Notes on Windows containers

See: Windows containers overview.

There are two types of Windows containers:

  • Windows Server containers - uses host kernel, similar to Linux docker container. These containers can only run on a host with matching kernel.

  • Hyper-V containers - has own kernel, more like an optimized virtual machine.

Windows containers use Windows API calls, so a Windows host can only support Windows containers.

One way of using these containers is via a Windows implementation of Docker.

See this blog post for more detailed background on Windows containers.

Set up for using containers

To use either type of container on Windows, you will need container host support in your OS. This started with Windows 2016 technical preview 3. You will need:

  • A real or virtual machine with an OS that can support containers, and

  • Container support installed on the OS;

See installing a container host for instructions on setting up a virtual machine with container support, and inplace setup for instructions on installing the container host services into a real or virtual machine running Windows server 2016 tech preview.

I followed the inplace setup instructions on a real machine running server 2016.

Container images

Containers run from OS “images”. If the container corresponds to a running operating system, then the image corresponds to the hard disk of the OS. See Windows container images for instructions on downloading images for use in Windows containers.

Using Windows containers

There are two standard ways to use Windows containers:

Using Windows containers with Docker

Docker gives a nice interface to starting and using Windows containers.

Installing the container host features does not install docker, so, to use Docker, you will need to install Docker.

Then see:

In what follows I’m running in a powershell with admin privileges.

To see a list of images that you have installed:

docker images

On my system, after installing the Container images, I had:

PS C:\WINDOWS\system32> docker images
REPOSITORY              TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
windowsservercore       10.0.10586.0        6801d964fda5        5 months ago        0 B
nanoserver              10.0.10586.0        8572198a60f1        5 months ago        0 B

windowsservercore is an image containing a minimal Windows Server core instance. nanoserver contains a nanoserver instance.

For convenience, you might like to tag the windowsservercore and nanoserver images as being the latest. latest is the default tag that docker uses when selecting a version of the image, so when you ask for windowsservercore, it implies (image name:tag) windowsservercore:latest. If you don’t add these tags, you will need to give the tag explicitly, as in windowservercore:10.0.10586.0. Add the latest tags with:

docker tag windowsservercore:10.0.10586.0 windowsservercore:latest
docker tag nanoserver:10.0.10586.0 nanoserver:latest

You might then get something like this:

PS C:\WINDOWS\system32> docker images
REPOSITORY              TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
windowsservercore       10.0.10586.0        6801d964fda5        5 months ago        0 B
windowsservercore       latest              6801d964fda5        5 months ago        0 B
nanoserver              10.0.10586.0        8572198a60f1        5 months ago        0 B
nanoserver              latest              8572198a60f1        5 months ago        0 B

To play with a Docker container, you might do something like this:

docker run -ti --rm windowsservercore powershell

This will open a new powershell session inside the container. Exit the session to exit the container.

Notice that, if we had not done the docker tag commands above, we would have to give the tag in the docker command, as in docker run -ti --rm windowsservercore:10.0.10586.0 powershell.

If you are on Windows server, and you want to use the nanoserver images, you will need to force docker to use these via Hyper-V containers. This is because nanoserver and Windows server 2016 do not have the same kernel, and Windows server containers need to share a kernel with the host.

To force the creation of Hyper-V containers instead of Windows server containers, use the --isolation=hyperv flag to Docker, as in:

docker run -ti --rm --isolation=hyperv nanoserver cmd

See Docker containers for more detail.

Example of installing into a container

Here I am installing three versions of Python and the MSVC command line tools for Python 2.7 into a container:

docker run -ti --rm -v c:\Users\mb312\Downloads:c:\downloads windowsservercore powershell

Then (in the container):

cd c:/downloads

Where build_container.ps1 is:

# Set environment variable for correct code page on Python 2
[Environment]::SetEnvironmentVariable("PYTHONIOENCODING", "UTF-8", "Machine")
cd c:/downloads
# See:
cmd /c msiexec /qn /i VCForPython27.msi ALLUSERS=1
cmd /c msiexec /qn /i python-2.7.11.amd64.msi TARGETDIR=c:\Python27-x64
cmd /c msiexec /qn /i python-2.7.11.msi
cmd /c msiexec /qn /i python-3.4.4.amd64.msi TARGETDIR=c:\Python34-x64
cmd /c msiexec /qn /i python-3.4.4.msi TARGETDIR=c:\Python34
# See:
cmd /c python-3.5.1-amd64.exe /quiet InstallAllUsers=1 TargetDir=c:\Python35-x64
cmd /c python-3.5.1.exe /quiet InstallAllUsers=1 TargetDir=c:\Python35