Argo CD

Argo CD is a declarative GitOps continuous delivery tool for Kubernetes that syncs application state from Git repositories.

Installation

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

# Install CLI
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/

# Get initial admin password
argocd admin initial-password -n argocd

# Login
argocd login argocd.example.com --grpc-web

Application Definitions

yaml
# apps/web-app.yaml — Basic ArgoCD Application manifest
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: web-app
  namespace: argocd
  finalizers:
    - resources-finalizer.argocd.argoproj.io
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/web-app.git
    targetRevision: main
    path: k8s/overlays/production
  destination:
    server: https://kubernetes.default.svc
    namespace: web-app
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
      allowEmpty: false
    syncOptions:
      - CreateNamespace=true
      - PrunePropagationPolicy=foreground
      - PruneLast=true
    retry:
      limit: 5
      backoff:
        duration: 5s
        factor: 2
        maxDuration: 3m

yaml
# apps/helm-app.yaml — Application using Helm chart source
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: monitoring
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://prometheus-community.github.io/helm-charts
    chart: kube-prometheus-stack
    targetRevision: 55.0.0
    helm:
      releaseName: monitoring
      valuesObject:
        grafana:
          enabled: true
          ingress:
            enabled: true
            hosts:
              - grafana.example.com
        prometheus:
          prometheusSpec:
            retention: 30d
            storageSpec:
              volumeClaimTemplate:
                spec:
                  accessModes: ["ReadWriteOnce"]
                  resources:
                    requests:
                      storage: 50Gi
  destination:
    server: https://kubernetes.default.svc
    namespace: monitoring
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
      - CreateNamespace=true
      - ServerSideApply=true

App of Apps Pattern

yaml
# apps/root-app.yaml — Root application that manages other apps
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: root-app
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/gitops-config.git
    targetRevision: main
    path: apps
  destination:
    server: https://kubernetes.default.svc
    namespace: argocd
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

ApplicationSet

yaml
# appsets/multi-cluster.yaml — Deploy to multiple clusters automatically
apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: web-app-set
  namespace: argocd
spec:
  generators:
    - clusters:
        selector:
          matchLabels:
            environment: production
  template:
    metadata:
      name: "web-app-{{name}}"
    spec:
      project: default
      source:
        repoURL: https://github.com/myorg/web-app.git
        targetRevision: main
        path: k8s/overlays/production
      destination:
        server: "{{server}}"
        namespace: web-app
      syncPolicy:
        automated:
          prune: true
          selfHeal: true

Projects

yaml
# projects/team-a.yaml — ArgoCD project with RBAC restrictions
apiVersion: argoproj.io/v1alpha1
kind: AppProject
metadata:
  name: team-a
  namespace: argocd
spec:
  description: "Team A applications"
  sourceRepos:
    - "https://github.com/myorg/team-a-*"
  destinations:
    - namespace: "team-a-*"
      server: https://kubernetes.default.svc
  clusterResourceWhitelist:
    - group: ""
      kind: Namespace
  namespaceResourceBlacklist:
    - group: ""
      kind: ResourceQuota
    - group: ""
      kind: LimitRange
  roles:
    - name: developer
      policies:
        - p, proj:team-a:developer, applications, get, team-a/*, allow
        - p, proj:team-a:developer, applications, sync, team-a/*, allow
      groups:
        - team-a-devs

Sync Waves and Hooks

yaml
# k8s/namespace.yaml — Resource with sync wave annotation
apiVersion: v1
kind: Namespace
metadata:
  name: web-app
  annotations:
    argocd.argoproj.io/sync-wave: "-1"
---
# k8s/migration-job.yaml — Pre-sync hook for database migration
apiVersion: batch/v1
kind: Job
metadata:
  name: db-migrate
  annotations:
    argocd.argoproj.io/hook: PreSync
    argocd.argoproj.io/hook-delete-policy: HookSucceeded
spec:
  template:
    spec:
      containers:
        - name: migrate
          image: myregistry.com/web-app:latest
          command: ["python", "manage.py", "migrate"]
      restartPolicy: Never

Common Commands

bash
# Application management
argocd app create web-app -f apps/web-app.yaml
argocd app list
argocd app get web-app
argocd app sync web-app
argocd app sync web-app --force --prune
argocd app delete web-app --cascade

# Diff and history
argocd app diff web-app
argocd app history web-app
argocd app rollback web-app <history-id>

# Repository management
argocd repo add https://github.com/myorg/config.git --username git --password $TOKEN
argocd repo list

# Cluster management
argocd cluster add my-cluster-context
argocd cluster list

# Account management
argocd account update-password
argocd account list