Kubernetes Architecture

Kubernetes Introduction:

• Till now we have gone through containers and learned about the docker containers, and from this section we will be starting our journey towards K8S.
• . Firstly we will understand the drawbacks of a containerized platform……….
  1. Containers are having many advantages compared to vm and on prim, that’s the main reason many apps

• A Docker image is a file, used to execute code in a container.
• It’s a Read only Template.
• Docker image is created using a Dockerfile.
• A Docker image is made up of Multiple Layers.
• Every Docker Image starts with a Base image.
• The docker run command creates a container from an image.
• The docker commit command creates an image from a container.
• A docker image consists of layer built on top of each other.
• Docker uses Union File System (UFS) to build an image.
• Image is shared across containers.
• Container Image + Writable top layer.
• In docker the version of your application image is referred to as a tag.
• Each layer represents an instruction in the image’s Dockerfile.
• Each layer, except the very last one, is read-only.
• Each layer is only a set of differences from the layer before it
• Containers add a new writable layer on top of the underlying layers.
• All changes made to a running container are made to the Container layer.
• The writable layer is deleted when the container is deleted.
• The image remains unchanged.
• Basic docker Image creation process is
  1. choose a base image
  2. add your installation/configuration steps

• Every container has non-persistent data and this storage gets created with the container, which is the read write layer. l.e., when the container is deleted the data is also inside it gets deleted as its non-persistent.
• Persistent data is the data which we want to store, and this is not ephemeral. We want to stick around, this can be achieved by using docker volumes.
• Volume data lives outside the life of the container.
• Going back to our example, if our application is talking to a database, we want to make sure our data is persistent and therefore live in a volume.
• Non persistent data is commonly referred to as local storage.
• Linux system storage can be found at /var/lib/docker/<name_of_storage>

We will be discussion about 3 types of Volumes:

• Bind Volume
• TempFS
• Docker Volumes

Docker Bind Mount: