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Docker is an open platform for developing, building and running containerised applications. It uses OS-level virtualization to deliver and run packages in a loosely isolated environment called containers.

As a developer, you first build the docker image for your application by writing a text document called Dockerfile and the application is then deployed as a container on the Docker host.

So to build the image and deploy the application as a container, you would need Docker on the server on which you are going to run the application. In this post we are going to look at all the steps required to install Docker on Ubuntu.

Prerequisites

• Ubuntu 18.04 and above
• root or sudo access to the server on which you are going to install Docker
• Basic knowledge on Linux commands and terminal window
• An account with Docker Hub if you wish to push your images to Docker Hub

Install Docker on Ubuntu

There are many options to install Docker on Ubuntu but we will look at below two options which are widely used.

Option 1 – Install Docker by using Ubuntu System Repo

sudo apt update

Update system apt package index

sudo apt install docker.io

Install Docker

sudo docker --version

verify the docker installation by checking the version and the output should show something similar to below.

rajesh@ubuntu:~$ sudo docker version
Client:
 Version:           20.10.7
 API version:       1.41
 Go version:        go1.13.8
 Git commit:        20.10.7-0ubuntu5~20.04.2
 Built:             Mon Nov  1 00:34:17 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server:
 Engine:
  Version:          20.10.7
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.13.8
  Git commit:       20.10.7-0ubuntu5~20.04.2
  Built:            Fri Oct 22 00:45:53 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.5.5-0ubuntu3~20.04.2
  GitCommit:        
 runc:
  Version:          1.0.1-0ubuntu2~20.04.1
  GitCommit:        
 docker-init:
  Version:          0.19.0
  GitCommit:        

Option 2 – Install Docker by using Official Docker Repo

sudo apt update

Update system apt package index

sudo apt install ca-certificates curl gnupg lsb-release

Install above few packages which allows apt to communicate with repository over HTTPS

echo  "deb [arch=$(dpkg --print-architecture) 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

Use above command to set the stable version of Docker that we are going to install.

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

Update the system apt package index again and run the Docker install command.

sudo docker --version

Verify the Docker installation by checking the version. You should be seeing output similar to below.

rajesh@ubuntu:~$ sudo docker version
Client: Docker Engine - Community
 Version:           20.10.13
 API version:       1.41
 Go version:        go1.16.15
 Git commit:        a224086
 Built:             Thu Mar 10 14:07:51 2022
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.13
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.15
  Git commit:       906f57f
  Built:            Thu Mar 10 14:05:44 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.5.10
  GitCommit:        2a1d4dbdb2a1030dc5b01e96fb110a9d9f150ecc
 runc:
  Version:          1.0.3
  GitCommit:        v1.0.3-0-gf46b6ba
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Running Docker Commands without root or sudo

We can only run the docker commands from root or sudo or by the users who are part of docker group.

sudo usermod -aG docker <username>

Add the user to the docker group if you want to avoid using root or sudo. You will need to restart the machine for this to take effect.

Running Docker Container

docker run hello-world

Run the above command to create your first hello-world container. This will show “Hello from Docker!” along with other information.

Here are the steps Docker took to display this message:

1. The Docker client contacted the Docker daemon to create a container.
2. The Docker daemon pulled the given “hello-world” image from the Docker Hub repository.
3. The Docker daemon created a new container from that image that produces the above output.
4. The Docker daemon then streamed that output to the Docker client, which sent it
   to your terminal.

Conclusion

In this tutorial, you have learned how to install Docker on Ubuntu and created a sample docker container. It is time for you to go in depth and try all the features which Docker offers.