Running on .NET Alpine docker image

[Lazer91]

I'm struggling to make this work inside an Alpine-based .NET docker image, due to the dependency on glibc. Here's what I tried:

This works (it's Debian)

FROM mcr.microsoft.com/dotnet/aspnet:7.0
COPY bin/Release/net7.0/publish ./app
ENTRYPOINT ["dotnet", "/app/MyApp.dll"]

This doesn't work, glibc is missing in Alpine

FROM mcr.microsoft.com/dotnet/aspnet:7.0-alpine
COPY bin/Release/net7.0/publish ./app
ENTRYPOINT ["dotnet", "/app/MyApp.dll"]

I tried to add gcompact as per THIS but doesn't work (segmentation fault as soon as the lib is invoked in MyApp)

FROM mcr.microsoft.com/dotnet/aspnet:7.0-alpine
RUN apk add --no-cache gcompat libstdc++
COPY bin/Release/net7.0/publish ./app
ENTRYPOINT ["dotnet", "/app/MyApp.dll"]

I tried also sgerrand/alpine-pkg-glibc:

FROM mcr.microsoft.com/dotnet/aspnet:7.0-alpine
RUN wget -q -O /etc/apk/keys/sgerrand.rsa.pub https://alpine-pkgs.sgerrand.com/sgerrand.rsa.pub && \
   wget https://github.com/sgerrand/alpine-pkg-glibc/releases/download/2.35-r1/glibc-2.35-r1.apk  && \
   apk add glibc-2.35-r1.apk
COPY bin/Release/net7.0/publish ./app
ENTRYPOINT ["dotnet", "/app/MyApp.dll"]

but it doesn't work, I get THIS issue.

Has anyone managed to make this work in an Alpine image? I read that it's not recommended to use glibc in Alpine due to the presence of musl.

[timyhac]

Do the libplctag core binaries work by themself for this setup?

[Kyle Hayes]

They might not. You'll probably need to build them using the musl libraries.

[Lazer91]

Indeed we solved by building the native library in an Alpine VM. Here are the commands if anyone is interested:

apk update
apk add build-base gcc git cmake

git clone https://github.com/libplctag/libplctag.git

cd libplctag
mkdir -p build
cd build

cmake .. -DCMAKE_BUILD_TYPE=Release
make

Please note that:

• The output libplctag.so that you will find in the output directory is just a 0 byte symbolic link. You will need to find the file it is pointing to (for example libplctag.so.2.5) and rename it to libplctag.so, then include it in your .NET solution with the "Copy always" action set.
• To avoid the unwanted overwriting of the file at the program startup, the following line of code is required in your app (before any use of the libplctag library), as explained HERE

plctag.ForceExtractLibrary = false;