DOCKER

       What is Docker?

• It is an open source containerization Platform.
• It is used to automate the deployment of any application.

       What is Container?

• Running instance of an image.
• Containers are deployed applications bundled with all necessary dependencies and configuration files.
• All the elements share the same OS kernel.
• It is an abstraction at the app layer that packages code and dependencies together.
• Multiple containers can run on the same machine and share the OS kernel with other containers, each running as isolated processes in user space.

      What is Virtualization?

• It is an abstract version of a physical machine.
• Hypervisor allows multiple VMs to run on a single machine.
• Each VM includes a full copy of an OS, application and necessary binaries and libraries which takes size in GBs.
• It can be slow to boot.

         Comparison between VM and containers.

    Benefits of Container

• Run Containers in seconds instead of minutes.
• Less resources results less disk space.
• Uses less memory.
• It does not need full OS.
• Deployment and Testing is easy.

  3 Main Docker Components

• Docker Client :- Performs docker build pull and run operations to open up communications with the docker host. The Docker command then employs Docker API to call any queries to run.
• Docker Host:- Contains docker daemon, containers and associated images. The Docker daemon establishes a connection with the registry. The stored images are the type of metadata dedicated to containerized applications.
• Registry:- This is where docker images are stored. There are two of them a public registry and a private one. Docker Hub and Docker cloud are two public registries available for use by anyone.