Real World

GitOps with ArgoCD is used in real companies to automate Kubernetes app deployments from Git repositories, making deployments reliable and repeatable.

💼 Career

Knowing how to use ArgoCD for GitOps is a valuable skill for DevOps engineers and site reliability engineers working with Kubernetes.

1

Create the ArgoCD namespace

Create a Kubernetes namespace called argocd using the command kubectl create namespace argocd.

Kubernetes

# Create the argocd namespace
# Your code here

Hint

Use kubectl create namespace argocd to create the namespace.

2

Define the ArgoCD Application manifest

Create a YAML manifest file called app.yaml that defines an ArgoCD Application resource with these exact values: apiVersion: argoproj.io/v1alpha1, kind: Application, metadata.name: guestbook, spec.source.repoURL: https://github.com/argoproj/argocd-example-apps.git, spec.source.path: guestbook, spec.destination.server: https://kubernetes.default.svc, and spec.destination.namespace: default.

Kubernetes

# Write the ArgoCD Application YAML manifest in app.yaml
# Your code here

Hint

Make sure to include metadata.name as guestbook and set the spec.source.repoURL and spec.source.path exactly as given.

3

Apply the ArgoCD Application manifest

Use the command kubectl apply -f app.yaml -n argocd to create the ArgoCD Application resource in the argocd namespace.

Kubernetes

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/argoproj/argocd-example-apps.git
    path: guestbook
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default

# Apply the ArgoCD Application manifest
# Your code here

Hint

Use kubectl apply -f app.yaml -n argocd to create the Application resource.

4

Check the ArgoCD Application sync status

Run the command kubectl get applications -n argocd guestbook -o jsonpath='{.status.sync.status}' to display the sync status of the guestbook application.

Kubernetes

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/argoproj/argocd-example-apps.git
    path: guestbook
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  project: default

kubectl apply -f app.yaml -n argocd

# Check the sync status of the guestbook application
# Your code here

Hint

The output should be Synced when the application is deployed successfully.

Practice

1. What is the main purpose of using ArgoCD in a Kubernetes environment with GitOps?

easy

A. To replace Kubernetes with a new container orchestration system

B. To manually deploy applications without using Git

C. To store container images in a private registry

D. To automatically sync Kubernetes cluster state with Git repository configurations

Solution

1. Step 1: Understand GitOps concept

   GitOps uses Git as the single source of truth for application configurations.

2. Step 2: Role of ArgoCD in GitOps

   ArgoCD automatically syncs Kubernetes cluster state to match the Git repo, ensuring deployments are consistent and automated.

3. Final Answer:

   To automatically sync Kubernetes cluster state with Git repository configurations -> Option D

4. Quick Check:

   GitOps = Auto-sync cluster with Git [OK]

Hint: Remember: ArgoCD syncs cluster state from Git automatically [OK]

Common Mistakes:

• Thinking ArgoCD replaces Kubernetes
• Believing ArgoCD deploys apps manually
• Confusing ArgoCD with container registries

2. Which of the following is the correct ArgoCD CLI command to create an application named myapp syncing from Git repo https://github.com/example/repo.git with path k8s and target cluster https://kubernetes.default.svc?

easy

A. argocd app create myapp --repo https://github.com/example/repo.git --path k8s --dest-server https://kubernetes.default.svc --dest-namespace default

B. argocd create app myapp --repository https://github.com/example/repo.git --directory k8s --cluster https://kubernetes.default.svc

C. kubectl create app myapp --repo https://github.com/example/repo.git --path k8s

D. argocd app new myapp --repo-url https://github.com/example/repo.git --folder k8s --server https://kubernetes.default.svc

Solution

1. Step 1: Identify correct ArgoCD CLI syntax

   The correct command uses argocd app create with flags --repo, --path, --dest-server, and --dest-namespace.

2. Step 2: Compare options

   argocd app create myapp --repo https://github.com/example/repo.git --path k8s --dest-server https://kubernetes.default.svc --dest-namespace default matches the official syntax exactly. Others use incorrect commands or flags.

3. Final Answer:

   argocd app create myapp --repo https://github.com/example/repo.git --path k8s --dest-server https://kubernetes.default.svc --dest-namespace default -> Option A

4. Quick Check:

   Correct CLI syntax = argocd app create myapp --repo https://github.com/example/repo.git --path k8s --dest-server https://kubernetes.default.svc --dest-namespace default [OK]

Hint: Remember: 'argocd app create' plus repo, path, dest-server flags [OK]

Common Mistakes:

• Using kubectl instead of argocd CLI
• Wrong flag names like --repository or --folder
• Incorrect command order or missing --dest-namespace

3. Given the following ArgoCD Application YAML snippet, what will happen when ArgoCD syncs this app?

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: sample-app
spec:
  source:
    repoURL: https://github.com/example/app-configs.git
    path: production
  destination:
    server: https://kubernetes.default.svc
    namespace: default
  syncPolicy:
    automated: {}

medium

A. ArgoCD will reject the app because syncPolicy is empty

B. ArgoCD will only show the app status but not deploy it automatically

C. ArgoCD will automatically deploy and keep the app in sync with the Git repo

D. ArgoCD will deploy the app once but not update it on Git changes

Solution

1. Step 1: Understand syncPolicy automated

   The syncPolicy: automated: {} means ArgoCD will auto-sync changes from Git to cluster.

2. Step 2: Effect on deployment

   ArgoCD will deploy the app initially and keep it updated automatically when Git changes.

3. Final Answer:

   ArgoCD will automatically deploy and keep the app in sync with the Git repo -> Option C

4. Quick Check:

   syncPolicy automated = auto deploy and sync [OK]

Hint: syncPolicy automated means auto deploy and keep in sync [OK]

Common Mistakes:

• Thinking empty braces mean no automation
• Assuming manual sync is required
• Confusing syncPolicy with app rejection

4. You created an ArgoCD app but it shows OutOfSync status even after you committed changes to Git. Which of the following is the most likely cause?

medium

A. The app's syncPolicy is not set to automated, so manual sync is needed

B. The Git repository URL is incorrect and unreachable

C. The Kubernetes cluster is down and cannot apply changes

D. The app name in ArgoCD does not match the Git repo name

Solution

1. Step 1: Understand OutOfSync status

   OutOfSync means cluster state differs from Git repo state.

2. Step 2: Check syncPolicy effect

   If syncPolicy is not automated, ArgoCD won't auto-apply changes; manual sync is required.

3. Final Answer:

   The app's syncPolicy is not set to automated, so manual sync is needed -> Option A

4. Quick Check:

   OutOfSync + no automated sync = manual sync needed [OK]

Hint: OutOfSync often means no automated sync set [OK]

Common Mistakes:

• Assuming cluster is down without checking
• Blaming Git URL without error evidence
• Thinking app name mismatch causes OutOfSync

5. You want to ensure that ArgoCD only deploys changes to your Kubernetes cluster after manual approval, but still track changes in Git automatically. Which configuration should you use in your ArgoCD Application YAML?

hard

A. Set syncPolicy: automated: {} to enable auto deploy

B. Omit syncPolicy and use manual sync to approve changes

C. Set syncPolicy: automated: null to disable auto deploy

D. Set syncPolicy: automated: { prune: true, selfHeal: true } for auto deploy with cleanup

Solution

1. Step 1: Understand manual approval need

   To require manual approval before deployment, auto sync must be disabled.

2. Step 2: Configure syncPolicy accordingly

   Omitting syncPolicy disables auto sync, so ArgoCD tracks Git but waits for manual sync.

3. Final Answer:

   Omit syncPolicy and use manual sync to approve changes -> Option B

4. Quick Check:

   No syncPolicy = manual approval required [OK]

Hint: No syncPolicy means manual sync only [OK]

Common Mistakes:

• Using automated sync disables manual approval
• Setting automated with prune/selfHeal still auto deploys
• Setting automated: null is invalid syntax