Distribute Credentials Securely Using Secrets

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

echo -n 'my-app' | base64
echo -n '39528$vdg7Jb' | base64

pods/inject/secret.yaml

apiVersion: v1
kind: Secret
metadata:
  name: test-secret
data:
  username: bXktYXBw
  password: Mzk1MjgkdmRnN0pi

1. Create the Secret

   kubectl apply -f https://k8s.io/examples/pods/inject/secret.yaml
   

2. View information about the Secret:

   kubectl get secret test-secret
   

   Output:

   NAME          TYPE      DATA      AGE
   test-secret   Opaque    2         1m
   

3. View more detailed information about the Secret:

   kubectl describe secret test-secret
   

   Output:

   Name:       test-secret
   Namespace:  default
   Labels:     <none>
   Annotations:    <none>
   
   Type:   Opaque
   
   Data
   ====
   password:   13 bytes
   username:   7 bytes
   

Create a Secret directly with kubectl

If you want to skip the Base64 encoding step, you can create the same Secret using the kubectl create secret command. For example:

kubectl create secret generic test-secret --from-literal='username=my-app' --from-literal='password=39528$vdg7Jb'

This is more convenient. The detailed approach shown earlier runs through each step explicitly to demonstrate what is happening.

Create a Pod that has access to the secret data through a Volume

Here is a configuration file you can use to create a Pod:

pods/inject/secret-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: secret-test-pod
spec:
  containers:
    - name: test-container
      image: nginx
      volumeMounts:
        # name must match the volume name below
        - name: secret-volume
          mountPath: /etc/secret-volume
  # The secret data is exposed to Containers in the Pod through a Volume.
  volumes:
    - name: secret-volume
      secret:
        secretName: test-secret

1. Create the Pod:

   kubectl apply -f https://k8s.io/examples/pods/inject/secret-pod.yaml
   

2. Verify that your Pod is running:

   kubectl get pod secret-test-pod
   

   Output:

   NAME              READY     STATUS    RESTARTS   AGE
   secret-test-pod   1/1       Running   0          42m
   

3. Get a shell into the Container that is running in your Pod:

   kubectl exec -i -t secret-test-pod -- /bin/bash
   

4. The secret data is exposed to the Container through a Volume mounted under /etc/secret-volume.

   In your shell, list the files in the /etc/secret-volume directory:

   # Run this in the shell inside the container
   ls /etc/secret-volume
   

   The output shows two files, one for each piece of secret data:

   password username
   

5. In your shell, display the contents of the username and password files:

   # Run this in the shell inside the container
   echo "$( cat /etc/secret-volume/username )"
   echo "$( cat /etc/secret-volume/password )"
   

   The output is your username and password:

   my-app
   39528$vdg7Jb
   

Define container environment variables using Secret data

Define a container environment variable with data from a single Secret

• Define an environment variable as a key-value pair in a Secret:

  kubectl create secret generic backend-user --from-literal=backend-username='backend-admin'
  

• Assign the backend-username value defined in the Secret to the SECRET_USERNAME environment variable in the Pod specification.

  pods/inject/pod-single-secret-env-variable.yaml

  apiVersion: v1
  kind: Pod
  metadata:
    name: env-single-secret
  spec:
    containers:
    - name: envars-test-container
      image: nginx
      env:
      - name: SECRET_USERNAME
        valueFrom:
          secretKeyRef:
            name: backend-user
            key: backend-username
  

• Create the Pod:

  kubectl create -f https://k8s.io/examples/pods/inject/pod-single-secret-env-variable.yaml
  

• In your shell, display the content of SECRET_USERNAME container environment variable

  kubectl exec -i -t env-single-secret -- /bin/sh -c 'echo $SECRET_USERNAME'
  

  The output is

  backend-admin
  

Define container environment variables with data from multiple Secrets

• As with the previous example, create the Secrets first.

  kubectl create secret generic backend-user --from-literal=backend-username='backend-admin'
  kubectl create secret generic db-user --from-literal=db-username='db-admin'
  

• Define the environment variables in the Pod specification.

  pods/inject/pod-multiple-secret-env-variable.yaml

  apiVersion: v1
  kind: Pod
  metadata:
    name: envvars-multiple-secrets
  spec:
    containers:
    - name: envars-test-container
      image: nginx
      env:
      - name: BACKEND_USERNAME
        valueFrom:
          secretKeyRef:
            name: backend-user
            key: backend-username
      - name: DB_USERNAME
        valueFrom:
          secretKeyRef:
            name: db-user
            key: db-username
  

• Create the Pod:

  kubectl create -f https://k8s.io/examples/pods/inject/pod-multiple-secret-env-variable.yaml
  

• In your shell, display the container environment variables

  kubectl exec -i -t envvars-multiple-secrets -- /bin/sh -c 'env | grep _USERNAME'
  

  The output is

  DB_USERNAME=db-admin
  BACKEND_USERNAME=backend-admin
  

Configure all key-value pairs in a Secret as container environment variables

• Create a Secret containing multiple key-value pairs

  kubectl create secret generic test-secret --from-literal=username='my-app' --from-literal=password='39528$vdg7Jb'
  

• Use envFrom to define all of the Secret's data as container environment variables. The key from the Secret becomes the environment variable name in the Pod.

  pods/inject/pod-secret-envFrom.yaml

  apiVersion: v1
  kind: Pod
  metadata:
    name: envfrom-secret
  spec:
    containers:
    - name: envars-test-container
      image: nginx
      envFrom:
      - secretRef:
          name: test-secret
  

• Create the Pod:

  kubectl create -f https://k8s.io/examples/pods/inject/pod-secret-envFrom.yaml
  

• In your shell, display username and password container environment variables

  kubectl exec -i -t envfrom-secret -- /bin/sh -c 'echo "username: $username\npassword: $password\n"'
  

  The output is

  username: my-app
  password: 39528$vdg7Jb
  

References

• Secret
• Volume
• Pod

What's next

• Learn more about Secrets.
• Learn about Volumes.