Apply Rolling Updates

We have our service deployed; now we can update the version of NGINX to version 1.13.

1.    Update the service
               $ docker service update --image nginx:1.13 --detach=true nginx1
 
This triggers a rolling update of the swarm.  to see the updates in real time, quickly enter the following command  over and over
              $ docker service ps nginx1 
 
2.    Check all the images that have been updated to nginx:1.13.
               $ docker service ps nginx1