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World K7: Self-Driving

Sync: from Git to cluster

You will learn: what sync does, and how to read Argo CD's two status lights.

Checked with Kubernetes 1.37 on 31 Oct 2026

The problem

You merged a new version at 12:00. At 12:01, the cluster still runs the old one. Is something broken?

Try it

Ship version 1.5.0 through Git. Watch both lights: sync: Copy the order board onto the floor: make the cluster match what Git says. (does the cluster match Git?) and health (does it work?).

Change one line in Git and commit. Watch the cluster follow.

Git (the order board)

apps/shop/deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
name: shop
spec:
replicas: 3
# selector and template: same as before
image:
Show the whole file
apiVersion: apps/v1
kind: Deployment
metadata:
  name: shop
  namespace: shop
spec:
  replicas: 3
  selector:
    matchLabels:
      app: shop
  template:
    metadata:
      labels:
        app: shop
    spec:
      containers:
        - name: web
          image: ghcr.io/kedai-kancil/shop:1.4.0

Commits

  1. f89a8e9 Add shopin the cluster

Cluster · namespace shop

Sync: SyncedHealth: Healthy

Deployment shop: 3/3 ready · image 1.4.0

Manual change (drift)
syncPolicy:
  automated:
    selfHeal: true
Show the Argo CD Application
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: shop
  namespace: argocd
spec:
  project: default
  source:
    repoURL: "https://github.com/kedai-kancil/gitops.git"
    path: apps/shop
    targetRevision: main
  destination:
    server: "https://kubernetes.default.svc"
    namespace: shop
  syncPolicy:
    automated:
      selfHeal: true
Nothing to do. Git and the cluster match.

Try it

Put one sync in order.

First step at the top. Put these in order. Use the arrows, or drag.

  • Argo CD applies the files: Syncing
  • Synced and Healthy
  • You merge a commit in Git
  • New pods start: Progressing
  • Argo CD notices: OutOfSync

Watch

Argo CD shows two separate lights. Sort each word into the right light.

Drag a card into a box. Or tap the card, then tap the box.

      Try it

      A teammate’s commit made sync fail. Argo CD shows the same error kubectl apply gives. Fix the file in Git.

      Fix the manifest, then press Apply.

      shop.yaml18 lines

      Predict

      Argo CD shows Synced, but Degraded. What does that mean?

      Check

      Swipe: true or not quite?

      Swipe right for good, left for needs work. Or use the buttons.

      1 / 3

      A webhook from GitHub can make Argo CD sync at once.

      You did it!

      You can now read a sync, light by light.

      Go deeper (optional)

      Sync can be automated or manual. Manual sync waits for a button or argocd app sync shop. With prune: true, objects you delete from Git are deleted from the cluster too. Real rep (optional): install Argo CD on a throwaway kind cluster. Watch an example app sync. Mission 6 walks you through it.