Docker build for C# core need the internet connection

Question

I am writing in C# .NET core (VS 2017), using the build for linux containers, using docker-compose.

When I build the image (or publish), there is always reference to the internet, because of nuget usage.

Last error encountered (which I persume of downtime on the nuget, but no matter - any downtime should not lead to exception in build/publish).

/usr/share/dotnet/sdk/2.1.503/NuGet.targets(114,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. ...

I want to build the image, even the nuget is down, or even there is no interet connection

The yml file look like this:

services:

 myProj:
 image: my_proj
 build:
  context: ./all_projects/base_solution/
  dockerfile: myProj/Dockerfile 

It seems that "dotnet publish..." command call restore from the internet.

If I run publish with --no-restore, the code not compiled, but I want to restore the nuget packages from my own pre-build of my computer.

How can I do it? With no internet connection? Why should I depend on the internet to restore the nuget at each build?

Why cannot I restore nuget package from my own pre-build image, and not always?! get from nuget (actually nuget packages not change occasionally in my code).

May I just copy the folder from the nuget, and not using "COPY" command?

I did the following:

Build an image from a 'common' project, that uses all the nuget package.

Add a reference in the built-image for the new other image, like this:

Create a new common image: # there is no runtime.

FROM microsoft/dotnet:2.1-sdk AS build
WORKDIR /src
COPY TestDock/TestDock.csproj TestDock/

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

And at the original image: FROM microsoft/dotnet:2.1-runtime AS base WORKDIR /app

# FROM microsoft/dotnet:2.1-sdk AS build do:
FROM my_common_image AS build
WORKDIR /src
COPY TestDock/TestDock.csproj TestDock/

# Added the following. I tried to copy all, but this doesn't help.
# I persume I can copy part of the common build.
COPY --from=build /app /app
COPY --from=build /src /src
COPY --from=build /usr /usr

FROM build AS publish
RUN dotnet publish TestDock.csproj --no-restore --no-dependecies -c Release -o /app

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

I have tried to add an intermediate image, with Dockerfile as following:

# This image is base image for all dockers (no need runtime)
#    docker build . -f DockerFile_Common -t docker_common 


FROM microsoft/dotnet:2.1-sdk AS build

COPY . .

WORKDIR /src/myProj

FROM build AS publish

RUN dotnet publish myProj.csproj -c Release -o /app
RUN dotnet pack /src/myProj.csproj -c Release -o /app

and use it in my image (that I don't want to build using the internet), instead of:

FROM microsoft/dotnet:2.1-sdk AS build

I did:

FROM docker_common AS build

I also tried to add the line: "RUN dotnet publish ..." when setting the workdir as the solution folder, and mark the "Microsoft Visual Studio Offline Packages" (unmark default "nuget.org").

Still, the above doesn't build correctly.

Answer 1

For not using the internet, you can follow the steps.

What is needed is to publish in visual studio, as following:

https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/visual-studio-publish-profiles?view=aspnetcore-2.2

(Alternative publish in command line).

dotnet publish myProj.csproj -c Release /p:PublishProfile=Properties\PublishProfiles\ 
   <myprofile>.pubxml /p:PublishDir=<proj_folder>\bin\Release\netcoreapp2.1\publish

or put in the Post-build event a line like:

dotnet publish $(ProjectDir)$(ProjectName).csproj -c $(Configuration) 
/p:PublishProfile=Properties\PublishProfiles\PublishProfile.pubxml 
/p:PublishDir=$(TargetDir)publish --no-build

... and in the Dockerfile I just did with need to do "COPY ..." from the relevant publish directory!

FROM microsoft/dotnet:2.1-runtime

COPY MyProjectFolder/bin/Release/netcoreapp2.1/publish /app
WORKDIR /app

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