Windows docker container linux

Docker Desktop WSL 2 backend

Estimated reading time: 7 minutes

Windows Subsystem for Linux (WSL) 2 introduces a significant architectural change as it is a full Linux kernel built by Microsoft, allowing Linux containers to run natively without emulation. With Docker Desktop running on WSL 2, users can leverage Linux workspaces and avoid having to maintain both Linux and Windows build scripts. In addition, WSL 2 provides improvements to file system sharing, boot time, and allows access to some cool new features for Docker Desktop users.

Docker Desktop uses the dynamic memory allocation feature in WSL 2 to greatly improve the resource consumption. This means, Docker Desktop only uses the required amount of CPU and memory resources it needs, while enabling CPU and memory-intensive tasks such as building a container to run much faster.

Additionally, with WSL 2, the time required to start a Docker daemon after a cold start is significantly faster. It takes less than 10 seconds to start the Docker daemon when compared to almost a minute in the previous version of Docker Desktop.

Prerequisites

Before you install the Docker Desktop WSL 2 backend, you must complete the following steps:

1. Install Windows 10, version 1903 or higher.
2. Enable WSL 2 feature on Windows. For detailed instructions, refer to the Microsoft documentation.
3. Download and install the Linux kernel update package.

Best practices

To get the best out of the file system performance when bind-mounting files, we recommend storing source code and other data that is bind-mounted into Linux containers (i.e., with docker run -v : ) in the Linux file system, rather than the Windows file system. You can also refer to the recommendation from Microsoft.

• Linux containers only receive file change events (“inotify events”) if the original files are stored in the Linux filesystem. For example, some web development workflows rely on inotify events for automatic reloading when files have changed.
• Performance is much higher when files are bind-mounted from the Linux filesystem, rather than remoted from the Windows host. Therefore avoid docker run -v /mnt/c/users:/users (where /mnt/c is mounted from Windows).
• Instead, from a Linux shell use a command like docker run -v

is expanded by the Linux shell to $HOME .

If you have concerns about the size of the docker-desktop-data VHDX, or need to change it, take a look at the WSL tooling built into Windows.

If you have concerns about CPU or memory usage, you can configure limits on the memory, CPU, Swap size allocated to the WSL 2 utility VM.

To avoid any potential conflicts with using WSL 2 on Docker Desktop, you must uninstall any previous versions of Docker Engine and CLI installed directly through Linux distributions before installing Docker Desktop.

Download

Install

Ensure you have completed the steps described in the Prerequisites section before installing the Docker Desktop Stable 2.3.0.2 release.

1. Follow the usual installation instructions to install Docker Desktop. If you are running a supported system, Docker Desktop prompts you to enable WSL 2 during installation. Read the information displayed on the screen and enable WSL 2 to continue.
2. Start Docker Desktop from the Windows Start menu.

From the Docker menu, select Settings > General.

Select the Use WSL 2 based engine check box.

If you have installed Docker Desktop on a system that supports WSL 2, this option will be enabled by default.

Ensure the distribution runs in WSL 2 mode. WSL can run distributions in both v1 or v2 mode.

To check the WSL mode, run:

To upgrade your existing Linux distro to v2, run:

wsl.exe —set-version (distro name) 2

To set v2 as the default version for future installations, run:

wsl.exe —set-default-version 2

When Docker Desktop restarts, go to Settings > Resources > WSL Integration.

The Docker-WSL integration will be enabled on your default WSL distribution. To change your default WSL distro, run wsl —set-default .

For example, to set Ubuntu as your default WSL distro, run wsl —set-default ubuntu .

Optionally, select any additional distributions you would like to enable the Docker-WSL integration on.

The Docker-WSL integration components running in your distro depend on glibc. This can cause issues when running musl-based distros such as Alpine Linux. Alpine users can use the alpine-pkg-glibc package to deploy glibc alongside musl to run the integration.

Click Apply & Restart.

Develop with Docker and WSL 2

The following section describes how to start developing your applications using Docker and WSL 2. We recommend that you have your code in your default Linux distribution for the best development experience using Docker and WSL 2. After you have enabled WSL 2 on Docker Desktop, you can start working with your code inside the Linux distro and ideally with your IDE still in Windows. This workflow can be pretty straightforward if you are using VSCode.

Open VSCode and install the Remote — WSL extension. This extension allows you to work with a remote server in the Linux distro and your IDE client still on Windows.

Now, you can start working in VSCode remotely. To do this, open your terminal and type:

This opens a new VSCode connected remotely to your default Linux distro which you can check in the bottom corner of the screen.

Alternatively, you can type the name of your default Linux distro in your Start menu, open it, and then run code .

When you are in VSCode, you can use the terminal in VSCode to pull your code and start working natively from your Windows machine.

GPU support

Starting with Docker Desktop 3.1.0, Docker Desktop supports WSL 2 GPU Paravirtualization (GPU-PV) on NVIDIA GPUs. To enable WSL 2 GPU Paravirtualization, you need:

• A machine with an NVIDIA GPU
• The latest Windows Insider version from the Dev Preview ring
• Beta drivers from NVIDIA supporting WSL 2 GPU Paravirtualization
• Update WSL 2 Linux kernel to the latest version using wsl —update from an elevated command prompt
• Make sure the WSL 2 backend is enabled in Docker Desktop

To validate that everything works as expected, run the following command to run a short benchmark on your GPU:

Feedback

Your feedback is very important to us. Please let us know your feedback by creating an issue in the Docker Desktop for Windows GitHub repository and adding the WSL 2 label.

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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 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. (Docker Desktop is free for personal use and small businesses, for info on Pro, Team, or Business pricing, see the Docker site FAQs).

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.
• Install WSL and set up a user name and password for your Linux distribution running in WSL 2.
• 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):

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.

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