Switch docker to windows container

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Working in an environment of mixed containers — both Windows and Linux — I wanted to run them all on my dev machine at the same time if possible. I found some instructions from a while ago about this but following them didn’t work.

Turns out some things have changed in the Docker world so here are some updated instructions.

As of this writing, I’m on Docker Desktop for Windows 2.0.0.3 (31259) Community Edition. The instructions here work for that; I can’t guarantee more won’t change between now and whenever you read this.

1. Clean up existing containers before switching to Windows containers. Look to see if you’re using Windows containers. Right-click on the Docker icon in the system tray. If you see “Switch to Windows containers…” then you are not currently using Windows containers. Stop any running containers you have and remove all images. You’ll need to switch to Windows containers and the image storage mechanism will change. You won’t be able to manage the images once you switch.

2. Switch to Windows Containers. Right-click on the Docker icon in the system tray and select “Switch to Windows containers…” If you’re already using Windows containers, great!

3. Enable experimental features. Right-click on the Docker icon in the system tray and select “Settings.” Go to the “Daemon” tab and check the box marked “Experimental features.”

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That’s it! You’re ready to run side-by-side containers.

The big key is to specify --platform as linux or windows when you run a container.

Open up a couple of PowerShell prompts.

In one of them, run docker images just to make sure things are working. The list of images will probably be empty if you had to switch to Windows containers. If you were already on Windows containers, you might see some.

In that same PowerShell window, run:

docker run --rm -it --platform windows microsoft/nanoserver:1803

This is a command-prompt-only version of Windows Server. You should get a C:\> prompt once things have started up.

Leave that there, and in the other PowerShell window, run:

docker run --rm -it --platform linux ubuntu

This will get you to an Ubuntu shell.

See what you have there? Windows and Linux running side by side!

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Type exit in each of these containers to get out of the shell and have the container clean itself up.

Again, the big key is to specify --platform as linux or windows when you run a container.

If you forget to specify the --platform flag, it will default to Windows unless you’ve already downloaded the container image. Once you have used the image, the correct version will be found and used automatically:

# Works because you already used the image once.
docker run --rm -it ubuntu

If you try to run a Linux container you haven’t already used, you may get a message like this:

no matching manifest for windows/amd64 10.0.18362 in the manifest list entries

I’m not sure on the particulars on why sometimes --platform is required and sometimes it’s not. Even after removing all my container images, I was able to run an Ubuntu container without specifying platform, like some cache was updated to indicate which platform should be used by default. YMMV. It doesn’t hurt to include it, however, if you try to use --platform on another machine it may not work — you can only use it when experimental features are enabled.

UPDATE June 14, 2019

I’ve found since working in this mixed environment that there are things that don’t work as one might entirely expect.

• Networking: With Linux-only containers on Windows you get a DockerNAT virtual network switch you can tweak if needed to adjust network connectivity. Under mixed containers, you use the Windows Container network switch, nat and you really can’t do too much with that. I’ve had to reset my network a few times while trying to troubleshoot things like network connections whilst on VPN.
• Building container images that reference files from other images: A standard .NET Core build-in-container situation is to create, in one Dockerfile, two container images — the first builds and publishes the app, the second copies the published app into a clean, minimal image. When in mixed container world, I get a lot of errors like, “COPY failed: file does not exist.” I can look in the intermediate containers and the files are all there, so there’s something about being unable to mount the filesystem from one container to copy into the other container.

Unrelated to mixed containers, it seems I can’t get any container to connect to the internet when I’m on my company’s VPN. VPN seems to be a pretty common problem with Docker on Windows. I haven’t solved that.

It appears there’s still a lot to work out here in mixed container land. You’ve been warned.

This is Chris Gibson’s second post. This post follows on from his first post called: An Introduction to Containers and Docker. You can read all about Chris on our About Us Page

Introduction

So far you have a fresh install of Docker for Windows, which is cool.  However, by default Docker installs a Linux VM to run your containers.  You want to run Windows containers so need to change this.  Luckily Docker makes this easy, but with one potential gotcha.

Locate the Docker icon in the system tray and right click — you will see an option in the menu labelled “Switch to Windows Containers…”

Once you click this, Docker will start the switching process and you will see a “Docker is switching…” message pop up.

After a few moments, Docker will prompt you to enable the Windows Container feature.  Click ok, wait for the install and automated reboot.

When you next log in, Docker will start as normal and you should be all ready to start playing with Windows Containers right? Nope. If you open a PowerShell prompt as Administrator and run the Docker Version command again, you will see that the server “OS/Arch” is still set to “linux/amd64”.  This happens because Docker needs the Container feature installed before it can switch to it.

If you go back to the Docker menu, it will still show the message “Switch to Windows Containers…”.  

Follow the process again and after a while you should get the “Docker is running” pop-up.  To make sure it has switched you can check the Docker Menu — it should look like this:

You can also run the Docker Version command and see the Server “OS/Arch” value, which now shows “windows/amd64”

Now you’re ready to run Windows Containers, which we look at in the next post.

Right-click on the Docker icon in the system tray and select “Switch to Windows containers…” If you’re already using Windows containers, great! Enable experimental features. Right-click on the Docker icon in the system tray and select “Settings.” Go to the “Daemon” tab and check the box marked “Experimental features.”Jun 12, 2019.

You can toggle this by selecting Switch to Linux Containers from the action menu when clicking on the Docker whale icon in the system tray. If you see Switch to Windows Containers , then you are already targeting the Linux daemon. The container should run, print “hello_world”, then exit.

How do I change a Docker container from Linux to Windows?

Switch between Windows and Linux containers From the Docker Desktop menu, you can toggle which daemon (Linux or Windows) the Docker CLI talks to. Select Switch to Windows containers to use Windows containers, or select Switch to Linux containers to use Linux containers (the default).

Can Docker containers run Windows?

Does Docker run on Linux, macOS, and Windows? You can run both Linux and Windows programs and executables in Docker containers. The Docker platform runs natively on Linux (on x86-64, ARM and many other CPU architectures) and on Windows (x86-64).

How do I enable Windows Container feature?

This provider enables the containers feature in Windows and installs the Docker engine and client. Here’s how: Open an elevated PowerShell session and install the Docker-Microsoft PackageManagement Provider from the PowerShell Gallery. If you’re prompted to install the NuGet provider, type Y to install it as well.

Can I have a Linux container on Windows?

One of the most important enhancements is that Docker can now run Linux containers on Windows (LCOW), using Hyper-V technology. Running Docker Linux containers on Windows requires a minimal Linux kernel and userland to host the container processes.

What is Docker Windows container?

Docker is an open-source project for automating the deployment of applications as portable, self-sufficient containers that can run on the cloud or on-premises. Docker is also a company that promotes and evolves this technology, working in collaboration with cloud, Linux, and Windows vendors, including Microsoft.

Is the Docker daemon running Ubuntu Windows?

Is the docker daemon running? No, it is not running and it’ll never be, at least for now. Now just running docker images will show the images in your host environment. Restart the bash console and the DOCKER_HOST variable should be there, just type docker images to check everything is there.

Can I run Ubuntu Docker image on Windows?

It is now possible to run Docker containers on Windows 10 and Windows Server, leveraging Ubuntu as a hosting base. Imagine running your own Linux applications on Windows, using a Linux distribution you are comfortable with: Ubuntu!.

What is Windows Subsystem for Linux in Windows 10?

The Windows Subsystem for Linux (WSL) is a feature of the Windows operating system that enables you to run a Linux file system, along with Linux command-line tools and GUI apps, directly on Windows, alongside your traditional Windows desktop and apps.

What is Kubernetes vs Docker?

A fundamental difference between Kubernetes and Docker is that Kubernetes is meant to run across a cluster while Docker runs on a single node. Kubernetes is more extensive than Docker Swarm and is meant to coordinate clusters of nodes at scale in production in an efficient manner.

Do containers work on Windows?

Container users Containers are portable and versatile, can run apps written in any language, and they’re compatible with any machine running Windows 10, version 1607 or later, or Windows Server 2016 or later.

Is Docker used for deployment?

In simple terms, Docker is a tool that lets developers to create, deploy, and run applications in containers. Containerization is the use of Linux containers to deploy applications. You can build locally, deploy to the cloud, and run anywhere.

How do I enable Hyper-V and containers Windows features in Windows 10?

Enable the Hyper-V role through Settings Right click on the Windows button and select ‘Apps and Features’. Select Programs and Features on the right under related settings. Select Turn Windows Features on or off. Select Hyper-V and click OK.

What is Windows hypervisor platform feature?

Windows Hypervisor Platform – “Enables virtualization software to run on the Windows hypervisor” and at one time was required for Docker on Windows. The Hypervisor platform is an API that third-party developers can use in order to use Hyper-V. Oracle VirtualBox, Docker, and QEMU are examples of these projects.

Can a Docker container run on both Windows and Linux?

With Docker for Windows started and Windows containers selected, you can now run either Windows or Linux Containers simultaneously. The new –platform=linux command line switch is used to pull or start Linux images on Windows. Now start the Linux container and a Windows Server Core container.

Is my Docker container Linux or Windows?

It is worth mentioning, too, that Docker is the only major container platform that is currently compatible with Windows. Other types of container engines, such as OpenVZ and LXD, are still Linux-only, and probably will remain so for the foreseeable future.

Should I use Windows containers instead of Linux containers?

Linux, is a better OS than Windows, its architecture, specially the Kernel and file system is much better than Windows. Containers take advantage of the process isolation in Linux alongside the names spaces to create isolated processes. Until recently you could only use containers in Linux.

Is Docker an OS?

Docker is an open source software platform to create, deploy and manage virtualized application containers on a common operating system (OS), with an ecosystem of allied tools. Docker container technology debuted in 2013; Docker Inc. Mirantis acquired the Docker Enterprise business in November 2019.

Is Docker a VM?

Docker is container based technology and containers are just user space of the operating system. In Docker, the containers running share the host OS kernel. A Virtual Machine, on the other hand, is not based on container technology. They are made up of user space plus kernel space of an operating system.

What can I do with Docker for Windows?

Docker Desktop is an easy-to-install application for your Mac or Windows environment that enables you to build and share containerized applications and microservices. Docker Desktop includes Docker Engine, Docker CLI client, Docker Compose, Docker Content Trust, Kubernetes, and Credential Helper.