What is Docker and how it differs from virtual machine?
Docker is a software tool that helps package and releases other software by creating containers. These containers are like little packages that include everything the software needs to run properly so that it can be easily deployed on different systems. Docker is lighter than traditional methods of packaging software, like Virtual Machines, which makes it faster and more efficient. Many people use Docker to release software, commonly used in Continuous Deployment/Continuous Integration (CD/CI) processes.
Virtual Machines (VMs) create an entire virtualized operating system, with its own resources like memory and storage, on top of a physical machine. This means that VMs are much heavier and require more resources to run than Docker containers.
Docker Images and Containers
Docker images and containers are two key concepts in Docker that help to package and run software applications.
A Docker image is essentially a snapshot of an application and all its dependencies, along with instructions for how to run it. Think of it like a recipe card - it includes all the ingredients and steps needed to make a particular dish. Docker images can be downloaded or shared with others, so they can easily recreate the same application environment on their own machine.
A Docker container, on the other hand, is an instance of a Docker image running as a process on your computer. It's like cooking that dish using the recipe card - you've created a specific version of the application that is running in its own isolated environment. Containers allow you to run multiple instances of an application on the same machine without worrying about conflicts between them or impacting other parts of the system.
Docker Architecture
Docker is a popular platform for containerizing applications. It allows users to create, distribute, and run lightweight containers that contain all the necessary dependencies and configurations needed to run an application.
Docker architecture consists of several components working together:
Docker daemon: This is the core component of Docker that runs on the host machine and manages the containers.
Docker client: The command-line tool used by developers to interact with the Docker daemon.
Docker registry: A repository where Docker images are stored, either publicly or privately. Docker Hub is an example of a public registry.
Docker image: A pre-built package containing all of the dependencies and configurations needed to run an application.
Docker container: A running instance of a Docker image.
When you want to run an application using Docker, you first need to create a Docker image that contains all the necessary dependencies and configurations. You can build your own custom Docker images, or use pre-built images from a registry.
Once you have your Docker image, you can use the Docker client to run it as a container. Docker will create a new container based on the image, and the application will run inside the container in an isolated environment.