How to Install Docker on Ubuntu 20.04

How to Install Docker on Ubuntu 20.04. Docker is a open-source platform that uses OS-level virtualization to deliver software in packages called containers. Container is a unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

Docker container technology was launched in 2013 which jump started a revolution in application development – by democratizing software containers. 

In this guide you are going to learn how to install Docker on Ubuntu 20.04 LTS.

This setup is tested on Google Cloud Platform so it will work fine on any cloud servers or any VPS or any dedicated servers running Ubuntu 20.04.

Prerequisites

1. Running Compute Engine, see the Setting up Compute Engine Instance.

Start by updating the packages to the latest version available.

sudo apt update
sudo apt upgrade

Step 1: Install Docker

Make sure you install the latest version of Docker from the official Docker repository. The official Ubuntu repository also has the Docker installation package, but it may not be the latest version.

Let’s start installing Docker.

Install some packages which allows you to use the packages over HTTPS.

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

Add the GPG key of Docker repository.

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

Now add the Docker repository of Ubuntu 20.04 (|focal) to the apt sources.

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"

Update the packages index and setup your server to install Docker from official Docker repo.

sudo apt update
sudo apt-cache policy docker-ce

You will receive an output similar to this.

Output
docker-ce:
   Installed: (none)
   Candidate: 5:19.03.9~3-0~ubuntu-focal
   Version table:
      5:19.03.9~3-0~ubuntu-focal 500
         500 https://download.docker.com/linux/ubuntu focal/stable amd64 Packages

Now you can install Docker.

sudo apt install docker-ce

Once Docker is installed and the process is enabled to start on boot.

To check the status of Docker you can use the following command.

sudo systemctl status docker

The output will be like this.

Output
● docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2020-05-22 09:18:43 UTC; 29s ago

Configure Sudo permissions for Docker

The docker command can only be executed as root user by default. If you need to run the docker command without sudo, you need to add your username to the docker group.

sudo usermod -aG docker username

Now restart your SSH or open a new terminal to see the changes.

From now you use the docker command without sudo.

Using Docker Commands

To view the system information about Docker.

docker info

Download Docker Images

docker run hello-world

If the output you get is similar to the below then you can access and download images from Docker Hub.

Output
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
0e03bdcc26d7: Pull complete
Digest: sha256:6a65f928fb91fcfbc963f7aa6d57c8eeb426ad9a20c7ee045538ef34847f44f1
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

Run the below command to see downloaded images.

docker images

Docker Commands

Once you have started using Docker you will have many active and inactive containers.

To view all active containers, use the following command.

docker ps

To view all containers which are active and inactive, use the below command.

docker ps -a

To view the latest container

docker ps -l

To start a docker container, use docker start command followed by the Container ID or Container Name.

docker start container-id/name

Likewise to stop a running container you can use the docker stop command followed by Container ID or Container Name.

docker stop container-id/name

If you no longer need the container you can remove the container with the docker rm followed by Container ID or Container Name.

docker rm container-id/name

To enter into interactive shell you can use the following command.

docker run -it container-id/name

You can manually install commands inside the shell.

For more details about docker commands use the docker run help command.

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Conclusion

Now you have learned how to install and manage Docker on Ubuntu 20.04.

Thanks for your time. If you face any problem or any feedback, please leave a comment below.