Docker is an open-source platform that allows you to automate the deployment, scaling, and management of applications using containerization. In this guide, we will explore how to install and use Docker on Ubuntu (Linux) operating system.

Prerequisites

Before we begin, make sure you have the following prerequisites:

• An Ubuntu (Linux) operating system
• Root or sudo access

Step 1: Install Docker

To install Docker on Ubuntu, follow these steps:

1. 1. Update the package index:

sudo apt update

1. 1. Install Docker dependencies:

sudo apt install apt-transport-https ca-certificates curl software-properties-common

1. 1. Add the Docker GPG key:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

1. 1. Add the Docker repository:

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

1. 1. Update the package index again:

sudo apt update

1. 1. Install Docker:

sudo apt install docker-ce

1. 1. Start and enable Docker:

sudo systemctl start docker

sudo systemctl enable docker

Step 2: Verify Docker Installation

To verify that Docker is installed correctly, run the following command:

docker --version

You should see the version of Docker installed on your system.

Step 3: Docker Commands

Here are some commonly used Docker commands:

Command	Description
docker pull <image>	Pulls an image from a Docker registry
docker run <image>	Runs a container from an image
docker ps	Lists running containers
docker images	Lists available images
docker stop <container>	Stops a running container
docker rm <container>	Removes a container
docker rmi <image>	Removes an image

Step 4: Dockerfile

A Dockerfile is a text file that contains a set of instructions for building a Docker image. Here’s an example of a simple Dockerfile:

FROM ubuntu:latest
RUN apt update
RUN apt install -y nginx
CMD ["nginx", "-g", "daemon off;"]

To build an image from a Dockerfile, use the following command:

docker build -t <image_name> <path_to_dockerfile>

Once the image is built, you can run a container from it using the docker run command.

Step 5: Docker Compose

Docker Compose is a tool for defining and running multi-container Docker applications. It uses a YAML file to configure the application’s services, networks, and volumes. Here’s an example of a simple Docker Compose file:

version: '3'
services:
  web:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 80:80
    volumes:
      - ./html:/var/www/html
  db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: password

To start the application defined in the Docker Compose file, use the following command:

docker-compose up

This will start the containers defined in the file and attach their output to the console.

Conclusion

In this guide, we have covered the basics of Docker on Ubuntu (Linux). You should now have a good understanding of how to install Docker, use Docker commands, create Docker images using a Dockerfile, and run multi-container applications with Docker Compose. Docker provides a powerful and efficient way to manage your applications and their dependencies, making it an essential tool for modern software development.

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