Merge pull request #20439 from AlphaWong/patch-1

Add example for secret.md for `envFrom` field

Author: k8s-ci-robot

content/en/docs/concepts/configuration/secret.md

@@ -854,6 +854,43 @@ start until all the Pod's volumes are mounted.
 
 ## Use cases
 
+### Use-Case: As container environment variables
+
+Create a secret
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: mysecret
+type: Opaque
+data:
+  USER_NAME: YWRtaW4=
+  PASSWORD: MWYyZDFlMmU2N2Rm
+```
+
+Create the Secret:
+```shell
+kubectl apply -f mysecret.yaml
+```
+
+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.
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: secret-test-pod
+spec:
+  containers:
+    - name: test-container
+      image: k8s.gcr.io/busybox
+      command: [ "/bin/sh", "-c", "env" ]
+      envFrom:
+      - secretRef:
+          name: mysecret
+  restartPolicy: Never
+```
+
 ### Use-Case: Pod with ssh keys
 
 Create a secret containing some ssh keys: