Docker is a platform that enables developers to automate the deployment of applications inside lightweight, portable containers. Here's how to install and use Docker on Ubuntu Server 22.04:

Install the necessary packages that allow apt to use repositories over HTTPS:

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

Add Docker’s official GPG key to verify the authenticity of the packages:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | \
sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Add Docker’s official repository to your system’s software repository list:

echo "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] \
https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | \
sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

Update the package index again to include Docker's packages:

sudo apt update

Install Docker Engine and related components:

sudo apt install docker-ce docker-ce-cli containerd.io

Check the status of Docker to ensure it's running:

sudo systemctl status docker

You should see output indicating that Docker is active and running.

To allow your user to run Docker commands without sudo, add your user to the Docker group:

sudo usermod -aG docker $USER

Apply the group membership changes:

newgrp docker

Now, you can run Docker commands without sudo.

Run a test container to verify that Docker is working correctly:

docker run hello-world

If Docker is installed correctly, you should see a message saying “Hello from Docker!”

Docker Compose is a tool that allows you to define and manage multi-container Docker applications. Here's how to install and use Docker Compose on Ubuntu 22.04:

Docker Compose is now included as a plugin in Docker Engine. To install it:

sudo apt install docker-compose-plugin

Check the version of Docker Compose to ensure it's installed correctly:

docker compose version

You should see output indicating the version of Docker Compose installed.

To define and run multi-container applications:

1. Create a project directory:

mkdir ~/myapp
cd ~/myapp

1. Create a docker-compose.yml file:

vim docker-compose.yml

Add the following content to define a simple web application with Nginx:

snippet.yaml

version: '3.8'
services:
  web:
    image: nginx:latest
    ports:
      - "8080:80"

1. Start the application:

docker compose up -d

The -d flag runs the containers in detached mode.

1. Verify the running containers:

   docker ps

You should see the Nginx container listed.

1. Access the application:

Open a web browser and navigate to http://localhost:8080. You should see the Nginx welcome page.

Docker Compose provides several commands to manage your applications:

• Stop the Application:

docker compose down

This stops and removes all containers defined in the docker-compose.yml file.

• View Logs:

docker compose logs

This displays the logs of all containers. You can specify a service to view logs for a specific container:

docker compose logs web

• Scale Services:

  docker compose up -d --scale web=3

This scales the web service to 3 instances.

• View Service Status:

docker compose ps

This lists the status of all services defined in the docker-compose.yml file.