Question:
I need to run a [Windows] Docker container as an executable, running a rather involved PowerShell script (invoking Java and .NET applications) and exiting. Docker documentation suggests using ENTRYPOINT for this purpose. So I went ahead and created a Dockerfile with the following contents:
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FROM microsoft/dotnet-framework COPY run.ps1 / ENTRYPOINT [ "powershell.exe", "C:\\run.ps1" ] |
The contents of run.ps1 (uber-simplified for this question):
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gci write-host "looks like everything is good!" |
Then, I ran the following commands:
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# Build the Docker image docker build --rm -t testdockerps . # Create/run container using above image docker run -it testdockerps |
The container ran successfully, displaying the contents of C:\ followed by the message – looks like everything is good!.
I have a couple of questions based on what my observations:
- What is the default shell for a Windows based Docker container? Is there any way to set it to PowerShell, so I don’t have to specify “powershell” as the first element of the
ENTRYPOINTJSON array? Should I be using theSHELLcommand in the Dockerfile? - Creating and running the container takes about 3-4 seconds which is somewhat understandable, but after the PS1 script completes, it takes nearly a questionable 10 seconds for the container to exit and return to the command prompt. What may be the cause of this delay?
Answer:
Yes you can specify powershell as default shell like below on top of DOCKERFILE
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SHELL ["powershell", "-Command", "$ErrorActionPreference = 'Stop'; $ProgressPreference = 'Continue'; $verbosePreference='Continue';"] |
I’m not sure you can do anything about the time it takes to spin down your VM