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Hi, Let us understand what is config map, how to create, and make use of it.

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Whenever I am creating a pod there will be a requirement to pass some

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configuration informations to the pod how it should function or for the

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containers to give some of the environmental variables that needs

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to be passed and sometimes it may be confidential as well as non-confidential

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informations. For that we do have two type of configuration kinds like

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config maps and secret. Config maps mostly it will be used to store and pass

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the non-confidential informations in the format of key value pair. Whenever I say

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key value pair we can very well relate to the yaml file where the key is going to be

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a string and value could be another map or it could be a collection or even it

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could be another string. Let's go ahead and create a config map and see how to

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make use of it. Once the config map is created the pod can make use of it as

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environmental variables or command line arguments or even a configuration file

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within a volume. Now let us see different options available and this

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configuration map will help to create environmental specific configuration so

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that we can pass it to the container and make the container to have different

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behavior in different environments, in terms of using different images or

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application properties based on the environment. Let us go ahead and create a

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config map I do have a yaml file where I have mentioned the kind as config map

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and within data I do have key value pair for example player initial lives it is 3

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and the value needs to be mentioned as double quotes and that needs to be

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handled as the integer when it is getting read within the application. Within

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config map it has to be of type string or another map. In this case I do have

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game.properties within that I do have two key value pairs where types

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as collection of values and the maximum lives as a string with value 5. So I'm going

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to use this particular yaml file and create a config map, let me go ahead and

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create a config map using the yaml file. I'll use kubectl apply and then the

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yaml file name. So the config map got created let me go ahead and get the

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config maps available, so I do have the config map my config. I'm going to get

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the details about this config map kubectl describe config maps and then the

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name of the config map. The name of the config map was available as a part of the

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yaml file, here I do have the name my-config. So I'm going to give describe

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and then the name of the config map. Here I do have information in terms of

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what are all the keys and the values. Now I'm going to get the output in the

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yaml format which would be much easier to understand kubectl get the

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config maps and the name of the config map -o the yaml format. Here

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the tree structure will be very clearly visible. Now I am going to have a

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property file and use the property file and create the config map. As the

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property files going to have the key value pair, I can use the property file as well so

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I do have a property file with key value pairs. I can directly feed in this property

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file and create a config map. I'll use kubectl create configmap and then name

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of the config file and provide the property file. Now I can get the output

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of the config map that got created as a yaml format. So this different ways of

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creating the configmap will be useful whenever I am going to migrate the

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legacy applications into the kubernetes where I can go ahead and directly use the

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property files or the other yaml files and create a config map. Now let us see how

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to use the config map as a part of the pod and get those values. For the demo

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purpose I am going to create a configmap, let me get the details about the yaml file

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here I do have the configmap where I do have the data that is this is the key and

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this is the value. So I do have special_level as one key special_type as

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another key. Let me go ahead and create a configmap using this specific yaml file

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So I'll use kubectl create and then provide the yaml file the configmap got

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created. Now I'm going to have the yaml file for the pod, let me get the details

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about the pod yaml file. As I mentioned earlier all these yaml files will be added

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as a part of the lecture, so that you can download and directly make use of it.

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Here I'm going to create a pod with the name dapi-test-pod and here I am

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going to pass the config map as the environmental variable. Here this is the

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first time I'm introducing a container can get the environmental variables and

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make use of it internally. So here I'm going to pass the environmental variable

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with the name special_level_key, so what is going to get passed for this particular

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environmental variable that's going to get from the config map and it's going to use

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this specific key special_level and what config map to read from it's going to read

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from special-config configuration map and the same way I'm going to have

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another environmental variable as well that's going to have the name as

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special_type_key within the container I am going to execute the bash shell and

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it is going to echo these two environmental variables. So this pod

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when it is getting created it's going to pass the environment variables by

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reading the config maps and within the container it is going to print this

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environmental variables as a part of the logs and there will not be any daemon it will be

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running, so it's going to log and the life cycle of the pod will get over. I can check

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the logs of the pod and see whether those values got printed or not. Now let

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me go ahead and create the pod, I'm going to use the kubectl create and

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provide the yaml file. Before getting into the pod let's go ahead and check the

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details about the config maps that got created. So I'm going to get the details

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about the special-config that got created using the yaml file and I do have these

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data. That is level 4 and power user as a part of special_level and special_type

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Now I am going to get the details about the pod that got created, let me get the

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list of pods kubectl get pods, so here's where, I do have the pod, let me get the

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description about the pod. The pod got completed these are all the

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environmental variables that was set, now I can get into the pod and see the

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logs. So I can use the command kubectl logs and the name of the pod kubectl

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logs and then name of the pod. So here's where the value that got printed using

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the echo statement. So in a quick summary we have seen what is config

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maps and how to make use of it within the pods and their uses.