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Updating Deployments

Updating the nginx Image #

Let’s see what happens when we set a new image to the Pod. ref

kubectl create \
    -f deploy.yml \
    ngnix = nginx:1.8.0
kubectl get -f deploy.yml

It’ll take a while until the new image is pulled.

Describing the Deployment

Once it’s done, we can describe the Deployment by checking the events it created.

kubectl describe -f deploy.yml

Looking into the Cluster

To be on the safe side, we might want to retrieve all the objects from the cluster.

kubectl get all 

Exploring Ways to Update Deployment

Updating Using Commands

The kubectl set image command is not the only way to update a Deployment. We could also have used as well. The kuectl edit command would be as follows.

The command would be as follows.

kubectl edit -f deploy.yml

Please do NOT execute it. If you do, you’ll need to type :q followed by the enter key to exit.

The above edit command is not a good way to update the definition. It is unpractical and undocumented. The kubectl set image is more useful if we’d like to integrate Deployment updates with one of the CI/CD tools.

Updating the YAML File

Another alternative would be to update the YAML file and execute the kuectl apply command. While that is a good idea for applications that do not update frequently, it does not fit well with those that change weekly, daily, or even hourly.

nginx is one of those that might get updated with a new release only a couple of times a year so having an always up-to-date YAML file in your source code repository is an excellent practice.

Finishing off

We used kubectl set image just as a way to introduce you to what’s coming next when we explore frequent deployments without downtime.

A simple update of Pod images is far from what Deployment offers. To see its real power, we should deploy the API. Since it can be scaled to multiple Pods, it’ll provide us with a much better playground.