Docker cheat sheet for .NET Core

This is just a cheat sheet of commands and terminology for Docker and ASP.NET Core; it contains commands that you can find in the original cheat sheet, plus a Dockerfile for ASP.NET Core and a quick guide on how to created one from Visual Studio. Hopefully, both developers that are in the process of getting into the containerize world with Docker and developers that are already in but need a quick recap will find it useful.

Basic terminology

Term Short explanation
Docker Docker is a set of platform as a service products that uses OS-level virtualization to deliver software in packages called containers. Download Docker for Windows here.
Image An image, or more correct, a Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.
Container A container image becomes a container at runtime when they run on Docker Engine
Docker Engine Docker Engine is a container runtime that runs on various Linux (CentOS, Debian, Fedora, Oracle Linux, RHEL, SUSE, and Ubuntu) and Windows Server operating systems…
Docker Hub Docker Hub is a service provided by Docker for finding and sharing container images with your team.
Dockerfile A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

Read more information about Docker Container Images and Docker Containers here.

Basic commands

Follows, a list of basic commands that you will regularly need. Run them using command line from the root of your application – where the Dockerfile should exists.

Term Short explanation
docker pull Retrieve an image from a registry. If you specify only the repository name, Docker will download the image tagged latest from that repository on Docker Hub.
e.g. docker pull mcr.microsoft.com/dotnet/core/aspnet:3.1 pulls the 3.1 runtime, where docker pull mcr.microsoft.com/dotnet/core/sdk pulls the latest .NET Core SDK.
docker build Create a new image by running a Dockerfile. User the -t flag to specify the name of the new image and don’t forget the . (build context for the source files for the COPY command)
e.g. docker build -t image.name.for.my.app:v1 .
docker image list After pulling an image, view the images in your local registry with the docker image list command.
docker ps View active containers. Use the -a flag to view all.
e.g. docker ps -a
docker run Run an image – it will become a container. Specify the option -p for port mapping (left hand side local port, right hand side port exposed by docker) and -d to run it as a background service.
Speficy the --name option to set the name of the container.
e.g. docker run -p 8080:80 -d --name container.name image.name.for.my.app
docker stop Stop an active container by specifying the container ID. Get that with the docker ps command
e.g. docker stop elegant_ramanujan
docker start Restart a stopped container.
e.g. docker start elegant_ramanujan
docker container rm Remove a stopped container. Add the -f flag to force remove a running container (not a graceful shutdown)
e.g. docker container rm -f elegant_ramanujan
docker image rm Remove an image. There is no force flag here, all containers using this image must be stopped.
e.g. docker image rm mcr.microsoft.com/dotnet/core/samples:aspnetapp

A Dockerfile sample

Living in the root of the application, a Dockerfile is just a plain text file; you can either use the following command to create it in Windows, or anyway you like: copy NUL Dockerfile. The sample below contains everything necessary to build and run an image. Comments above each command attempt to provide a bit of clarity:

A cheat with Microsoft Visual Studio

If it happens to have a Visual Studio around, just right click on your main project, select ‘Add’ and then ‘Docker Support…’:

Docker Support in Microsoft Visual Studio 2019.

Usually, for ASP.NET Core, I choose ‘Linux’ as Operating System; at the end it comes cheaper if you want to host it, for example, in Azure.