Docker - dotnet restore fails connection to private feeds

Question

Calling do.net restore <project> from my Dockerfile is resulting in a NU1301: Unable to load the service index for source error. I've been going through many of the suggested similar questions and continue to have issues. Here is as much info about the things I've tried as I can provide:

• Docker Engine has its DNS set to "8.8.8.8"
• Using Linux containers
• RUN ping google.com succeeds (so I can reach the inte.net)
• Works perfectly fine hitting the nuget.org feed
• The nuget.config file currently has credentials in it just to get this working
  • This will be removed for a different approach once I get this working
  • These are the same credentials (username/PAT) that I use during development on my host machine
• RUN curl <nuget_feed_url> succeeds
• Running the restore command with --verbosity detailed doesn't provide any other error messages but the one

Here is the section of the Dockerfile in question

FROM mcr.microsoft.com/dotnet/aspnet:6.0.13 AS base
# Create dockeruser in base layer
RUN addgroup --system --gid 1000 dockergroup \
    && adduser --system --uid 1000 --ingroup dockergroup --shell /bin/sh dockeruser

WORKDIR /app
EXPOSE 8080

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
# Arguments are required in each stage in order to get the correct value

WORKDIR /src
COPY ["src/Nucleus.LumberYard.API/", "Nucleus.LumberYard.API/"]
COPY ["./nuget.config", "./nuget.config"]

WORKDIR "/src/Nucleus.LumberYard.API"
#COPY [".editorconfig", "./"]
RUN dotnet restore "Nucleus.LumberYard.API.csproj"
RUN dotnet build "Nucleus.LumberYard.API.csproj" -c Release --no-restore

Environment info

• Docker Desktop v3.3.1
• Docker v20.10.5

Answer 1

Based on my understanding you have the following scenario:

• a .NET 6 application with some references to nuget packages
• some nuget packages are taken from the usual Nuget public repository, some others are taken from a private nuget feed
• you are distributing your application via a docker image and during the docker build process you want to run a do.net restore command targeting one of your csproj file
• the do.net restore command fails because the do.net cli is unable to talk with your private nuget feed

I encountered the very same situation with the project I'm working on. We have a private Nuget feed hosted in Azure Devops and we too had some troubles figuring out how to solve this.

First of all, let's clarify the root cause of the problem. You did the right thing veryfying that you are able to reach the nuget feed from your build machine, via the curl command you mentioned. What is actually failing is the authentication between your build machine and the private nuget feed.

The first thing you need is a personal access token with read permissions for your nuget feed. You can follow this guide to create the personal access token you need.

Once you have the token, you need to provide it to the do.net cli. There are several ways to do so, I'm going to explain the one that worked for us.

Instead of adding the nuget source to the nuget.config file, we registers it via a cli command. I'm quite sure there is a way to do exactly the same thing via the nuget.config file (see here for more details).

This is the cli command we use inside of our docker file:

RUN dotnet nuget add source https://foo.bar.com/something/nuget/v3/index.json -u "whatever" -p "my-personal-access-token" --store-password-in-clear-text --valid-authentication-types "basic"

Notice that:

• https://foo.bar.com/something/nuget/v3/index.json is the absolute URL pointing to the index of your private nuget feed
• the username can be whatever you like. You do need to provide a value, but I didn't notice any difference even putting there a random string like whatever
• the fictious value my-personal-access-token must be substituted with the personal access token you have created as a first step

Here you can find the full reference for the do.net nuget add source command.

After registering this source with the do.net cli, you will be able to run your do.net restore command with no errors.

Hope this helps!