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Hi let us understand about volumes. Whenever I am starting a pod there may be

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a requirement to store the data within the pod for permanent or for temporary

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purpose and to store the data I need something called a volume. Volume is

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nothing but it's like a virtual hard disk and I need to get the volume resources either

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from the host system or it could be some other NFS like network file system or

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some other storage like block storage available within the cloud environment.

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Let's take this from the simple scenario to the complex scenario for that we need to

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have understanding on the ephemeral storage. While starting a pod there may be

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a requirement to store the data for temporary purpose, let's assume I'm going

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to do some image processing to store the intermediate data, I need this ephemeral

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storage and this is going to share the resources from the underlying host

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system and while creating the pod I can define, how I wanted to have this

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particular ephemeral storage and the scope of this particular storage is

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as long as the scope of the pod is existing that means once the pods life cycle

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gets over the ephemeral storage will also get deleted. So the user should be

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very careful enough not to store any permanent data only the ephemeral data

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or the temporary data can be stored within this ephemeral storage and that is

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called as an empty directory. Let's go ahead and create a pod with

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empty directory and see how it's going to behave I have minikube running within my

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system and I'm going to use a yaml file that's going to have the content like this.

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So I am mentioning kind as pod and within the specification of the pod I am

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going to mention the volume. I am going to give a name I will mention that as

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emptydir, the yaml content gets over over here and this particular volume will be

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mounted over here using the volume mounts within the container, so within the

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container I am having the key volume mounts and I am mentioning against

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which folder this particular emptydir volume will get mounted. Let me go ahead

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and create the pod using this yaml file, I'll use kubectl apply and I will mention the

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file name the pod should get created. So it's going to create the pod this is this

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specific pod, let me go ahead and get the pod and its status. So one pod is up and

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running, let me go ahead and get details about this specific pod. So here's where I

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do have the container that got created, this is the container ID and I'm going to

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use this specific container ID to get into the container ID and check the volumes

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that got created. So here's where the mounts available and it is mounting or it

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is going to share this specific location as a part of the host system. Let me go ahead

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and get the details about the file system using df command. So I'll provide the

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exec command with kubectl and I'll provide the pod name and I'm going to

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execute the command df. That will get me the file system here I do have the file

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system mention/cache and that's going to get mapped to the host file system. So

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that means this particular host file system is mounted against this cache. Now I can

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get into this specific pod and execute the bash shell. So it's going to get into the pod

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So I am into this specific pod into the root directory, here I can check the

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cache directory. I don't have any content so what I'm going to do I am going to create

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a sample text within this specific folder, so I'm adding a text emptydir test and

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echo that into a file empty dir test.txt So I do have a text file within the folder that is

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mounted and that's going to get mounted against the host file system. Let me go

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ahead and get the container ID, let me come out of this particular pod and

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I'm going to execute the kubectl describe and the pod name. Here I do have the

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container ID. I'm going to do the docker inspect command using this specific

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container ID where I will get the details about this specific docker container that

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is running within the pod, docker inspect and then the container ID. Here I'm going

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to have information on the networking and the volumes that is hosted against

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the container that is running. So if you get into the container details here I should be

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having the details on the hard disk or the volumes that got mounted. So here are the

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mounts array available and I'm going to check the mount that is mounted against

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the /cache folder, so here's where the  /cache available and that is having or

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going to map against this specific folder location within the host file system. Let me

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open another terminal, I'm going to get into this specific location and here

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I should have this specific file that got created as a part of the container

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so I do have that text. So what did we do? We created an empty dir and we made

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that to get mapped or mounted against cache folder and that is going to get

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mapped to a host storage and a temporary folder got created and the

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lifespan of this particular cache folder is as long as this particular pod is existing

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and whenever I am adding a content into this cache folder that will be sharing the

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space available within the host file system. If I create a file called f1.txt the

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same will get created within the host file system as well. Let me go ahead and do

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that let me go ahead and create another file within the pod, now I am into the pod

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let me get into the cache folder and create a file called file1.txt with the

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content file one. So I have created a file file1.txt. let me go ahead and list the files

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available within the host file system, yes the same file is available. Now I am going

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to terminate this particular pod and see what's going to happen to this

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specific folder. Let me come out of the pod and I'm going to execute the command

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kubectl delete pod and then the pod name. The pod should get deleted, let me

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check whether the pods got deleted or not? Yes, there is no pods available. Now let

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me list the files available within this specific pods directory. This entire ID and

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the volume should also get deleted. So I'm going to list ed ID is not existing even

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within this particular folder there should not be any files available and the entire folder

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content from this specific path will get deleted. So in a quick summary we had

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seen what is emptydir volume type and how that's going to get mapped against the

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pod. The similar way there are different type of volumes available and the list it

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keeps on growing, these are all the list of volumes available at the time of recording

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and we are going to see another important type that is host path where

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we will be using it more frequently within the pods. So as a part of this particular

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session we saw how to create the empty dir and what are all its scope within the

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pod and how that's going to share the storage within the

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host file system when the emptydir volume is getting created.