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Now what if you don't want to set up

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your environment variables in this way.

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You don't want to add them

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to your container specification like this.

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Instead you wanna have your key value pairs

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in a separate file or a separate resource

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and therefore for entity in your cluster.

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Maybe also such that different containers specs

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from different pods

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can utilize the same environment variables.

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This would be a common use case

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and something you can also easily implement with Kubernetes.

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For this, I'll add a new YAML file

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and that will be my environment.yamlfile.

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But the name as always is up to you.

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It doesn't have to be named environment.yaml

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In this file, we will create a so-called ConfigMap.

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For this, we first of all need to set the apiVersion

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to v1 again and set the kind to ConfigMap.

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This is simply another resource,

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another object Kubernetes understands.

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And as the name suggests,

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it creates a map of configurations.

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So a key value pair list basically.

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We can and should give it some metadata.

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For example a name by which we later can then use it.

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We could name this data-store-env

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because we'll store the environment variables

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for storing data in here.

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But ultimately this name is up to you.

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Besides the metadata, we then need to add the data

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which we do wanna set up in this ConfigMap.

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And here we don't do this with a spec but with a data key.

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And below that it's super simple.

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You have a bunch of key value pairs,

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for example, folder and then story,

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because I wanna store that story's string

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in an environment variable

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or in this case, simply a key named folder.

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Now this is a ConfigMap

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and we could have multiple key value pairs here

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if we needed it.

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But here I only need one key value payer.

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But you can have as many as you need

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and you don't have dashes here.

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Instead, these are all simply nested key value pairs

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inside of this data object here

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in this ConfigMap configuration.

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Now we can apply this.

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We can apply this file the environment.yamlfile.

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And this creates this ConfigMap.

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As always with kubectl get configmap.

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You can see all the ConfigMaps you have.

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In this case, one ConfigMap with one piece of data in there.

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Now we wanna utilize this ConfigMap

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to set the environment variables for this container.

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And to do that, the env key here

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supports a special syntax so to say.

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Instead of setting a value

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for your environment variable like this,

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you can also replace value with a value from key.

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You still need the name because you still need

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to define the name of the environment variable

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by which it is exposed in your code.

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So that's still set up here,

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but we now have value from instead of value

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and with value from you now can add

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a nested ConfigMapKeyRef, which stands for a key reference.

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Which allows you to point at a specific ConfigMap

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and there in that map a specific data key,

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which holds the value you wanna set as a value

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for this environment variable in this container.

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For this ConfigMapKeyRef takes another nested object

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where you specified a name of the ConfigMap.

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So in my case, that is this name here, data-store-env,

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and then the key name, which value you wanna set as a value

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for a story folder in this case.

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And in my case to key name is folder.

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So I will set folder here as a key name.

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And this will now pull the value out of the ConfigMap

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and set it as a value for this story folder.

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So now if we run kubectl apply-f=deployment.yaml,

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We apply the updated deployment, which now pulls the value

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for the story folder environment variable

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out of that ConfigMap which we created and applied before.

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Hence with get deployments,

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we see this deployment is up and running,

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and if we run get pods

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we again, see the old pods are being terminated

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and the new pods are getting started.

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And of course we can still work with our application

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and send our requests there as before.

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This all still works because our application didn't change.

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We just changed how we get the name off the folder

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in which our data is stored.

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And as you can see, you can use a ConfigMap

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instead of hard coding to value here If you wanna do that.

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And that's basically for environment variables already.

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With that again, you got full flexibility.

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You can use a file which you create as a ConfigMap

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and apply, and then get the values from there

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or as I showed you before,

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you directly add a value here like this.

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Both together, of course does not work

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you should either set the value here

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in your container specification or point at a ConfigMap

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from which you wanna get the value.

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But with that, we know how to set environment variables.

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And of course before that, we also learned

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how we can work with volumes.

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And that's a lot of important information

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about working with data in Kurbenetes clusters.