Kubernetes system records every update for Deployment:

1. We can list all of the revisions with the subcommand rollout:

// check the rollout history
$ kubectl rollout history deployment simple-nginx
deployments "simple-nginx"
REVISION  CHANGE-CAUSE
1         <none>
2         kubectl edit deployment simple-nginx --record=true
3         kubectl set image deployment simple-nginx simple-nginx=nginx:stable --record=true

You will get three revisions, as in the preceding lines, for the Deployment simple-nginx. For Kubernetes Deployment, each revision has a matched ReplicaSet and represents a stage of running an update command. The first revision is the initial state of simple-nginx. Although there is no command tag for indication, Kubernetes takes its creation as its first version. However, you could still record the command when you create the Deployment.

2. Add the flag --record after the subcommand create or run.
3. With the revisions, we can easily resume the change, which means rolling back the update. Use the following commands to rollback to previous revisions:

// let's jump back to initial Deployment!
// with flag --to-revision, we can specify which revision for rollback processing
$ kubectl rollout undo deployment simple-nginx --to-revision=1
deployment.apps "simple-nginx"
// check if the rollback update is finished
$ kubectl rollout status deployment simple-nginx
...                                             
deployment "simple-nginx" successfully rolled out
// take a look at ReplicaSets, you will find that the old ReplicaSet takes charge of the business now
$ kubectl get rs
NAME                      DESIRED   CURRENT   READY     AGE
simple-nginx-585f6cddcd   5         5         5         4h
simple-nginx-694f94f77d   0         0         0         4h
simple-nginx-b549cc75c    0         0         0         3h
// go ahead and check the nginx webpage or the details of Deployment
$ curl $SERVICE_URL
$ kubectl describe deployment simple-nginx

4. Without specifying the revision number, the rollback process will simply jump back to previous version:

// just go back to previous status
$ kubectl rollout undo deployment simple-nginx
deployment.apps "simple-nginx"
// look at the ReplicaSets agin, now the latest one takes the job again
$ kubectl get rs
NAME                      DESIRED   CURRENT   READY     AGE
simple-nginx-585f6cddcd   0         0         0         4h
simple-nginx-694f94f77d   0         0         0         4h
simple-nginx-b549cc75c    5         5         5         4h