Adapted from Digital Ocean Guide.
The Docker installation package available in the official Ubuntu 16.04 repository may not be the latest version. To get the latest and greatest version, install Docker from the official Docker repository. This section shows you how to do just that.
First, add the GPG key for the official Docker repository to the 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 $(lsb_release -cs) stable"
Next, update the package database with the Docker packages from the newly added repo:
- sudo apt-get update
Make sure you are about to install from the Docker repo instead of the default Ubuntu 16.04 repo:
- apt-cache policy docker-ce
You should see output similar to the follow:
docker-ce:
Installed: (none)
Candidate: 17.03.1~ce-0~ubuntu-xenial
Version table:
17.03.1~ce-0~ubuntu-xenial 500
500 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
17.03.0~ce-0~ubuntu-xenial 500
500 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
Notice that docker-ce
is not installed, but the candidate for installation is from the Docker repository for Ubuntu 16.04. The docker-ce
version number might be different.
Finally, install Docker:
- sudo apt-get install -y 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 Sun 2016-05-01 06:53:52 CDT; 1 weeks 3 days ago
Docs: https://docs.docker.com
Main PID: 749 (docker)
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.
By default, running the docker
command requires root privileges — that is, you have to prefix the command with sudo
. It can also be run by a user in the docker group, which is automatically created during the installation of Docker. If you attempt to run the docker
command without prefixing it with sudo
or without being in the docker group, you'll get an output like this:
Outputdocker: Cannot connect to the Docker daemon. Is the docker daemon running on this host?.
See 'docker run --help'.
If you want to avoid typing sudo
whenever you run the docker
command, add your username to the docker
group:
- sudo usermod -aG docker ${USER}
To apply the new group membership, log out of the server and back in.