Link Docker container to host file system (windows)

Question

i have an web api (dotNetCore 3.1) and im trying to Dockerize it.

Things start to get complicated when I want to write files into my base Host. From what I have read this is probably related to defining a "volume" .

Lets say that i have this part of code:

           using (StreamWriter sr = new StreamWriter(@"C:\program\tmp.txt"))
           {
               while (max == -1 || counter < max)
               {
                   try
                   {
                       sr.WriteLine($"Counter: {++counter}");
                   }
                   catch (Exception)
                   {

                       throw;
                   }
                 
               }

           }

I manage to build a container and run it properly, but an exception was probably thrown out because he does not know the specified Path.

Here is my Dockerfile:

FROM mcr.microsoft.com/dotnet/core/runtime:3.1-nanoserver-1903 AS base
WORKDIR /app

FROM mcr.microsoft.com/dotnet/core/sdk:3.1-nanoserver-1903 AS build
WORKDIR /src
COPY ["dockerTest/dockerTest.csproj", "dockerTest/"]
RUN dotnet restore "dockerTest/dockerTest.csproj"
COPY . .
WORKDIR "/src/dockerTest"
RUN dotnet build "dockerTest.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "dockerTest.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "dockerTest.dll"]

I would be happy if you could help me link the host file system to the container.

Answer 1

When you start docker container using the CLI you'll have to use the option to mount a drive. (you might have to play with the host machine path a bit).

$ docker run -d --name devtest -v C:\data\input.data:/data nginx:latest

Once the container starts you don't have to use host path you can

       using (StreamWriter sr = new StreamWriter(@"/data/input.data"))

This should work for the most part. With little twists.

You should also consider docker compose files that'll save you a lot of typing and passing too many command line parameters.

More info here:

Docker CLI: https://docs.docker.com/storage/volumes/

Docker Compose: https://docs.docker.com/compose/compose-file/#volume-configuration-reference