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‫You've heard me say before in this part of

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‫the course about Kubernetes that it's rather unopinionated.

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‫Which means it gives us a set of tools and commands,

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‫but it doesn't really prescribe one way to do things.

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‫I guess the more ways you could do something, the more

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‫you might say it's unopinionated because you can just

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‫choose whichever path you'd like.

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‫We've talked about, in the previous section, about

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‫three major ways to do

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‫Kubernetes or to manage your Kubernetes workloads,

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‫right. The third one, the declarative, the fully

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‫declarative way, is the one that I want this

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‫whole section to be about.

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‫Which means we're going to be mostly focusing on YAML

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‫and how that works in Kubernetes.

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‫The reason I want this whole section to be about

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‫the declarative way is because it's more of

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‫the DevOps style.

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‫It's more conducive to the infrastructure as

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‫code, and the new term on the block, git-ops, which

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‫is all about storing your YAML and configurations

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‫in git repositories and using git-commits to change

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‫your infrastructure. I don't get too much into git-ops

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‫here but really it's just about applying the automation

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‫style of DevOps to your configurations.

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‫What better way to do that in Kubernetes by using

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‫YAML. The nice thing is there's very few commands you

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‫have got to learn here. Really, all the focus is going to

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‫be learning the different YAML formats.

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‫Here, we're using the kubectl apply command with

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‫a -f to tell it here's the file I want to give

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‫you, and that's the command.

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‫That's the command you use to create something.

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‫That's the command you use to update something, or to edit

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‫a configuration, or to change the image, or whatever you

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‫want to do. That's the same command.

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‫In that way, it's very much like stack deploy in Swarm

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‫where you're just constantly giving it the same command

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‫with updated YAML.

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‫For this section, we're going to skip that middle

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‫type of deployment which has the kubectl create,

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‫and the edit, and the replace, and those commands

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‫because they're not really a good way to

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‫manage production infrastructure anymore.

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‫They don't have a good solid DevOps structure to

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‫them, and this course is all about DevOp style containers.

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‫That's why we want to strive to.

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‫So, do realize, as a disclaimer in this slide, that surely

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‫you can use those commands if you want, but that's not

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‫really the primary way I think you should be using

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‫Kubernetes.

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‫Just because this is the way I recommend it doesn't mean

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‫that there isn't a lot of other possibilities out there.

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‫Let me just throw you some quick examples of different ways

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‫you can use the apply command.

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‫You've seen that we can just tell it a YAML file

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‫and it will apply something that's in there.

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‫Maybe it's a deployment. Maybe it's just a pod.

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‫Maybe it's a service, or a job, or

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‫a cron job, or some other resource.

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‫That -f will work on a whole directory so

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‫you could have a bunch of different objects, or resources,

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‫sort of spread out in different files, maybe one file

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‫per resource. You could put all those in a directory.

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‫You could just point it to that directory and it would

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‫bring in all of those.

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‫Of course, one YAML file can have multiple resources

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‫in it, and I'll show you how that looks in a minute.

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‫Another interesting option here is kubectl apply

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‫with a URL.

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‫We give it that -f, but the file is technically

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‫a URL there. The way it knows that is through the HTTP

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‫protocol. In my case, I've created a

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‫domain that has a couple of examples.

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‫There is a pod.yaml file there and so technically

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‫if you ran that command, it would work.

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‫It would deploy a single pod.

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‫Just be careful of these files because you know it's one

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‫thing to pull something down over the Internet and download

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‫it. It's a whole other thing to one line run

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‫a YAML file in Kubernetes. This is kind of the equivalent

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‫of cURLing something into shell

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‫and thus allowing it to run on your system without even

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‫looking at the file, right. You really don't want to do

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‫that. We don't want to be randomly running stuff and that's

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‫kind of what Kubernetes does, right.

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‫It runs stuff. You might want to cURL that if you have cURL

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‫locally. If you're on a Windows PowerShell, then

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‫you can use that command to open it up in your browser.

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‫In the next lecture, let's start looking at YAML

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‫formatting and how we're going to create these objects.