Using #Docker VOLUME to Remove Installation Files in #WindowsContainer

When working with Windows containers and volumes, you notice that volumes work differently compared to Docker on Linux. For example, you cannot mount to a non-empty directory. More irritating is the fact that you cannot create a volume on a non-empty directory when working on a Dockerfile. By changing around the instructions, you can use volumes to clean up installation files.

As mentioned above, creating a volume on a non-empty directory fails. But when moving the instructions around, you end up with a directory which looses its contents as soon as an instruction ends. This is very useful for building images and getting rid of installation sources.

The folloowing instruction demonstrate this:

# escape=`
FROM microsoft/windowsservercore

SHELL ["powershell", "-Command"]

ENV GIT_VERSION "2.10.2"
ENV GIT_FILE "Git-${GIT_VERSION}-64-bit.exe"
ENV GIT_BASE_URL "https://github.com/git-for-windows/git/releases/download"
ENV GIT_URL "${GIT_BASE_URL}/v${GIT_VERSION}.windows.1/${GIT_FILE}"

VOLUME c:\install
WORKDIR c:\install
RUN Invoke-WebRequest `
        -UseBasicParsing `
        -Uri $Env:GIT_URL `
        -OutFile $Env:GIT_FILE; `

    Start-Process `
        -Wait `
        -Passthru `
        -FilePath $Env:GIT_FILE `
        -ArgumentList '/VERYSILENT /NORESTART /NOCANCEL /SP- /SUPPRESSMSGBOXES'

When creating the volumes first, all following instructions can add to this volume but it is cleared up as soon as the instruction ends. Therefore, the commands called in the RUN instruction download and install git. But instead of removing the file, it gets automatically cleaned up at the end of the RUN instruction.