'Unable to Find User ContainerUser' when building Windows Dockerfile via Actions Runner

Question

When building my windows dockerfile (.net core nano)...

docker build -f *** -t ***:*** --build-arg ARG1=foo --build-arg ARG2=bar .

I'm getting an error during the build that occurs in response to my first RUN command. The command will fail with the following message:

ERROR: failed to solve: process "cmd /S /C dotnet restore \"myproject.csproj\"" did not complete successfully: unable to find user ContainerUser: invalid argument

In my case this is a dotnet restore command but any RUN statement will result in:

unable to find user ContainerUser: invalid argument

Note that the default user for windows nanoserver containers is ContainerUser. If I designate another user eg. USER ContainerAdministrator prior to the RUN statement, the same failure occurs for that user too (unable to find user ContainerAdministrator: invalid argument).

Dockerfile snippet:

FROM mcr.microsoft.com/dotnet/sdk:7.0-nanoserver-1809 AS build
WORKDIR /src
COPY ["myproject.csproj", "myproject/"]
RUN dotnet restore "myproject/myproject.csproj"  <--- Error thrown here (user not found)

The caveat is that this is only occuring when ran from a github actions workflow on a self-hosted windows runner. The Dockerfile builds in other environments no problem and has been deployed successfully. However I don't have access to the runner, so I'm trying to troubleshoot from afar.

Any ideas as to what would cause the user to not be found in the container? I'm having a hard time finding any documentation around this. Thanks

Answer 1

I had the same issue until I removed the nanoserver part of the FROM statement

Try:

FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build

Rather than:

FROM mcr.microsoft.com/dotnet/sdk:7.0-nanoserver-1809 AS build