前言
.NET Core 2.1将于2021年8月21日结束支持，本来应该没什么影响，该怎么用继续用得了。
但是，如果你在生产环境使用了.NET Core 2.1容器镜像，那就要注意了，从8月21日开始，.NET Core 2.1容器镜像将不再在Docker Hub中提供:
迁移方案
如果你依赖Docker Hub上的.NET Core 2.1容器镜像，可以切换到使用MCR。
比如原来使用的microsoft/dotnet:2.1-aspnetcore-runtime，需要改用mcr.microsoft.com/dotnet/aspnet:2.1:
FROM mcr.microsoft.com/dotnet/aspnet:2.1WORKDIR /app
COPY . .
EXPOSE 80
ENTRYPOINT ["dotnet", "WebApplication1.dll"]
下面是详细的容器镜像迁移列表：
SDK
microsoft/dotnet:2.1-sdk -> mcr.microsoft.com/dotnet/sdk:2.1
microsoft/dotnet:2-sdk -> mcr.microsoft.com/dotnet/sdk:2.1
microsoft/dotnet:2.1-sdk-stretch -> mcr.microsoft.com/dotnet/sdk:2.1-stretch
microsoft/dotnet:2.1-sdk-stretch-arm32v7 -> mcr.microsoft.com/dotnet/sdk:2.1-stretch-arm32v7
microsoft/dotnet:2.1-sdk-nanoserver-1809 -> mcr.microsoft.com/dotnet/sdk:2.1-nanoserver-1809
microsoft/dotnet:2.1-sdk-alpine -> mcr.microsoft.com/dotnet/sdk:2.1-alpine
microsoft/dotnet:2.1-sdk-bionic -> mcr.microsoft.com/dotnet/sdk:2.1-bionic
microsoft/dotnet:2.1-sdk-bionic-arm32v7 -> mcr.microsoft.com/dotnet/sdk:2.1-bionic-arm32v7
microsoft/dotnet:latest -> mcr.microsoft.com/dotnet/sdk:2.1
aspnetcore runtime
microsoft/dotnet:2.1-aspnetcore-runtime -> mcr.microsoft.com/dotnet/aspnet:2.1
microsoft/dotnet:2-aspnetcore-runtime-> mcr.microsoft.com/dotnet/aspnet:2.1
microsoft/dotnet:2.1-aspnetcore-runtime-stretch-slim -> mcr.microsoft.com/dotnet/aspnet:2.1-stretch-slim
microsoft/dotnet:2.1-aspnetcore-runtime-stretch-slim-arm32v7 -> mcr.microsoft.com/dotnet/aspnet:2.1-stretch-slim-arm32v7
microsoft/dotnet:2.1-aspnetcore-runtime-nanoserver-1809 -> mcr.microsoft.com/dotnet/aspnet:2.1-nanoserver-1809
microsoft/dotnet:2.1-aspnetcore-runtime-alpine -> mcr.microsoft.com/dotnet/aspnet:2.1-alpine
microsoft/dotnet:2.1-aspnetcore-runtime-bionic -> mcr.microsoft.com/dotnet/aspnet:2.1-bionic
microsoft/dotnet:2.1-aspnetcore-runtime-bionic-arm32v7 -> mcr.microsoft.com/dotnet/aspnet:2.1-bionic-arm32v7
microsoft/dotnet:aspnetcore-runtime-> mcr.microsoft.com/dotnet/aspnet:2.1
runtime
microsoft/dotnet:2.1-runtime -> mcr.microsoft.com/dotnet/runtime:2.1
microsoft/dotnet:2-runtime -> mcr.microsoft.com/dotnet/runtime:2.1
microsoft/dotnet:2.1-runtime-stretch-slim -> mcr.microsoft.com/dotnet/runtime:2.1-stretch-slim
microsoft/dotnet:2.1-runtime-stretch-slim-arm32v7 -> mcr.microsoft.com/dotnet/runtime:2.1-stretch-slim-arm32v7
microsoft/dotnet:2.1-runtime-nanoserver-1809 -> mcr.microsoft.com/dotnet/runtime:2.1-nanoserver-1809
microsoft/dotnet:2.1-runtime-alpine -> mcr.microsoft.com/dotnet/runtime:2.1-alpine
microsoft/dotnet:2.1-runtime-bionic -> mcr.microsoft.com/dotnet/runtime:2.1-bionic
microsoft/dotnet:2.1-runtime-bionic-arm32v7 -> mcr.microsoft.com/dotnet/runtime:2.1-bionic-arm32v7
microsoft/dotnet:runtime -> mcr.microsoft.com/dotnet/runtime:2.1
runtime-deps
microsoft/dotnet:2.1-runtime-deps -> mcr.microsoft.com/dotnet/runtime-deps:2.1
microsoft/dotnet:2.1-runtime-deps-stretch-slim -> mcr.microsoft.com/dotnet/runtime-deps:2.1-stretch-slim
microsoft/dotnet:2.1-runtime-deps-stretch-slim-arm32v7 -> mcr.microsoft.com/dotnet/runtime-deps:2.1-stretch-slim-arm32v7
microsoft/dotnet:2.1-runtime-deps-alpine -> mcr.microsoft.com/dotnet/runtime-deps:2.1-alpine
microsoft/dotnet:2.1-runtime-deps-bionic -> mcr.microsoft.com/dotnet/runtime-deps:2.1-bionic
microsoft/dotnet:2.1-runtime-deps-bionic-arm32v7 -> mcr.microsoft.com/dotnet/runtime-deps:2.1-bionic-arm32v7
microsoft/dotnet:runtime-deps -> mcr.microsoft.com/dotnet/runtime-deps:2.1
结论
微软还算良心，提供了替代的微软容器注册中心。
如果你准备使用了.NET Core容器镜像，建议从一开始就从mcr.microsoft.com拉取。
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