Container.init.ps1

<#
.SYNOPSIS
    Initializes a container during build.
.DESCRIPTION
    Initializes the container image with the necessary modules and packages.

    This script should be called from the Dockerfile, during the creation of the container image.

    ~~~Dockerfile
    # Thank you Microsoft!  Thank you PowerShell!  Thank you Docker!
    FROM mcr.microsoft.com/powershell
    # Set the shell to PowerShell (thanks again, Docker!)
    # Copy the module into the container
    RUN --mount=type=bind,src=./,target=/Initialize /bin/pwsh -nologo -command /Initialize/Container.init.ps1
    # Set the entrypoint to the script we just created.
    ENTRYPOINT [ "/bin/pwsh","-nologo","-noexit","-file","/Container.start.ps1" ]
    ~~~
    
    The scripts arguments can be provided with either an `ARG` or `ENV` instruction in the Dockerfile.
#>

#use container mcr.microsoft.com/powershell

param(
# The name of the module to be installed.
[string]$ModuleName = $(
    if ($env:ModuleName) { $env:ModuleName }
    else {
        (Get-ChildItem -Path $PSScriptRoot |
        Where-Object Extension -eq '.psd1' |
        Select-String 'ModuleVersion\s=' |
        Select-Object -ExpandProperty Path -First 1) -replace '\.psd1$'
    }
),
# The packages to be installed.
[string[]]$InstallAptGet = @($env:InstallAptGet -split ','),
# The modules to be installed.
[string[]]$InstallModule = @($env:InstallModule -split ','),
# The Ruby gems to be installed.
[string[]]$InstallRubyGem = @($env:InstallRubyGem -split ','),

# If set, will keep the .git directories.
[switch]$KeepGit = $($env:KeepGit -match $true)
)

# Copy all container-related scripts to the root of the container.
Get-ChildItem -Path $PSScriptRoot | 
    Where-Object Name -Match '^Container\..+?\.ps1$' | 
    Copy-Item -Destination /

# Create a profile
New-Item -Path $Profile -ItemType File -Force | Out-Null

if ($ModuleName) {
    # Get the root module directory
    $rootModuleDirectory = @($env:PSModulePath -split '[;:]')[0]

    # Determine the path to the module destination. 
    $moduleDestination = "$rootModuleDirectory/$ModuleName"
    # Copy the module to the destination
    # (this is being used instead of the COPY statement in Docker, to avoid additional layers).
    Copy-Item -Path "$psScriptRoot" -Destination $moduleDestination -Recurse -Force

    # and import this module in the profile
    Add-Content -Path $profile -Value "Import-Module $ModuleName" -Force
}

# If we have modules to install
if ($InstallModule) { 
    # Install the modules
    Install-Module -Name $InstallModule -Force -AcceptLicense -Scope CurrentUser
    # and import them in the profile
    Add-Content -Path $Profile -Value "Import-Module '$($InstallModule -join "','")'" -Force
}

# If we have packages to install
if ($InstallAptGet) {
    # install the packages
    apt-get update && 
        apt-get install -y @InstallAptGet '--no-install-recommends' && 
            apt-get clean |
                Out-Host
}

if ($InstallRubyGem) {
    # Install the Ruby gems
    gem install @InstallRubyGem
}

if ($ModuleName) {
    # In our profile, push into the module's directory
    Add-Content -Path $Profile -Value "Get-Module $ModuleName | Split-Path | Push-Location" -Force
}

if (-not $KeepGit) {
    # Remove the .git directories from any modules
    Get-ChildItem -Path $rootModuleDirectory -Directory -Force -Recurse |
        Where-Object Name -eq '.git' |
        Remove-Item -Recurse -Force
}

# Congratulations! You have successfully initialized the container image.
# This script should work in about any module, with minor adjustments.
# If you have any adjustments, please put them below here, in the `#region Custom`

#region Custom

#endregion Custom