Getting Started with Docker: Install Docker Engine

Docker is a set of platform as a service (PaaS) products that use OS-level virtualization to deliver software in packages called containers.

A container is software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, secure, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries, and settings.

The software that hosts the containers is called Docker Engine.

Let’s go through you the steps to install Docker Engine. We’re using the 64-bit version of Ubuntu Impish 21.10. If you encounter problems with older releases, please share in the Comments box below.

1. Uninstall old versions

At the shell type the command:

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

2. Update your system

Enter the command:

$ sudo apt update && sudo apt upgrade

3. Install dependencies

We’ll use apt again to perform this step:

$ sudo apt install apt-transport-https curl

Depending on the version of Ubuntu you’re running you may also need to install ca-certificates and software-properties-common but these packages are already present on Ubuntu 21.10.

4. Add Docker’s GPG key

Add the GPG key for the official Docker repository to your system:

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

5. Add the Docker repository to APT sources

$ 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

6. Update the package database

Update the package database with the Docker packages from the added repository

$ sudo apt update

7. Check we are installing from the Docker repository

Make sure you install from the Docker repository instead of the default Ubuntu repo:

$ apt-cache policy docker-ce

Here’s the output of the command.

sde@ganges:~$ apt-cache policy docker-ce
docker-ce:
  Installed: (none)
  Candidate: 5:20.10.10~3-0~ubuntu-impish
  Version table:
     5:20.10.10~3-0~ubuntu-impish 500
        500 https://download.docker.com/linux/ubuntu impish/stable amd64 Packages

8. Install Docker Engine

Install the latest version of Docker Engine with the command:

$ sudo apt install docker-ce

As the output shows, containerd.io, docker-ce-cli and other packages will also be installed.

sde@ganges:~$ sudo apt install docker-ce
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  containerd.io docker-ce-cli docker-ce-rootless-extras docker-scan-plugin git git-man liberror-perl libslirp0 pigz slirp4netns
Suggested packages:
  aufs-tools cgroupfs-mount | cgroup-lite git-daemon-run | git-daemon-sysvinit git-doc git-email git-gui gitk gitweb git-cvs
  git-mediawiki git-svn
The following NEW packages will be installed
  containerd.io docker-ce docker-ce-cli docker-ce-rootless-extras docker-scan-plugin git git-man liberror-perl libslirp0 pigz
  slirp4netns
0 to upgrade, 11 to newly install, 0 to remove and 0 not to upgrade.
Need to get 99.3 MB of archives.
After this operation, 423 MB of additional disk space will be used.
Do you want to continue? [Y/n]

Docker should now be installed, the daemon started, and the process enabled to start on boot.

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