Docker is an application that simplifies the process of managing application processes in containers. Containers let you run your applications in resource-isolated processes. They’re similar to virtual machines, but containers are more portable, more resource-friendly, and more dependent on the host operating system.
For a detailed introduction to the different components of a Docker container, check out The Docker Ecosystem: An Introduction to Common Components.
In this tutorial, you’ll install and use Docker Community Edition (CE) on Ubuntu 18.04. You’ll install Docker itself, work with containers and images, and push an image to a Docker Repository.
To follow this tutorial, you will need the following:
- One Ubuntu 18.04 server set up by following the Ubuntu 18.04 initial server setup guide, including a sudo non-root user and a firewall.
- An account on Docker Hub if you wish to create your own images and push them to Docker Hub, as shown in Steps 7 and 8.
Step 1 — Installing Docker
The Docker installation package available in the official Ubuntu repository may not be the latest version. To ensure we get the latest version, we’ll install Docker from the official Docker repository. To do that, we’ll add a new package source, add the GPG key from Docker to ensure the downloads are valid, and then install the package.
First, update your existing list of packages:
sudo apt update
Next, install a few prerequisite packages which let
apt use packages over HTTPS:
sudo apt install apt-transport-https ca-certificates curl software-properties-common
Then add the GPG key for the official Docker repository to your system:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Add the Docker repository to APT sources:
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
Next, update the package database with the Docker packages from the newly added repo:
sudo apt update
Make sure you are about to install from the Docker repo instead of the default Ubuntu repo:
apt-cache policy docker-ce
You’ll see output like this, although the version number for Docker may be different:Output of apt-cache policy docker-ce
docker-ce: Installed: (none) Candidate: 18.03.1~ce~3-0~ubuntu Version table: 18.03.1~ce~3-0~ubuntu 500 500 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages
docker-ce is not installed, but the candidate for installation is from the Docker repository for Ubuntu 18.04 (
Finally, install Docker:
sudo apt install docker-ce
Docker should now be installed, the daemon started, and the process enabled to start on boot. Check that it’s running:
sudo systemctl status docker
The output should be similar to the following, showing that the service is active and running:
Output● docker.service - Docker Application Container Engine Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled) Active: active (running) since Thu 2018-07-05 15:08:39 UTC; 2min 55s ago Docs: https://docs.docker.com Main PID: 10096 (dockerd) Tasks: 16 CGroup: /system.slice/docker.service ├─10096 /usr/bin/dockerd -H fd:// └─10113 docker-containerd --config /var/run/docker/containerd/containerd.toml
Installing Docker now gives you not just the Docker service (daemon) but also the
docker command line utility, or the Docker client. We’ll explore how to use the
docker command later in this tutorial.