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By now you saw some examples by Kubernetes

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and letting Kubernetes manage deployments

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for us could be useful.

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Now let me show you how we could actually change our code

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and update our deployment, and then even roll back

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to another of deployment if we wanted to

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because it's really, really easy.

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Let's say we changed our source code here

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and I have more exclamation marks and a new paragraph.

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This is new like this new, like this

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So I changed my source code and I saved that file.

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Now, of course, we need to rebuild our image.

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This doesn't change.

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That's always the case because our code is in the image.

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And if our container somewhere, no matter

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on which machine should be updated

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the image needs to be updated first.

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So I will update my academind/kub-first app image

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with Docker build by rebuilding it

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and using that latest source code.

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And now we want to update our deployment to

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take this new image this updated image into account.

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To update, a deployment, lets first of all,

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check whether the deployment is still there.

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Yes, it is this first step deployment here.

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And to update it

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we can now run the cube control set command

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and we can run it with image to set a new image

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for a specific deployment by targeting deployment slash

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and then the name of your deployment in my case first app.

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So with that

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I'm saying Kubernedes that I want to set a new image

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for a deployment, and after the slash

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the name of the deployment,

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this is the syntax for updating an image.

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But of course

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we now need to let Kuberenetes know what our new image is.

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Of course you could say

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well, we specify that when we created the deployment

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of course, it should always use the same image,

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and whilst this could be a logic you use

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it would also be pretty unflexible.

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If you ever want to switch

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to a different image with a different name

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or a different tech, you couldn't do that.

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That's why now in addition to what you wrote thus far,

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we need to let kubernetes know which current container

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and image to update with which future image.

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So for that we use the current container name, which

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in case you're not sure you can

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find in this web console it's kub-first app.

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So simply the image name we used before.

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So kub first app

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and we set this now equal to the new image we want to use,

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and that would be academind/kub-first app of course.

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Now of course, just like before this will pull the image

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from Docker hub, so first of all,

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we need to push our updated image to Docker hub

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with Docker push.

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So we built the image now we need to push it,

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and once that pushing finished, we can run the command

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I just showed you.

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So it is finished, now execute cube control set image

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deployment/first app old image name=new image,

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this will update the deployment.

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Now, once you executed this command

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if you get your deployments though

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you'll not notice any difference here,

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and if you visit your application

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you'll also not notice any difference here.

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Now, the reason for that is

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that actually new images will only be downloaded

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if they have a different tech.

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Now, there are ways of changing this,

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but it is a good idea to update your tags

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and kind of version your images anyways

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once you are working with a production setup,

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so therefore what do you want to do here

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is when we build our image

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with Docker build command, we want to give it a tag

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and it could simply be an incrementing version number.

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So let's now give it version two, for example.

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So I have column two after my name.

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Now we can push this new image with that tag at the end

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and now this latest image version will be pushed

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to my repository. With that done,

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we can repeat this set image command, to kub control

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set image command, and now specify this tag at the end.

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So column two here, this will now ensure

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that Kubernetes detects that it's a different tag

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and used before, and it will then re download this image

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and restart your containers based on that.

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So now you can see, we get this image updated confirmation.

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You can view the current updating status

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by executing kub control, rollout status deployment/

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and then the name of your deployment in our case first app.

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And you'll see here, it was rolled out successfully.

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And if you go back to your browser and you reload here

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maybe not immediately,

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but after some time you should see the updated output here.

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And if you go to your Kubernetes dashboard here

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and you have a look at your pods

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and you inspect this pod here

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under events, you can see that this new image was polled

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and that a new container was created, based on that image.

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You can also see that

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this is the image we're currently using here.

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So that's how we could now update the image,

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and therefore the source code

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off a container running as part of a pod managed

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by Kubernedes with this kub control set image command.

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Just keep in mind that you need to change your text

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to trigger kubernetes, to re download the image.