Demo Setup and Install Docker

In this lesson, you'll learn how to install and get started with Docker—a powerful containerization platform essential for modern application deployment. We'll walk you through setting up Docker on a supported system, using an Ubuntu VM as our example.

Open your browser and navigate to docs.docker.com. Click on the "Get Docker" button to access the Docker Engine Community Edition page, which is the free version featured in this guide.

From the left-hand menu, select your system type. For this demonstration, choose Linux, then select your Ubuntu flavor (such as Disco, Cosmic, Bionic, or Sanyo). Make sure to review the prerequisites confirming that your Ubuntu system is 64-bit and one of the supported versions.

Step 1: Remove Older Docker Versions

Before installing Docker, it is crucial to remove any existing Docker packages. Run the following command:

sudo apt-get remove docker docker.io docker-engine

Since this setup uses Ubuntu Bionic, verify your Ubuntu version by checking the release information:

cat /etc/*release*

Example output:

vagrant@ubuntu-bionic:~$ cat /etc/*release*
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.2 LTS"
NAME="Ubuntu"
VERSION="18.04.2 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.2 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic
vagrant@ubuntu-bionic:~$

Also, remove any older versions to ensure a clean installation:

sudo apt-get remove docker docker-engine docker.io containerd runc

Step 2: Install Docker

There are two primary methods to install Docker: using the package manager or the convenience installation script.

Option 1: Using the Package Manager

1. Update the Repository and Install Prerequisites
   Update your package list and install necessary packages:

   sudo apt-get update
   
   sudo apt-get install \
       apt-transport-https \
       ca-certificates \
       curl \
       gnupg-agent \
       software-properties-common
   

2. Add Docker’s Official GPG Key
   Add the GPG key for Docker:

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

3. Verify the GPG Key Fingerprint
   Run the following command and ensure the output matches:

   sudo apt-key fingerprint 0EBFCD88
   

   GPG Key Verification

   The expected output should look like:

   pub   rsa4096 2017-02-22 [SCEA]
         9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88
   uid           [unknown] Docker Release (CE deb) <[email protected]>
   

Option 2: Using the Convenience Installation Script

If you prefer a simpler method, use Docker's convenience script:

curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh get-docker.sh

After executing the script, you can verify its presence:

ls get-docker.sh

Step 3: Verify Docker Installation

After installation, check Docker’s version to confirm the installation:

sudo docker version

A typical output showing Docker version 19.03.1 might appear as follows:

vagrant@ubuntu-bionic:~$ sudo docker version
Client: Docker Engine - Community
 Version:           19.03.1
 API version:       1.40
 Go version:        go1.12.5
 Git commit:        74ble89
 Built:             Thu Jul 25 21:21:05 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.1
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.5
  Git commit:       74ble89
  Built:            Thu Jul 25 21:19:41 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.2.6
  GitCommit:        894b81a4b802e4eb2a91d1ce216b8817763c29fb
 runc:
  Version:          1.0.0-rc8
  GitCommit:        425e105d5a03fabd737a126ad93d62a9eeede87f
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683
vagrant@ubuntu-bionic:~$

Step 4: Run a Docker Container

To confirm Docker is running correctly, try launching a simple container. Docker Hub offers a variety of images; in this guide, we'll use the fun "whalesay" image.

1. Run the Initial Container Command

   docker run docker/whalesay cowsay boo
   

   Expected output:

     _______
    < boo   >
     -------
            \   ^__^
             \  (oo)\_______
                (__)\       )\/\
                    ||----w |
                    ||     ||
   

2. Modify the Command with Sudo and Change the Message

   sudo docker run docker/whalesay cowsay Hello-World!
   

   When executed, Docker pulls the whale image from Docker Hub and displays a message:

   vagrant@ubuntu-bionic:~$ sudo docker run docker/whalesay cowsay Hello-World!
   Unable to find image 'docker/whalesay:latest' locally
   latest: Pulling from docker/whalesay
   [DEPRECATION NOTICE] registry v2 schema1 support will be removed in an upcoming release. Please contact admins of the docker.io registry NOW to avoid future disruption.
   e190868d6f3f: Pull complete
   909cd34c6fd7: Pull complete
   0b9fbabab7c1: Pull complete
   a3ed95caeb02: Pull complete
   0bf65475aba: Pull complete
   c57b6bcc83e3: Pull complete
   897f867892ef: Pull complete
   8eed3712d2cf: Pull complete
   Digest: sha256:178598e51a26abbc958b8a2e48825c90bc22e641de3d31e18aaf55f3258ba93b
   Status: Downloaded newer image for docker/whalesay:latest
   
     __________
   < Hello-World! >
     ----------
           \   ^__^
            \  (oo)\_______
               (__)\       )\/\
                   ||----w |
                   ||     ||
   vagrant@ubuntu-bionic:~$
   

Conclusion

This demonstration has provided a comprehensive guide to installing Docker on an Ubuntu system, from removing previous installations to launching your first container. With Docker now installed, you can begin exploring containerized application deployments and enjoy the benefits of modern development workflows.

Happy containerizing!