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Docker Introduction#

What Is The Docker?#

  • Docker is a container management service. The keywords of Docker are develop, ship and run anywhere. The whole idea of Docker is for developers to easily develop applications, ship them into containers which can then be deployed anywhere.
  • The initial release of Docker was in March 2013 and since then, it has become the buzzword for modern world development, especially in the face of Agile-based projects.
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Docker Components#

  • Docker contains some main components as below
  • Docker for Windows − It allows one to run Docker containers on the Windows OS. We also have docker for Linux and MacOS.
  • Docker Engine − It is used for building Docker images and creating Docker containers. It is the heart of Docker.
  • Docker Hub − This is the registry which is used to host various Docker images.
  • Docker Compose − This is used to define applications using multiple Docker containers.

What Is The Docker Engine?#

  • The Docker engine is an open-source software designed to build and run applications in isolated environments known as containers.
  • It uses OS-level virtualization to run the applications. This is similar to virtual machines but the Docker engine offers a more resource-friendly and portable environment to our processes.
  • Developed by Docker.Inc under the Apache License, the Docker engine hosts images, networks, and containers through a server-side daemon process. Since its initial release in 2013, Docker has grown massively in demand and reputation.

What Is The Docker Container?#

  • A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.
  • Container images (docker images) become containers at runtime and in the case of Docker images become containers when they run on Docker Engine.
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What Is The Docker Images?#

  • A Docker image is a file used to execute code in a Docker container. Docker images act as a set of instructions to build a Docker container, like a template. Docker images also act as the starting point when using Docker. An image is comparable to a snapshot in virtual machine (VM) environments
  • Docker Engine is used to create, run and deploy applications in containers. A Docker image contains application code, libraries, tools, dependencies and other files needed to make an application run. When a user runs an image, it can become one or many instances of a container.
  • More indormation
  • Example of a docker image to run a spring boot project
    #get docker image with openjdk 8 installed from docker hub
    FROM openjdk:8-jdk-alpine

    #expose port 8080 to real machine
    EXPOSE 8080

    #some information for docker image
    LABEL owner="duc"
    LABEL maintainer="minhducnguyen189@gmail.com"
    LABEL description="test image my project"

    #copy the jar file in target folder into docker image
    COPY target/my-project-1.0.0-SNAPSHOT.jar my-project-1.0.0-SNAPSHOT.jar

    #run command java to run jar package when docker image is run
    ENTRYPOINT ["java","-jar","/my-project-1.0.0-SNAPSHOT.jar"]
  • run command docker build . --tag myproject to build a docker image with name myproject
  • run command docker run -it -p8080:8080 myproject to run a docker container with 8080 is mapped out side to real machine.

What Is The Docker Hub?#

  • Docker Hub is a service provided by Docker for finding and sharing container images with your team. It is the world’s largest repository of container images with an array of content sources including container community developers, open source projects and independent software vendors (ISV) building and distributing their code in containers.
  • Users get access to free public repositories for storing and sharing images or can choose a subscription plan for private repositories.
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What Is The Docker-Compose?#

  • Docker Compose is a tool for defining and running multi-container Docker applications. With Docker Compose, you use a YAML file to configure your application’s services. Then, with a single command docker-compose up, you create and start all the services from your configuration.
  • Using Compose is basically a three-step process:
    • Define your app’s environment with a Dockerfile so it can be reproduced anywhere.
    • Define the services that make up your app in docker-compose.yml so they can be run together in an isolated environment.
    • Run docker-compose up and the Docker compose command starts and runs your entire app. You can alternatively run docker-compose up using the docker-compose binary.
  • An docker-compose.yml is like the example below. In this example we can see that we have 2 services, one is the mysql_db_container which is using image mysql:latest from the docker hub. The second one is the adminer_container which is using the image adminer:latest from the docker hub also.

docker-compose.yml
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version: '3.7'
services:
  mysql_db_container:
    image: mysql:latest
    command: --default-authentication-plugin=mysql_native_password
    environment:
    MYSQL_ROOT_PASSWORD: password
    MYSQL_DATABASE: todo
    ports:
    - 3306:3306
    volumes:
    - ./mysql:/var/lib/mysql:rw
  adminer_container:
    image: adminer:latest
    environment:
    ADMINER_DEFAULT_SERVER: mysql_db_container
    ports:
    - 9090:8080
- More information

Install Docker And Docker-Compose#

  • Go to link below to download and install Docker as default:
  • For Window

  • For Linux

  • For Install Docker Compose

  • For Linux
  • For Window, It included in the Docker Desktop so we don't need to install anymore.

See Also#

References#