Installing the Docker client on Windows Subsystem for Linux (Ubuntu)

Oct 20, 2017 · 4 min read

I’m a PC guy, I have always been. I played around a little bit with Linux back in the university days, but that was it.

But now, Windows brought Linux a little closer. I don’t have to do anything complicated like dual booting or having another computer set up just to experience the Linux (non-GUI) environment.

As a Windows Insider, I tried the Windows Subsystem for Linux since day 1 and I really enjoyed it.

Now that Falls Creators U p date is out, I’m using the Ubuntu distro from the store, and the first thing I want to do is having the Docker client installed. It is not rocket science, but I did have some bumps on the road (because of my pretty low knowledge of Linux), so I thought I’d write what I’ve done to achieve that, in case it could be useful to somebody else.

There’s something you need to understand first. The Docker Engine does not run on WSL, you HAVE to have Docker For Windows installed on your host machine. What we’ll end up with at the end of this document is the Docker client running on Linux (WSL) sending commands to your Docker Engine daemon installed on Windows.

So, open you Ubuntu bash console, the first thing is to install the client. In order to do that you have to use apt-get, which is Ubuntu’s package manager (more info about apt here).

1. Update the apt package index:

2. Install packages to allow apt to use a repository over HTTPS:

3. Add Docker’s official GPG key:

Verify that you now have the key with the fingerprint 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88, by searching for the last 8 characters of the fingerprint.

pub 4096R/0EBFCD88 2017–02–22
Key fingerprint = 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88
uid Docker Release (CE deb)
sub 4096R/F273FCD8 2017–02–22

4. Use the following command to set up the stable repository. You always need the stable repository, even if you want to install builds from the edge or test repositories as well. To add the edge or test repository, add the word edge or test (or both) after the word stable in the commands below.

Now we’re ready to install Docker Community Edition

5. Update the apt package index again

6. And install Docker CE

When that finishes, you’ll end up having everything installed in Linux, but as I mentioned before, the Docker Engine does not run in WSL so if you write any command like docker images, you’ll see a message like this one:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

No, it is not running and it’ll never be, at least for now.

You need to tell the Docker client where the Docker host is, and you can do that by using the -H option as follows:

If you don’t want to type the host every time, you can set up and environment variable called DOCKER_HOST to localhost:2375

Now just running docker images will show the images in your host environment.

But, that environment variable will last only as long as the session does. You would have to set it every time you open bash. So, in order to avoid that, you set that variable in a file called .bash_profile in your home directory, like this:

Restart the bash console and the DOCKER_HOST variable should be there, just type docker images to check everything is there.

I hope this post will help other, if it does, let me know.

EDIT: Make sure you expose the daemon on Windows, otherwise it won’t work.

Special thanks to Rich Turner for his kindness and patience.

EDIT: I recently learned there’s an official, more complicated but secure, way of achieving the same, so I thought I’d share it here: WSL Interoperability with Docker

EDIT 2: As of June 12th 2019 WSL 2, has been released to Windows Insiders in the Fast Ring. WSL 2 is a whole new product, you can read more about it here (WSL 2 is now available Windows Insiders). Keep in mind this post is only valid for what is now known as WSL 1 (the old, first, WSL release).

sebastian gomez

Husband, father of 3, developer, techie, marathoner. Research & Development at @Genexus, creator of @IsIt7373MAX

Get started with Docker remote containers on WSL 2

This step-by-step guide will help you get started developing with remote containers by setting up Docker Desktop for Windows with WSL 2 (Windows Subsystem for Linux, version 2).

Docker Desktop for Windows is available for free and provides a development environment for building, shipping, and running dockerized apps. By enabling the WSL 2 based engine, you can run both Linux and Windows containers in Docker Desktop on the same machine.

Overview of Docker containers

Docker is a tool used to create, deploy, and run applications using containers. Containers enable developers to package an app with all of the parts it needs (libraries, frameworks, dependencies, etc) and ship it all out as one package. Using a container ensures that the app will run the same regardless of any customized settings or previously installed libraries on the computer running it that could differ from the machine that was used to write and test the app’s code. This permits developers to focus on writing code without worrying about the system that code will be run on.

Docker containers are similar to virtual machines, but don’t create an entire virtual operating system. Instead, Docker enables the app to use the same Linux kernel as the system that it’s running on. This allows the app package to only require parts not already on the host computer, reducing the package size and improving performance.

Continuous availability, using Docker containers with tools like Kubernetes, is another reason for the popularity of containers. This enables multiple versions of your app container to be created at different times. Rather than needing to take down an entire system for updates or maintenance, each container (and it’s specific microservices) can be replaced on the fly. You can prepare a new container with all of your updates, set up the container for production, and just point to the new container once it’s ready. You can also archive different versions of your app using containers and keep them running as a safety fallback if needed.

To learn more, checkout the Introduction to Docker containers on Microsoft Learn.

Prerequisites

• Ensure your machine is running Windows 10, updated to version 2004, Build 18362 or higher.
• Enable WSL, install a Linux distribution, and update to WSL 2.
• Download and install the Linux kernel update package.
• Install Visual Studio Code(optional). This will provide the best experience, including the ability to code and debug inside a remote Docker container and connected to your Linux distribution.
• Install Windows Terminal(optional). This will provide the best experience, including the ability to customize and open multiple terminals in the same interface (including Ubuntu, Debian, PowerShell, Azure CLI, or whatever you prefer to use).
• Sign up for a Docker ID at Docker Hub(optional).

WSL can run distributions in both WSL version 1 or WSL 2 mode. You can check this by opening PowerShell and entering: wsl -l -v . Ensure that the your distribution is set to use WSL 2 by entering: wsl —set-version 2 . Replace with the distro name (e.g. Ubuntu 18.04).

In WSL version 1, due to fundamental differences between Windows and Linux, the Docker Engine couldn’t run directly inside WSL, so the Docker team developed an alternative solution using Hyper-V VMs and LinuxKit. However, since WSL 2 now runs on a Linux kernel with full system call capacity, Docker can fully run in WSL 2. This means that Linux containers can run natively without emulation, resulting in better performance and interoperability between your Windows and Linux tools.

Install Docker Desktop

With the WSL 2 backend supported in Docker Desktop for Windows, you can work in a Linux-based development environment and build Linux-based containers, while using Visual Studio Code for code editing and debugging, and running your container in the Microsoft Edge browser on Windows.

To install Docker (after already installing WSL 2):

Download Docker Desktop and follow the installation instructions.

Once installed, start Docker Desktop from the Windows Start menu, then select the Docker icon from the hidden icons menu of your taskbar. Right-click the icon to display the Docker commands menu and select «Settings».

Ensure that «Use the WSL 2 based engine» is checked in Settings > General.

Select from your installed WSL 2 distributions which you want to enable Docker integration on by going to: Settings > Resources > WSL Integration.

To confirm that Docker has been installed, open a WSL distribution (e.g. Ubuntu) and display the version and build number by entering: docker —version

Test that your installation works correctly by running a simple built-in Docker image using: docker run hello-world

Here are a few helpful Docker commands to know:

• List the commands available in the Docker CLI by entering: docker
• List information for a specific command with: docker —help
• List the docker images on your machine (which is just the hello-world image at this point), with: docker image ls —all
• List the containers on your machine, with: docker container ls —all or docker ps -a (without the -a show all flag, only running containers will be displayed)
• List system-wide information regarding the Docker installation, including statistics and resources (CPU & memory) available to you in the WSL 2 context, with: docker info

Develop in remote containers using VS Code

To get started developing apps using Docker with WSL 2, we recommend using VS Code, along with the Remote-WSL extension and Docker extension.

Install the VS Code Remote-WSL extension. This extension enables you to open your Linux project running on WSL in VS Code (no need to worry about pathing issues, binary compatibility, or other cross-OS challenges).

Install the VS code Remote-Containers extension. This extension enables you to open your project folder or repo inside of a container, taking advantage of Visual Studio Code’s full feature set to do your development work within the container.

Install the VS Code Docker extension. This extension adds the functionality to build, manage, and deploy containerized applications from inside VS Code. (You need the Remote-Container extension to actually use the container as your dev environment.)

Let’s use Docker to create a development container for an existing app project.

For this example, I’ll use the source code from my Hello World tutorial for Django in the Python development environment set up docs. You can skip this step if you prefer to use your own project source code. To download my HelloWorld-Django web app from GitHub, open a WSL terminal (Ubuntu for example) and enter: git clone https://github.com/mattwojo/helloworld-django.git

Always store your code in the same file system that you’re using tools in. This will result in faster file access performance. In this example, we are using a Linux distro (Ubuntu) and want to store our project files on the WSL file system \\wsl\ . Storing project files on the Windows file system would significantly slow things down when using Linux tools in WSL to access those files.

From your WSL terminal, change directories to the source code folder for this project:

Open the project in VS Code running on the local Remote-WSL extension server by entering:

Confirm that you are connected to your WSL Linux distro by checking the green remote indicator in the bottom-left corner of your VS Code instance.

From the VS Code command pallette (Ctrl + Shift + P), enter: Remote-Containers: Open Folder in Container. If this command doesn’t display as you begin to type it, check to ensure that you’ve installed the Remote Container extension linked above.

Select the project folder that you wish to containerize. In my case, this is \\wsl\Ubuntu-20.04\home\mattwojo\repos\helloworld-django\

A list of container definitions will appear, since there is no DevContainer configuration in the project folder (repo) yet. The list of container configuration definitions that appears is filtered based on your project type. For my Django project, I’ll select Python 3.

A new instance of VS Code will open, begin building our new image, and once the build completed, will start our container. You will see that a new .devcontainer folder has appeared with container configuration information inside a Dockerfile and devcontainer.json file.

To confirm that your project is still connected to both WSL and within a container, open the VS Code integrated terminal (Ctrl + Shift +

). Check the operating system by entering: uname and the Python version with: python3 —version . You can see that the uname came back as «Linux», so you are still connected to the WSL 2 engine, and Python version number will be based on the container config that may differ from the Python version installed on your WSL distribution.

To run and debug your app inside of the container using Visual Studio Code, first open the Run menu (Ctrl+Shift+D or select the tab on the far left menu bar). Then select Run and Debug to select a debug configuration and choose the configuration that best suites your project (in my example, this will be «Django»). This will create a launch.json file in the .vscode folder of your project with instructions on how to run your app.

From inside VS Code, select Run > Start debugging (or just press the F5 key). This will open a terminal inside VS Code and you should see a result saying something like: «Starting development server at http://127.0.0.1:8000/ Quit the server with CONTROL-C.» Hold down the Control key and select the address displayed to open your app in your default web browser and see your project running inside of its container.

You have now successfully configured a remote development container using Docker Desktop, powered by the WSL 2 backend, that you can code in, build, run, deploy, or debug using VS Code!

Troubleshooting

WSL docker context deprecated

If you were using an early Tech Preview of Docker for WSL, you may have a Docker context called «wsl» that is now deprecated and no longer used. You can check with the command: docker context ls . You can remove this «wsl» context to avoid errors with the command: docker context rm wsl as you want to use the default context for both Windows and WSL2.

Possible errors you might encounter with this deprecated wsl context include: docker wsl open //./pipe/docker_wsl: The system cannot find the file specified. or error during connect: Get http://%2F%2F.%2Fpipe%2Fdocker_wsl/v1.40/images/json?all=1: open //./pipe/docker_wsl: The system cannot find the file specified.

Trouble finding docker image storage folder

Docker creates two distro folders to store data:

You can find these folders by opening your WSL Linux distribution and entering: explorer.exe . to view the folder in Windows File Explorer. Enter: \\wsl\ \mnt\wsl replacing with the name of your distribution (ie. Ubuntu-20.04) to see these folders.

Find more on locating docker storage locations in WSL, see this issue from the WSL repo or this StackOverlow post.

For more help with general troubleshooting issues in WSL, see the Troubleshooting doc.