GitOps with ArgoCD Beginner Guide

Git Repo (desired state) → ArgoCD → Kubernetes Cluster (actual state)
                              ↓
                    Detects drift, syncs automatically

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

# Wait for pods
kubectl -n argocd rollout status deployment argocd-server

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

# Access UI
kubectl port-forward svc/argocd-server -n argocd 8080:443
# Open https://localhost:8080

# macOS
brew install argocd

# Linux
curl -sSL -o argocd https://github.com/argoproj/argo-cd/releases/latest/download/argocd-linux-amd64
chmod +x argocd
sudo mv argocd /usr/local/bin/

# Login
argocd login localhost:8080

argocd app create my-app \
  --repo https://github.com/myorg/k8s-manifests.git \
  --path apps/my-app \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace production \
  --sync-policy automated \
  --auto-prune \
  --self-heal

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/k8s-manifests.git
    targetRevision: main
    path: apps/my-app
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true       # Delete resources removed from Git
      selfHeal: true    # Revert manual changes
    syncOptions:
      - CreateNamespace=true
    retry:
      limit: 3
      backoff:
        duration: 5s
        maxDuration: 3m
        factor: 2

k8s-manifests/
  apps/
    my-app/
      deployment.yaml
      service.yaml
      ingress.yaml
      configmap.yaml
    api/
      deployment.yaml
      service.yaml
    worker/
      deployment.yaml
  base/
    namespace.yaml
    network-policies.yaml

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: prometheus
  namespace: argocd
spec:
  source:
    repoURL: https://prometheus-community.github.io/helm-charts
    chart: kube-prometheus-stack
    targetRevision: 55.0.0
    helm:
      values: |
        grafana:
          enabled: true
          adminPassword: admin
        prometheus:
          prometheusSpec:
            retention: 30d
            storageSpec:
              volumeClaimTemplate:
                spec:
                  resources:
                    requests:
                      storage: 50Gi
  destination:
    server: https://kubernetes.default.svc
    namespace: monitoring

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app-production
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/myorg/k8s-manifests.git
    targetRevision: main
    path: overlays/production
  destination:
    server: https://kubernetes.default.svc
    namespace: production

# apps/root-app.yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: root
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/myorg/k8s-manifests.git
    path: argocd-apps    # Directory containing Application manifests
  destination:
    server: https://kubernetes.default.svc
    namespace: argocd
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

argocd-apps/
  my-app.yaml          # Application manifest
  api.yaml             # Application manifest
  prometheus.yaml      # Application manifest
  cert-manager.yaml    # Application manifest

# List apps
argocd app list

# Get app details
argocd app get my-app

# Sync
argocd app sync my-app

# Diff (what would change)
argocd app diff my-app

# History
argocd app history my-app

# Rollback
argocd app rollback my-app REVISION_NUMBER

# Delete app (and resources)
argocd app delete my-app --cascade

# GitHub Actions — update image tag in Git
- name: Update image tag
  run: |
    cd k8s-manifests
    kustomize edit set image my-app=my-registry/my-app:${{ github.sha }}
    git add .
    git commit -m "deploy: my-app ${{ github.sha }}"
    git push