Use busybox image v1.28 for DNS related examples (#13336)

content/en/docs/concepts/services-networking/dns-pod-service.md

@@ -112,7 +112,7 @@ spec:
   hostname: busybox-1
   subdomain: default-subdomain
   containers:
-  - image: busybox
+  - image: busybox:1.28
     command:
       - sleep
       - "3600"
@@ -128,7 +128,7 @@ spec:
   hostname: busybox-2
   subdomain: default-subdomain
   containers:
-  - image: busybox
+  - image: busybox:1.28
     command:
       - sleep
       - "3600"
@@ -192,7 +192,7 @@ metadata:
   namespace: default
 spec:
   containers:
-  - image: busybox
+  - image: busybox:1.28
     command:
       - sleep
       - "3600"

content/en/docs/concepts/workloads/pods/init-containers.md

@@ -112,19 +112,19 @@ metadata:
     pod.beta.kubernetes.io/init-containers: '[
         {
             "name": "init-myservice",
-            "image": "busybox",
+            "image": "busybox:1.28",
             "command": ["sh", "-c", "until nslookup myservice; do echo waiting for myservice; sleep 2; done;"]
         },
         {
             "name": "init-mydb",
-            "image": "busybox",
+            "image": "busybox:1.28",
             "command": ["sh", "-c", "until nslookup mydb; do echo waiting for mydb; sleep 2; done;"]
         }
     ]'
 spec:
   containers:
   - name: myapp-container
-    image: busybox
+    image: busybox:1.28
     command: ['sh', '-c', 'echo The app is running! && sleep 3600']
 ```
 
@@ -140,14 +140,14 @@ metadata:
 spec:
   containers:
   - name: myapp-container
-    image: busybox
+    image: busybox:1.28
     command: ['sh', '-c', 'echo The app is running! && sleep 3600']
   initContainers:
   - name: init-myservice
-    image: busybox
+    image: busybox:1.28
     command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
   - name: init-mydb
-    image: busybox
+    image: busybox:1.28
     command: ['sh', '-c', 'until nslookup mydb; do echo waiting for mydb; sleep 2; done;']
 ```
 

content/en/docs/tutorials/stateful-application/basic-stateful-set.md

@@ -218,7 +218,7 @@ for i in 0 1; do kubectl exec web-$i -- sh -c 'hostname'; done
 web-0
 web-1
 
-kubectl run -i --tty --image busybox dns-test --restart=Never --rm /bin/sh 
+kubectl run -i --tty --image busybox:1.28 dns-test --restart=Never --rm /bin/sh 
 nslookup web-0.nginx
 Server:    10.0.0.10
 Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local