This means that these developers will be able to take advantage of WSL 2 and Docker’s integration, allowing developers to store their code within their WSL 2 distro and run the Docker CLI from within this distro. This removes the need to access files stored on the Windows host and provides significant performance improvements for users.

To find out more about using Docker Desktop with WSL 2, check out Simon’s full tips and tricks article. If you want to learn more about how Docker developed the WSL 2 backend you can have a look through our history of the integration or learn more about the implementation details of the backend check out one of Simon’s other blog posts. 

If you are enjoying Docker Desktop but have ideas of what we could do to make it better then please give us feedback. You can let us know what features you want to see next via our roadmap, including voting up GPU support for WSL 2. Or if you are new to Docker, download Docker Desktop and get started with WSL 2 today.

With this announcement, the launch of the Windows 2004 release imminently and Docker Desktop v2.3.02 reaching WSL2 GA , we thought this would be a good time to reflect on how we got to where we are today with WSL 2.

April 2019

Casting our minds back to 2019 (a very different time!), we first discussed WSL 2 with Microsoft in April. We were excited to get started and wanted to find a way to get a build as soon as possible.

May 2019

It turned out the easiest way to do this was to collect a laptop at Kubecon EU (never underestimate the bandwidth of a 747). We brought this back and started work on what would be our first ‘hacky’ version of WSL 2 for Docker Desktop.

June 2019

With some internal demo’s done we decided to announce what we were planning <3

This announcement was a bit like watching a swan on a lake, our blog post was calm and collected, but beneath the water we were kicking madly to take us towards something we could share more widely.

July 2019

We finally got far enough along that we were ready to share something!

And not long after we released our first preview of Docker Desktop using WSL 2

August-September 2019

Once again, with a preview out and things seeming calm we went back to work. We were talking with Microsoft weekly about how we could improve what we had, on fixing bugs and generally on improving the experience. Simon and Ben did have enough time though to head over to the USA to talk to Microsoft about how we were getting on.

October 2019

We released a major rework to how Docker Desktop would integrate with WSL 2:

Along with adding K8s support and providing feature parity with our old Hyper-V based back end. We also made the preview more visible in Docker Desktop and our user numbers started to increase

November 2019 – Feb 2020

This time flew by, we spent a lot of this time chasing down bugs, looking at how we could improve the local experience and also what the best ways of working would be:

March 2020

We had built up a fair bit of confidence in what we had built and finally addressed one of the largest outstanding items we still had in our backlog – we added Windows Home support

This involved us removing the functionality associated with running our old Moby VM in Hyper V and all of the options associated with running Windows containers – as these are not supported on Windows Home. With this we were now able to focus on heading straight to GA…

April 2020

We doubled down how we were getting ready for GA, learning lessons on improving our development practice. We wanted to share how we were preparing and testing WSL 2 ready for the 2.7m people out there running Docker Desktop.

May 2020

We finally reached our GA with Docker Desktop v2.3.02!

Now we are out in the wild, we shared some ideas and best practices to make sure you are getting the best experience out of Docker Desktop when working with WSL 2. 

(And of course for Windows Pro users this still comes with all the same features you know and love including the ability to switch back over to using Windows Containers.)

What’s next?

Next, is that people start to use Docker Desktop with WSL 2! To try out Docker Desktop with WSL 2 today, make sure you are on Windows 2004 or higher and download the latest Docker Desktop to get started.

If you are enjoying  Docker Desktop but have ideas of what we could do to make it better then please give us feedback. You can let us know what features you want to see next via our roadmap, including voting up GPU support for WSL 2. 

The original WSL was an impressive effort to emulate a Linux Kernel on top of Windows, but there are such foundational differences between Windows and Linux that some things were impossible to implement with the same behavior as on native Linux, and this meant that it was impossible to run the Docker Engine and Kubernetes directly inside WSL. Instead, Docker Desktop developed an alternative solution using Hyper-V VMs and LinuxKit to achieve the seamless integration our users expect and love today.

Microsoft has just announced WSL 2 with a major architecture change: instead of using emulation, they are actually providing a real Linux Kernel running inside a lightweight VM. This approach is architecturally very close to what we do with LinuxKit and Hyper-V today, with the additional benefit that it is more lightweight and more tightly integrated with Windows than Docker can provide alone. The Docker daemon runs well on it with great performance, and the time it takes from a cold boot to have dockerd running in WSL 2 is around 2 seconds on our developer machines. We are very excited about this technology, and we are happy to announce that we are working on a new version of Docker Desktop leveraging WSL 2, with a public preview in July. It will make the Docker experience for developing with containers even greater, unlock new capabilities, and because WSL 2 works on Windows 10 Home edition, so will Docker Desktop.

Collaborating with Microsoft

As part of our shared effort to make Docker Desktop the best way to use Docker on Windows, Microsoft gave us early builds of WSL 2 so that we could evaluate the technology, see how it fits with our product, and share feedback about what is missing or broken. We started prototyping different approaches and we are now ready to share a little bit about what is coming in the next few months.

Docker Desktop Future

We will replace the Hyper-V VM we currently use by a WSL 2 integration package. This package will provide the same features as the current Docker Desktop VM: Kubernetes 1-click setup, automatic updates, transparent HTTP proxy configuration, access to the daemon from Windows, transparent bind mounts of Windows files, and more.

This integration package will contain both the server side components required to run Docker and Kubernetes, as well as the CLI tools used to interact with those components within WSL. We will then be able to introduce a new feature with Docker Desktop: Linux workspaces.

Linux Workspaces

When using Docker Desktop today, the VM running the daemon is completely opaque: you can interact with the Docker and Kubernetes API from Windows, but you can’t run anything within the VM except Docker containers or Kubernetes Pods.

With WSL 2 integration, you will still experience the same seamless integration with Windows, but Linux programs running inside WSL will also be able to do the same. This has a huge impact for developers working on projects targeting a Linux environment, or with a build process tailored for Linux. No need for maintaining both Linux and Windows build scripts anymore! As an example, a developer at Docker can now work on the Linux Docker daemon on Windows, using the same set of tools and scripts as a developer on a Linux machine:

A developer working on the Docker Daemon using Docker Desktop technical preview, WSL 2 and VS Code remote

Also, bind mounts from WSL will support inotify events and have nearly identical I/O performance as on a native Linux machine, which will solve one of the major Docker Desktop pain points with I/O-heavy toolchains. NodeJS, PHP and other web development tools will benefit greatly from this feature.

Combined with Visual Studio Code “Remote to WSL”, Docker Desktop Linux workspaces will make it possible to run a full Linux toolchain for building containers on your local machine, from your IDE running on Windows.

Performance

With WSL 2, Microsoft put a huge amount of effort into performance and resource allocations: The VM is setup to use dynamic memory allocation, and can schedule work on all the Host CPUs, while consuming as little (or as much) memory it requires – within the limits of what the host can provide, and in a collaborative manner towards win32 processes running on the host.

Docker Desktop will leverage this to greatly improve its resource consumption. It will use as little or as much CPU and memory as it needs, and CPU/Memory intensive tasks such as building a container will run much faster than today.

In addition, the time to start a WSL 2 distribution and the Docker daemon after a cold start is blazingly fast – within 2s on our development laptops, compared to tens of seconds in the current version of Docker Desktop. This opens the door to battery-life optimizations by deferring the daemon startup to the first API call, and automatically stop the daemon when it is not running any container.

Zero-configuration bind mount support

One of the major issues users have today with Docker Desktop – especially in an enterprise environment – is the reliability of Windows file bind mounts. The current implementation relies on Samba Windows service, which may be deactivated, blocked by enterprise GPOs, blocked by 3rd party firewalls etc. Docker Desktop with WSL 2 will solve this whole category of issues by leveraging WSL features for implementing bind mounts of Windows files. It will provide an “it just works” experience, out of the box.

Technical Preview of Docker Desktop for WSL 2

Thanks to our collaboration with Microsoft, we are already hard at work on implementing our vision. We have written core functionalities to deploy an integration package, run the daemon and expose it to Windows processes, with support for bind mounts and port forwarding.

A technical preview of Docker Desktop for WSL 2 will be available for download in July. It will run side by side with the current version of Docker Desktop, so you can continue to work safely on your existing projects. If you are running the latest Windows Insider build, you will be able to experience this first hand. In the coming months, we will add more features until the WSL 2 architecture is used in Docker Desktop for everyone running a compatible version of Windows.

Docker Captain Trevor Sullivan recently released the Image2Docker tool, an open source project we’re hosting on GitHub. Still in it’s early stages, Image2Docker is a Powershell module that you can point at a virtual hard disk image, scan for common Windows components and suggest a Dockerfile. And to make it even easier, we’re hosting it in the Powershell Gallery to make it easy to install and use.

In Powershell, just type:

Install-Module -Name Image2Docker

And you’ll have access to Get-WindowsArtifacts and ConvertTo-Dockerfile. You can even select which discovery artifacts to search for.

Currently Image2Docker supports VHD, VHDK, and WIM images. If you have a VMDK, Microsoft provides a great conversion tool to convert VMDK images to VHD images.

And as an open source project, lead by a Docker Captain, it’s easy to contribute. We welcome contributions to add more discovery objects and functionality.

More Resources:

• Check out Image2Docker in the Powershell Gallery
• Contribute to Image2Docker

Introducing Image2Docker: A New Tool for Prototyping @Windows VM Conversions by @pcgeek86
Click To Tweet