DockerFiles must start with a Docker image as the base. In our case, this base image is a .NET Core 2.0 Docker image developed by Microsoft.
We can see all the images by Microsoft at: https://hub.docker.com/r/microsoft/ aspnetcore-build/.
Our DockerFile must begin with the FROM microsoft/aspnetcore-build line.
If we want, we can build our own Docker image from an operating system baseline, but there are a lot of things we should do before deploying the project to it, such as installing HTTP libraries, SSL libraries, .NET Core Runtime, and so on. We can see layers of a DockerFile of aspnetcore-build:2.0 at https://hub.docker.com/r/microsoft/dotnet/~/dockerfile/.
The second line in the DockerFile is the working directory; in ...
