How to set the entrypoint dll dynamically in Docker image-CodePudding

We want to use a single Dockerfile for a few different projects.

The projects structure is the same and the only different as far as the Dockerfile concerns is the entrypoint dll.

Here is how one of those Dockerfiles looks like:

FROM mcr.microsoft.com/dotnet/runtime:5.0-alpine3.13-amd64

WORKDIR /app
COPY . .

ENTRYPOINT ["dotnet", "dllName.dll"]

I thought about something like that:

FROM mcr.microsoft.com/dotnet/runtime:5.0-alpine3.13-amd64

ARG DLL_NAME

RUN echo "Building for $DLL_NAME"

WORKDIR /app
COPY . .

ENTRYPOINT ["dotnet", $DLL_NAME]

And build it with: --build-arg "DLL_NAME=dllName.dll"
However, the ENTRYPOINT ["dotnet", $DLL_NAME] command doesn't seem to go through when running the image:

/bin/sh: [dotnet,: not found

CodePudding user response：

The RUN instruction expects variables from environment.

Please try changing

FROM mcr.microsoft.com/dotnet/runtime:5.0-alpine3.13-amd64

ARG DLL_NAME

RUN echo "Building for $DLL_NAME"

WORKDIR /app
COPY . .

ENTRYPOINT ["dotnet", $DLL_NAME]

into

FROM mcr.microsoft.com/dotnet/runtime:5.0-alpine3.13-amd64

ARG DLL_NAME
ENV DLL_NAME=$DLL_NAME

RUN echo "Building for $DLL_NAME"

WORKDIR /app
COPY . .

ENTRYPOINT /bin/sh dotnet $DLL_NAME

CodePudding user response：

You can dynamically specify the command to run when you launch a container. This gets appended to the ENTRYPOINT; but, a Dockerfile ENTRYPOINT isn't required. If in your Dockerfile you change ENTRYPOINT to CMD

FROM mcr.microsoft.com/dotnet/runtime:5.0-alpine3.13-amd64
WORKDIR /app
COPY . .
CMD ["dotnet", "dllName.dll"] # <-- not ENTRYPOINT

then when you launch the container you can easily override it, without rebuilding anything

docker run ... my-image \
  dotnet otherDll.dll