Docker

Hosting Docker Containers

• Use a Docker hosting/management platform (like Rancher, Cloud Foundry, OpenShift, Azure, AWS)
  • no extra web server needed (provided by Docker hosting/management platform)
  • DevOps teams take care of web server and security
• You can do Container Management yourself using Kubernetes (needs more work and knowledge)
  • Docker hosting/management platforms often have Kubernetes inside

Terminology

Image: build of an app Container: instance of a build

Installation Hints - Troubleshooting - only needed of Docker for Windows is not running

Hyper-V

Docker needs Hyper-V (needs to disable VirtualBox)

check Hyper-V Manager

VirtualBox installed: Disable VirtualBox, activate Hyper-V

Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All

Hyper-V for Docker needed Hyper-V Manager

bcdedit /set hypervisorlaunchtype off (deactivate Hyper-V)
bcdedit /set hypervisorlaunchtype auto (reactivate Hyper-V)

reboot

press info-button to activate hyper-v when docker starts

Check WSL

https://learn.microsoft.com/en-us/windows/wsl/install-manual

Basics

Dockerfile

dockerfile = Recipe to create a docker image

simple Dockerfile

FROM node:latest

WORKDIR /app

COPY . .

RUN npm install

EXPOSE 3000

ENTRYPOINT ["node", "app.js"]

Run dockerfile

docker build .

Images

build image (use slash as namespace separator)

Create hello World node app: https://medium.com/@adnanrahic/hello-world-app-with-node-js-and-express-c1eb7cfa8a30

docker build -t <image-name> .
example:
docker build -t bopa/node:latest .

show all images

docker images

BEWARE: delete image

docker image rm <name>
or
docker rmi <container>

BEWARE: Remember, you should remove all the containers before removing all the images from which those containers were created.

BEWARE: To delete all the images, run this:

docker rmi -f $(docker images -a -q)

Delete all unused images

docker image prune

Get information - A Software Bill Of Materials (SBOM)

docker sbom <image name>

Container (instance of image)

Start container

docker run -p 8000:3000 <image-name>
example:
docker run -p 8000:3000 bopa/node

App will run on Port 8000 (3000 is internal port)

Stop all containers (bash)

docker stop $(docker ps -a -q)

BEWARE: To delete all containers including its volumes use (in bash)

docker rm -vf $(docker ps -a -q)

Remove container by container-name

docker rm $(docker stop $(docker ps -a -q --filter name=containerName1 --format="{{.ID}}"))

Delete all unused containers

docker container prune

Volume

Volumes or data volumes is a way for us to create a place in the host machine where we can write files so they are persisted.

Create

docker volume create <name of volume>

List

docker volume ls

Inspect

docker inspect <name of volume or container>

Find IP address:

docker inspect -f "{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}" <containername>

Delete

docker volume rm <name of volume>

Delete all unused volumes

docker volume prune

Connect to running docker container

docker exec -it <containername> bash

System

BEWARE: delete everything

docker system prune -af

Demo From Docker

Details/Source: https://github.com/docker/getting-started

Clone:

git clone https://github.com/docker/getting-started.git

Build:

cd getting-started
docker build -t docker101tutorial .

Run:

docker run -d -p 80:80 \ --name docker-tutorial docker101tutorial

Run detached container with port mapping

docker run -d -p 8888:80 --name container-name> <image-name>

Pull/Push to docker hub

docker pull <dockerhubuser>/<imagename>[:tag]
docker push <dockerhubuser>/<imagename>

Pull/Push to a registry

docker pull <registry>/<url>[:tag]
docker push <registry>/<url>

List all available tags:

docker pull -a <registry>/<url>

Share: (optional)

docker tag docker101tutorial {userName}/docker101tutorial
docker push {userName}/docker101tutorial

Start:

Press the play button in the "Docker Desktop" app.

If you are running a webserver on localhost (like IIS), you have to stop it first. Otherwise the container won't start.

http://localhost/

Continue this Tutorial in the Browser now.

ASP.NET Core Examples

Windows vs. Linux Containers

• Linux does not support Windows Authentication

Difference in csproj

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <DockerDefaultTargetOS>Windows</DockerDefaultTargetOS>
  </PropertyGroup>

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
  </PropertyGroup>

Tutorials

Build inside container vs. build outside container

Compare: build inside vs. build outside container: https://docs.docker.com/samples/dotnetcore/

Dockerize an ASP.NET Core application (build within container)

https://docs.microsoft.com/en-us/visualstudio/containers/container-build?view=vs-2019

Create new WebApi project in Visual Studio, option [x] Enable Docker checked

Empty WebApi Project contains WeatherForecast Controller and this Dockerfile:

#See https://aka.ms/containerfastmode to understand how Visual Studio uses this Dockerfile to build your images for faster debugging.

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["WebApplication1/WebApplication1.csproj", "WebApplication1/"]
RUN dotnet restore "WebApplication1/WebApplication1.csproj"
COPY . .
WORKDIR "/src/WebApplication1"
RUN dotnet build "WebApplication1.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "WebApplication1.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "WebApplication1.dll"]

Run Project from Visual Studio within Docker

Make sure, app is running in 'Docker' (not Kestrel, not IISExpress) and press F5.
While app is running in Docker now, you are even able to debug the app. (set a breakpoint to confirm)

Windows Container

Go to folder of csproj and build the container

docker build -t bopa/aspnetcore_windows -f Dockerfile ..

Start the container

docker run -p 8001:80 bopa/aspnetcore_windows

Test WebApi: http://localhost:8001/weatherforecast

Linux Container

Go to folder of csproj and build the container

docker build -t bopa/aspnetcore_linux -f Dockerfile ..

Start the container

docker run -p 8002:80 bopa/aspnetcore_linux

Test WebApi: http://localhost:8002/weatherforecast

Dotnet Core Examples

• https://hub.docker.com/_/microsoft-dotnet
• Samples: https://github.com/dotnet/dotnet-docker/blob/main/samples/README.md
• Lerman/Ardalis: https://github.com/ardalis/pluralsight-ddd-fundamentals
• EShop on Containers: https://github.com/dotnet-architecture/eShopOnContainers

Todo - how to solve resource access in containers

• web server?
  • reverse proxy?
    • complete example with nginx: https://github.com/referbruv/ContainerNinja.CleanArchitecture
• authorization
  • todo: poc
  • client side certificate in nginx?
    • (how) can .NET Core access this certificate?
  • OIDC
• authentication
  • todo: poc
  • LDAP queries from linux container to Windows AD?
• logging
  • use standard .NET Core logging: will send log to STDOUT and STDERR: TODO: how to log this output?
  • use Splunk or ElasticSearch? https://docs.docker.com/config/containers/logging/configure/#supported-logging-drivers
• file access
  • Windows NAS allowed from Linux? I don't think so...
  • use Unix NAS? mount is not allowed within container. Mount outside using docker run ... --mount ...
  • Evaluate File Storage Api? (Azure File Storage, Azure Blob Storage, ...)
• config from outside (connection strings, SMTP server, ...)
  • set environment variables (will override config)

Information

6 Things To Know When Dockerizing Microsoft .NET Apps in Production

• It is essential to choose the right base image for your container. The smaller your image, the faster it deploys and starts
• Always use a non-root container. Non-root containers add an extra layer of security and are recommended for production environments. Handle SIGINT and SIGTERM in your application so that you can shut down your application gracefully.
• Use Health checks to tell Docker or your cluster manager about the state of your running container.
• Don’t log to files or databases. Always use stdout and stderr. Use the default logging API with a built-in logging provider.
• By default, a .NET 5.0 application provides much functionality to configure your application. You can overrule all settings via Environment variables.

Source: https://levelup.gitconnected.com/6-things-to-know-when-dockerizing-microsoft-net-apps-in-production-45b8c27a41b0

Kubernetes is dropping Docker support - What does it mean for YOU?

• Blog: https://kubernetes.io/blog/2020/12/02/dont-panic-kubernetes-and-docker/
• Video: Nothing for Developers and DevOps, according https://youtu.be/7KUdmFyefSA?t=289