Define container environment variables using Secret data (#13800)

* Example for injecting single secret as env variable

Define a container environment variable with data from a single Secret

* Env variable using secret data

* Update pod-single-secret-env-variable.yaml

* Adding example for multiple env variable using secrets

Adding example for multiple env variables using secrets

* Create pod-secret-envFrom.yaml

* Update pod-multiple-secret-env-variable.yaml

* Update pod-multiple-secret-env-variable.yaml

* Update pod-multiple-secret-env-variable.yaml

* Update pod-single-secret-env-variable.yaml

* Update pod-multiple-secret-env-variable.yaml

* Update pod-single-secret-env-variable.yaml

* Different ways to add env variable using secret

Adding different ways to add env variable in pod using secret

* Correcting formatting issues

Correcting formatting issues

* Correcting format issue

content/en/docs/tasks/inject-data-application/distribute-credentials-secure.md

@@ -143,48 +143,78 @@ is exposed:
     my-app
     39528$vdg7Jb
     ```
-
-## Create a Pod that has access to the secret data through environment variables
-
-Here is a configuration file you can use to create a Pod:
-
-{{< codenew file="pods/inject/secret-envars-pod.yaml" >}}
-
-1. Create the Pod:
-
-    ```shell
-    kubectl apply -f https://k8s.io/examples/pods/inject/secret-envars-pod.yaml
-    ```
-
-1. Verify that your Pod is running:
-    ```shell
-    kubectl get pod secret-envars-test-pod
-    ```
-
-    Output:
-    ```shell
-    NAME                     READY     STATUS    RESTARTS   AGE
-    secret-envars-test-pod   1/1       Running   0          4m
-    ```
-
-1. Get a shell into the Container that is running in your Pod:
-    ```shell
-    kubectl exec -it secret-envars-test-pod -- /bin/bash
-    ```
-
-1. In your shell, display the environment variables:
-    ```shell
-    root@secret-envars-test-pod:/# printenv
-    ```
-
-    The output includes your username and password:
-    ```shell
-    ...
-    SECRET_USERNAME=my-app
-    ...
-    SECRET_PASSWORD=39528$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:
+
+   ```shell
+   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.   
+   
+   {{< codenew file="pods/inject/pod-single-secret-env-variable.yaml" >}}
+   
+*  Create the Pod:	
+
+   ```shell
+   kubectl create -f https://k8s.io/examples/pods/inject/pod-single-secret-env-variable.yaml
+   ```
+   
+*  Now, the Pod’s output includes environment variable `SECRET_USERNAME=backend-admin`
+
+
+### Define container environment variables with data from multiple Secrets
+
+*  As with the previous example, create the Secrets first.
+  
+   ```shell
+     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.   
+   
+   {{< codenew file="pods/inject/pod-multiple-secret-env-variable.yaml" >}}
+   
+*  Create the Pod:
+
+   ```shell
+   kubectl create -f https://k8s.io/examples/pods/inject/pod-multiple-secret-env-variable.yaml 
+   ```
+   
+*  Now, the Pod’s output includes `BACKEND_USERNAME=backend-admin` and `DB_USERNAME=db-admin` environment variables. 	 
+
+
+## Configure all key-value pairs in a Secret as container environment variables
+
+{{< note >}}
+This functionality is available in Kubernetes v1.6 and later.
+{{< /note >}}
+
+*  Create a Secret containing multiple key-value pairs
+   
+   ```shell
+   kubectl create secret generic test-secret --from-literal=username='my-app' --from-literal=password='39528$vdg7Jb'
+   ```
+   
+*  Use envFrom to define all of the Secret’s data as container environment variables. The key from the Secret becomes the environment      variable name in the Pod.   
+
+    {{< codenew file="pods/inject/pod-secret-envFrom.yaml" >}}
+   
+*  Create the Pod:
+
+   ```shell
+   kubectl create -f https://k8s.io/examples/pods/inject/pod-secret-envFrom.yaml
+   ```
+ 
+*  Now, the Pod’s output includes `username=my-app` and `password=39528$vdg7Jb` environment variables.  
+   
+     
 {{% /capture %}}
 
 {{% capture whatsnext %}}

content/en/examples/pods/inject/pod-multiple-secret-env-variable.yaml

@@ -0,0 +1,19 @@
+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

content/en/examples/pods/inject/pod-secret-envFrom.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: envfrom-secret
+spec:
+  containers:
+  - name: envars-test-container
+    image: nginx
+    envFrom:
+    - secretRef:
+        name: test-secret

content/en/examples/pods/inject/pod-single-secret-env-variable.yaml

@@ -0,0 +1,14 @@
+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