Argo CD Pocket Book

Posted on by uplatzblog

Argo CD Pocket Book — Uplatz

60+ deep-dive flashcards • GitOps • Kubernetes CD • Security & RBAC • Multi-Cluster • Observability • Interview Q&A

Cheat-friendly snippets • Real-world deployment tips • Production scaling patterns

Section 1 — Fundamentals

1) What is Argo CD?

Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. It syncs Kubernetes clusters with the desired application state stored in Git repositories.

2) Why GitOps?

✔️ Single source of truth (Git)
✔️ Auditable deployments
✔️ Rollbacks via Git commits
✔️ Declarative & automated.

3) Argo CD Components

  • API Server
  • Repo Server
  • Application Controller
  • UI (Web + CLI)

4) Installation

kubectl create namespace argocd
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml
kubectl port-forward svc/argocd-server -n argocd 8080:443

5) First Login

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

Default user: admin

Section 2 — Core Usage

6) Creating an Application

argocd app create guestbook \
  --repo https://github.com/argoproj/argocd-example-apps.git \
  --path guestbook \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace default

7) Syncing an Application

argocd app sync guestbook

8) Rollback

Argo CD can rollback to a previous Git commit, ensuring reproducibility and safety.

argocd app rollback guestbook 1

9) Health Status

Applications show health: Healthy, Progressing, Degraded, Missing, or Unknown.

10) Sync Strategies

✔ Manual sync
✔ Automatic sync
✔ Self-heal mode
✔ Prune (remove extra resources).

Section 3 — GitOps Patterns

11) App of Apps Pattern

A meta-application manages multiple child apps by pointing to their manifests in Git. Simplifies multi-app deployments.

12) Multi-Cluster Deployments

Argo CD can deploy to multiple Kubernetes clusters by registering cluster contexts.

argocd cluster add CONTEXT

13) Helm Charts

Argo CD supports deploying Helm charts directly.

argocd app create myapp --repo https://charts.helm.sh/stable --helm-chart nginx

14) Kustomize

Native support for Kustomize overlays, enabling environment-specific configurations.

15) Directory Repos

Argo CD can watch plain YAML/K8s manifests in a Git directory without Helm/Kustomize.

Section 4 — Security & RBAC

16) RBAC

Role-based policies for read/write access. Define in argocd-rbac-cm ConfigMap.

17) SSO

Argo CD integrates with SSO providers (OIDC, SAML, LDAP, GitHub OAuth).

18) Secrets Management

Integrate with external secret stores like HashiCorp Vault, AWS Secrets Manager, or SealedSecrets.

19) Network Policies

Use Kubernetes NetworkPolicies to restrict communication of Argo CD pods.

20) Best Practices

  • Use least privilege RBAC
  • Audit sync/rollback actions
  • Enable TLS for all endpoints

Section 5 — Observability & Scaling

21) Metrics

Argo CD exposes Prometheus metrics via the /metrics endpoint.

22) Logging

Logs are emitted via standard Kubernetes logging. Aggregate with ELK, Loki, or CloudWatch.

23) Notifications

Argo CD Notifications plugin integrates with Slack, Teams, Email, and Webhooks for sync events.

24) Scaling

Run multiple Application Controllers for HA. Use Redis HA for caching.

25) Performance Tuning

  • Reduce repo size with shallow clones
  • Enable parallel sync
  • Shard by namespace

Section 6 — Interview Q&A

26) Q: Argo CD vs Jenkins?

Answer: Jenkins is CI-focused, Argo CD is CD-focused with GitOps. They complement each other: Jenkins builds → Argo deploys.

27) Q: Argo CD vs Flux?

Answer: Both are GitOps CD tools. Argo CD has a rich UI and RBAC, while Flux is CLI-first and lighter.

28) Q: How does self-heal work?

Answer: If the cluster state drifts from Git, Argo CD automatically syncs resources back to the desired state.

29) Q: Can Argo CD manage non-K8s?

Answer: No, it is Kubernetes-native. Non-K8s infra requires tools like Terraform + Atlantis.

30) Q: How to improve Argo CD security?

Answer: Use TLS, RBAC, SSO, external secrets, audit logs, and isolate Argo CD namespace.