Scott Hanselman

Getting Started with .NET Core and Docker and the Microsoft Container Registry

March 22, '19 Comments [7] Posted in Docker | DotNetCore
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It's super easy to get started with .NET Core and/or ASP.NET Core with Docker. If you have Docker installed you don't need to install anything to try out .NET Core, of course.

To run a little .NET Core console app:

docker run --rm mcr.microsoft.com/dotnet/core/samples:dotnetapp

And the result:

latest: Pulling from dotnet/core/samples
Hello from .NET Core!
...SNIP...

**Environment**
Platform: .NET Core
OS: Linux 4.9.125-linuxkit #1 SMP Fri Sep 7 08:20:28 UTC 2018

To run a quick little ASP.NET Core website just:

docker run -it --rm -p 8000:80 --name aspnetcore_sample mcr.microsoft.com/dotnet/core/samples:aspnetapp

And here it is running on localhost:8000

Simple ASP.NET Core app under Docker

You can also host ASP.NET Core Images with Docker over HTTPS to with this image, or run ASP.NET Core apps in Windows Containers.

Note that Microsoft teams are now publishing container images to the MCR (Microsoft Container Registry) so they can use the Azure CDN and pull faster when they are closer to you globally. The images start at MCR and then can be syndicated to other container registries.

The new repos follow:

When you "docker pull" you can use tag strings for .NET Core and it works across any supported .NET Core version

  • SDK: docker pull mcr.microsoft.com/dotnet/core/sdk:2.1
  • ASP.NET Core Runtime: docker pull mcr.microsoft.com/dotnet/core/aspnet:2.1
  • .NET Core Runtime: docker pull mcr.microsoft.com/dotnet/core/runtime:2.1
  • .NET Core Runtime Dependencies: docker pull mcr.microsoft.com/dotnet/core/runtime-deps:2.1

For example, I can run the .NET Core 3.0 SDK and mess around with it like this:

docker run -it mcr.microsoft.com/dotnet/core/sdk:3.0 

I've been using Docker to run my unit tests on my podcast site within a container locally. Then I volume mount and dump the test results out in a local folder and inspect them with Visual Studio

docker build --pull --target testrunner -t podcast:test .
docker run --rm -v c:\github\hanselminutes-core\TestResults:/app/hanselminutes.core.tests/TestResults podcast:test

I can then either host the Docker container in Azure App Service for Containers, or as little one-off per-second billed instances with Azure Container Instances (ACI).

Have you been using .NET Core in Docker? How has it been going for you?


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Monday, March 25, 2019 4:29:05 AM UTC
We're using Azure Kubernetes to host Docker containers with .NET Core 2.1 apps (backend and frontend), it's great to scale easily.

Also, we use .NET Core within Docker in the DevOps C.I. (builds) to run no-traditional tests, like execution of the app.
Monday, March 25, 2019 8:41:56 AM UTC
Hosting using Docker is fine. The problem why it's fairly difficult to start using it professionally (everything should be hosted on-premise) is because there are no official Docker Registry images running on Windows and for someone how never used Unix systems it becomes a hurdle.

Additionally building with Docker is still untamed beast for me as I explained in my StackOverflow post: https://stackoverflow.com/questions/55088190/running-npm-ci-when-building-docker-image-is-much-slower

Also this issue: https://stackoverflow.com/questions/53802995/cpu-resources-during-docker-build-command-on-windows

I wish I could build and deploy using Docker images but for now it looks like Docker for Windows is still not there =(
Pavels Ahmadulins
Monday, March 25, 2019 9:06:39 AM UTC
We're run full Windows Container in the company(intranet), not easy work.
Monday, March 25, 2019 9:28:00 AM UTC
Is there some way to find out what ISNT supported in Windows docker images?

(My personal gripe: Windows Media Foundation - want to transcode video? Not in docker!)

I’ve been unable to find any real information about the differences between a docker Windows image and a real OS install.

It kind of undermines the value of containers if they’re not *exactly* the same as the true OS.
Robin Stevens
Monday, March 25, 2019 6:14:53 PM UTC
Could somebody tell which version of Windows is required to run Windows Docker images in production?

If I am reading the licensing correctly, it is Windows Server Datacenter edition. Am I wrong?

Thank you.
TPersistent
Tuesday, March 26, 2019 8:44:19 AM UTC
I am doing a presentation about Docker for Devs. See my work at https://github.com/ignatandrei/Presentations/tree/master/2019/shorts/DockerForDevs
If you have some suggestions, I will be happy to incorporate !
Tuesday, March 26, 2019 11:53:45 AM UTC
Ignat Andrei, check this
Simple docker-compose example of stateful microservice (your own selfhosted private registry) published to internet using automated LetsEncrypt.


To create ./htpasswd file use
docker run  --rm --entrypoint htpasswd registry:2 -Bbn mylogin mypassword  > ~/.htpasswd


docker-compose.yaml

version: '2'
services:
registry:
image: registry:2
restart: always
environment:
VIRTUAL_HOST: registry.blinkov.com
LETSENCRYPT_HOST: registry.blinkov.com
LETSENCRYPT_EMAIL: admin@blinkov.com
REGISTRY_AUTH: htpasswd
REGISTRY_AUTH_HTPASSWD_REALM: 'Registry Realm'
REGISTRY_AUTH_HTPASSWD_PATH: '/auth_htpasswd'
REGISTRY_HTTP_ADDR: '0.0.0.0:5000'
REGISTRY_STORAGE_MAINTENANCE: |-
uploadpurging:
enabled: false
readonly:
enabled: false
REGISTRY_STORAGE_DELETE_ENABLED: 'false'
volumes:
- "/var/lib/registry"
- ~/.htpasswd:/auth_htpasswd
- "~/registry:/var/lib/registry"
nginx-proxy:
image: jwilder/nginx-proxy
restart: always
ports:
- "80:80"
- "443:443"
volumes:
- "/etc/nginx/vhost.d"
- "/usr/share/nginx/html"
- "/var/run/docker.sock:/tmp/docker.sock:ro"
- "/etc/nginx/certs"
- "./my_custom_proxy_settings.conf:/etc/nginx/conf.d/my_custom_proxy_settings.conf"
letsencrypt-nginx-proxy-companion:
image: jrcs/letsencrypt-nginx-proxy-companion
restart: always
volumes:
- "/var/run/docker.sock:/var/run/docker.sock:ro"
volumes_from:
- "nginx-proxy"

This is example. This is not deeply-tested production-ready solution. Nginx need some tuning to be good reverse proxy for production usage.
I am using similar config as ingress in k8s with edited nginx buffers.
Roman Blinkov
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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.