✅ Scenario #14 – Integrate Kubernetes with Vault to fetch Secrets

This content originally appeared on DEV Community and was authored by Latchu@DevOps

Goal: A Kubernetes Pod can automatically fetch secrets from Vault using Kubernetes ServiceAccount authentication (no static tokens).

High-Level Flow

1. Install Vault on Kubernetes
2. Initialize & unseal Vault (Dev mode auto-unsealed)
3. Enable Kubernetes Auth
4. Configure Vault to trust Kubernetes
5. Create a Vault policy
6. Create a Kubernetes ServiceAccount
7. Map Kubernetes SA → Vault role
8. Deploy a Pod that auto-fetches secrets from Vault
9. Verify secrets are injected inside the pod

Prerequisites

GKE cluster running
kubectl configured
helm installed (Cloud Shell already has it)

STEP 1 — Install Vault on Kubernetes

Add HashiCorp Helm repo

helm repo add hashicorp https://helm.releases.hashicorp.com
helm repo update

Create namespace

kubectl create namespace vault

Install Vault in dev mode (auto-unseal)

helm install vault hashicorp/vault \
  --namespace vault \
  --set "server.dev.enabled=true"

Check pod:

kubectl get pods -n vault

You should see:

vault-0   Running

STEP 2 — Exec into Vault Pod

kubectl exec -it vault-0 -n vault -- /bin/sh

Set Vault address inside pod:

export VAULT_ADDR="http://127.0.0.1:8200"

Check status:

vault status

STEP 3 — Enable Kubernetes Authentication

Inside the Vault pod:

vault auth enable kubernetes

STEP 4 — Configure Kubernetes Auth Method

Vault needs:

• Token reviewer JWT
• Kubernetes API server URL
• Kubernetes CA cert

Inside the pod:

vault write auth/kubernetes/config \
  token_reviewer_jwt="$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" \
  kubernetes_host="https://${KUBERNETES_PORT_443_TCP_ADDR}:443" \
  kubernetes_ca_cert=@/var/run/secrets/kubernetes.io/serviceaccount/ca.crt

This will work now because you’re inside a Kubernetes pod.

STEP 5 — Create a Secret in Vault

Inside Vault pod:

vault kv put secret/myapp username="admin" password="P@ssw0rd123"

Verify:

vault kv get secret/myapp

STEP 6 — Create Vault Policy

Create a file inside Vault pod:

cd /tmp
cat <<EOF > myapp-policy.hcl
path "secret/data/myapp" {
  capabilities = ["read"]
}
EOF

Load the policy:

vault policy write myapp-policy /tmp/myapp-policy.hcl

STEP 7 — Create Kubernetes ServiceAccount

Exit the Vault pod:

exit

Create SA in default namespace:

kubectl create sa myapp-sa

STEP 8 — Create Vault Role that maps SA → Policy

Go back into Vault pod:

kubectl exec -it vault-0 -n vault -- /bin/sh
export VAULT_ADDR="http://127.0.0.1:8200"

Now create the role:

vault write auth/kubernetes/role/myapp-role \
  bound_service_account_names="myapp-sa" \
  bound_service_account_namespaces="default" \
  policies="myapp-policy" \
  ttl="24h"

STEP 9 — Deploy Application That Fetches Secrets Automatically

Outside Vault pod.

Create a deployment using Vault Agent injector.

Create a file:

cat <<EOF > myapp.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  replicas: 1
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
      annotations:
        vault.hashicorp.com/agent-inject: "true"
        vault.hashicorp.com/role: "myapp-role"
        vault.hashicorp.com/agent-inject-secret-mysecret: "secret/myapp"
    spec:
      serviceAccountName: myapp-sa
      containers:
      - name: myapp
        image: nginx
EOF

Apply:

kubectl apply -f myapp.yaml

STEP 10 — Verify Vault Injected Secrets

Wait for pod:

kubectl get pods

Get the pod name:

myapp-xxxxxxxx

Exec into it:

kubectl exec -it myapp-xxxxx -- /bin/sh

List injected secrets:

ls /vault/secrets

You should see:

mysecret

View content:

cat /vault/secrets/mysecret

You will see:

{
  "username": "admin",
  "password": "P@ssw0rd123"
}

SUCCESS — Kubernetes Pod securely pulled secrets from Vault!

Thanks for reading! If this post added value, a like , follow, or share would encourage me to keep creating more content.

— Latchu | Senior DevOps & Cloud Engineer

AWS | GCP | Kubernetes | Security | Automation
Sharing hands-on guides, best practices & real-world cloud solutions

This content originally appeared on DEV Community and was authored by Latchu@DevOps