In this post i will put down the steps to install docker on Ubuntu 18.04.
Assumptions:
- Installed os version is Ubuntu 18.04
- Configured firewall
- non-root sudo user available
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
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.
Step 2 — Executing the Docker Command Without Sudo (Optional)
By default, the docker command can only be run the root user or by a user in the docker group, which is automatically created during Docker’s installation process. 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:
Output docker: 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, or type the following:
$ su - ${USER}
You will be prompted to enter your user’s password to continue.
Confirm that your user is now added to the docker group by typing:
$ id -nG
The output should now state that you are in the docker group. If you need to add a user to the docker group that you’re not logged in as, declare that username explicitly using:
$ sudo usermod -aG docker username
The rest of this article assumes you are running the docker command as a user in the docker group. If you choose not to, please add sudo in front of the commands.
Let’s explore the docker command next.
Step 3 — Using the Docker Command
Using docker consists of passing it a chain of options and commands followed by arguments. The syntax takes this form:
$ docker [option] [command] [arguments]
To view all available subcommands, type:
$ docker
As of Docker 18, the complete list of available subcommands includes:
Output attach Attach local standard input, output, and error streams to a running container build Build an image from a Dockerfile commit Create a new image from a container's changes cp Copy files/folders between a container and the local filesystem create Create a new container diff Inspect changes to files or directories on a container's filesystem events Get real time events from the server exec Run a command in a running container export Export a container's filesystem as a tar archive history Show the history of an image images List images import Import the contents from a tarball to create a filesystem image info Display system-wide information inspect Return low-level information on Docker objects kill Kill one or more running containers load Load an image from a tar archive or STDIN login Log in to a Docker registry logout Log out from a Docker registry logs Fetch the logs of a container pause Pause all processes within one or more containers port List port mappings or a specific mapping for the container ps List containers pull Pull an image or a repository from a registry push Push an image or a repository to a registry rename Rename a container restart Restart one or more containers rm Remove one or more containers rmi Remove one or more images run Run a command in a new container save Save one or more images to a tar archive (streamed to STDOUT by default) search Search the Docker Hub for images start Start one or more stopped containers stats Display a live stream of container(s) resource usage statistics stop Stop one or more running containers tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE top Display the running processes of a container unpause Unpause all processes within one or more containers update Update configuration of one or more containers version Show the Docker version information wait Block until one or more containers stop, then print their exit codes
To view the options available to a specific command, type:
$ docker docker-subcommand --help
To view system-wide information about Docker, use:
$ docker info
I will explore some of these commands in another blog post. We’ll start by working with images.
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