Looks like we are in the same rabbit-hole. I started out with the same question as you posted, and it looks like you are on to the answer - setup a VM localy or on Azure and you are good to go. The links in the answer from "Leo Liu" is probably a good place to start. However - VMs are not Docker and this doesn't answer your broader question.
If the question is rephrased as "Why don't Microsoft provide an easy way to setup self-hosted agents in docker containers?" I believe the answer lies in their business model. Local VMs need Windows licenses and Azure VMs are billed by the hour...
But, conspiracy theories aside, I don't think there is an easy way to setup a dockerised version of the cloud-hosted agents. It's probably not a very good idea either. Docker containers are meant to be small, and with all of the dependencies on those agents they are anything but small. It's also never going to be "perfect", as you say, since the dockerized windows isn't identical to what's running in their cloud-hosted VMs.
I have started tweeking something that is not perfect, but might work:
- setup a docker-agent according to the documentation here
- add the essence from the PS-scripts corresponding to the packages you need from here
- add commands to the Dockerfile to
COPY and RUN the scripts
docker build as usual and you should have a container that's a bit more capable and an agent that reports its capabilities in a similar way to the cloud-agents
In an ideal world there would be a repository with all of the tweeked scripts, and a community that kept them updated. In an even more ideal world that would be a Microsoft hosted repository, but like I said - that's probably unlikely.
Here is some code to get you started. Maybe I'll publish a more finished version somewhere in the future.
init.ps1 with some lines borrowed from here:
Write-Host "Install chocolatey"
$chocoExePath = 'C:\ProgramData\Chocolatey\bin'
if ($($env:Path).ToLower().Contains($($chocoExePath).ToLower())) {
Write-Host "Chocolatey found in PATH, skipping install..."
Exit
}
$systemPath = [Environment]::GetEnvironmentVariable('Path', [System.EnvironmentVariableTarget]::Machine)
$systemPath += ';' + $chocoExePath
[Environment]::SetEnvironmentVariable("PATH", $systemPath, [System.EnvironmentVariableTarget]::Machine)
$userPath = [Environment]::GetEnvironmentVariable('Path', [System.EnvironmentVariableTarget]::User)
if ($userPath) {
$env:Path = $systemPath + ";" + $userPath
}
else {
$env:Path = $systemPath
}
Invoke-Expression ((new-object net.webclient).DownloadString('https://chocolatey.org/install.ps1'))
choco feature enable -n allowGlobalConfirmation
Remove-Item -Path $env:ChocolateyInstall\bin\cpack.exe -Force
Import-Module "$env:ChocolateyInstall\helpers\chocolateyInstaller.psm1" -Force
Get-ToolsLocation
Modified Dockerfile from the Microsoft documentation, that also runs the script on build:
FROM mcr.microsoft.com/windows/servercore:ltsc2019
COPY init.ps1 /Windows/Temp/init.ps1
RUN powershell -executionpolicy bypass C:\Windows\Temp\init.ps1
WORKDIR /azp
COPY start.ps1 .
CMD powershell .\start.ps1
GenerateResourcesAndImagefromhelpers\GenerateResourcesAndImage.ps1as described in the instructions. – hey