Ubuntu Server Setup Part 10 - Install Docker and Docker Compose
24 Feb 2022- Part 1 - Logging In
- Part 2 - Securing Login
- Part 3 - Installing a Firewall
- Part 4 - Setup Nginx Web Server
- Part 5 - Install Git, Ruby and Jekyll
- Part 6 - HTTPS With Let’s Encrypt
- Part 7 - Email Forwarding with Postfix
- Part 8 - Sending Email Through Gmail
- Part 9 - Setup a Reverse Proxy with Nginx
It’s likely that you will want to run containers of some kind on your server, for that we’ll be installing and using Docker. This consists of a couple different parts - the Docker Engine itself which runs in the background as a daemon process, the docker CLI commands which allow you to interact with the Engine, and finally docker-compose which is another tool for easily managing multiple containers. On Ubuntu based machines the recommended way of installation is to use the official Docker repository.
Install Prerequisites and Set Up the Repository
Before we do anything more, update your local apt repositories and install a few prerequisite packages which are required in later steps:
$ sudo apt-get update
$ sudo apt-get install ca-certificates curl gnupg
Next, we need to add the official GPG key provided by Docker for their repository:
$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
Finally, we can add the official Docker repository, specifying that the releases must be signed by the GPG key we downloaded in the previous step. The command below will point to the stable repository, but you can use the nightly or test channels if you prefer:
$ 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
Install Docker
Now we have the Docker repository and keys setup, we can pull down the latest packages again and directly install Docker directly through apt:
$ sudo apt-get update
$ sudo apt-get install docker-ce docker-ce-cli containerd.io
If everything completed successfully you should now have Docker Engine running in the background and the ability to run the docker CLI commands to run and manage images/containers. To verify things are working correctly, start an instance of the hello-world image:
$ sudo docker run hello-world
More details at https://docs.docker.com/engine/install/ubuntu/
Configuration Tips
Run Docker CLI as a non-root user
You may have noticed in the verify step above that we had to invoke the docker run command as root in order to successfully run a new container. This is required since the Docker daemon always runs as the root user and it binds to a Unix socket which is also owned by root. This is quite painful when interacting with the CLI however, so there is a workaround using groups:
# add a new group called 'docker' (it might already exist)
$ sudo groupadd docker
# add the current user to the docker group
$ sudo usermod -aG docker $USER
# after logging out and back in again you should be able to run docker without sudo
$ docker run hello-world
Note that this is not the same as running the daemon itself as a non-root user, so all the same security implications still remain when running containers.
Run Docker on startup
By default the daemon processes required to interact with Docker are not configured to start when the system boots. To rectify this we can instruct systemd to automatically start them for us:
$ sudo systemctl enable docker.service
$ sudo systemctl enable containerd.service
More details at https://docs.docker.com/engine/install/linux-postinstall/
Install Docker Compose
For reasons I don’t fully understand docker-compose doesn’t ship with the core Docker packages and so requires an extra installation step. Fortunately, it’s just a single binary so we can just directly download it into a location within the current PATH and start using it:
# download the latest release binary (replace the version from https://github.com/docker/compose/releases)
$ sudo curl -L "https://github.com/docker/compose/releases/download/v2.2.3/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
# add execute permissions
$ sudo chmod +x /usr/local/bin/docker-compose
# verify everything is working
$ docker-compose --version
Docker Compose version v2.2.3
More details at https://github.com/docker/compose