WSL Minimal Install

wsl-minimal.ps1

#! /usr/bin/env pwsh
<#
    Notes as code for creating a minimal WSL image.
    This is not docker!
#>
#Requires -Version 7.4
Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'

# TODO: parameterize all these hard-coded vars
$distro = 'Ubuntu'
$ldistro = $distro.ToLower()

# TODO: ver/what are synonyms; use one, presume the other
$ver = '24'
$what = 'noble'

$arch = $env:PROCESSOR_ARCHITECTURE.ToLower()

# TODO: un-hard-code this
$WSLroot = 'D:\Users\Curtis\VMs\WSL'

# TODO: replace these Ubuntu-specific vars with any distribution such as Fedora
$imgfile = "$ldistro-$ver.04-minimal-cloudimg-$arch-root.tar.xz"
$urlbase = "https://cloud-images.ubuntu.com/minimal/releases/$what/"

function main {

    $when = latestimage
    $OutDir = "$WSLroot\$distro\$what\minimal-$when"
    $Uri = "${urlbase}release-$when/$imgfile"
    $wsldistro = "$distro$ver-minimal-$when"

    # fetch the root filesystem image
    wgetN -Uri $Uri -OutDir $OutDir

    # create WSL distro if it doesn't already exist
    $exists = wsl --list --quiet |Select-String -Pattern $wsldistro -SimpleMatch
    if ($exists) {
        Write-Host "Distribution '$wsldistro' exists. Not overwriting."
    } else {
        wsl --import "$wsldistro" "$OutDir" "$OutDir\$imgfile" --version 2

        # save a little time in apt update by turning off Translations-en
        $runcmd = 'echo "Acquire::Languages \"none\";" >/etc/apt/apt.conf.d/99translations'
        wsl --distribution "$wsldistro" -- bash -c "$runcmd"

        wsl --distribution "$wsldistro" -- bash -ex -c @'
            export DEBIAN_FRONTEND=noninteractive
            apt-get update
            apt-get purge \
                amd64-microcode \
                apparmor \
                intel-microcode \
                keyboard-configuration \
                python3-apt \
                python3-cryptography \
                python3-gi \
                snapd \
                ubuntu-pro-client \
                udev \
                --yes
            apt-get install --yes \
                arj \
                atop \
                bzip2 \
                cpio \
                file \
                fuse3 \
                genisoimage \
                git-lfs \
                htop \
                iproute2 \
                less \
                lrzip \
                make \
                mc \
                mtr-tiny \
                net-tools \
                ncdu \
                patch \
                pixz \
                psmisc \
                squashfs-tools \
                strace \
                unzip \
                util-linux-extra \
                zip \
                zstd \
                --no-install-recommends
            apt-get autopurge --yes
            apt-get upgrade --yes
            # apt-get clean
            # rm -r /var/lib/apt/lists/*
'@

        wsl --distribution "$wsldistro" -- bash -ex -c @'
            useradd --create-home --shell=/bin/bash ubuntu
            echo "ubuntu ALL=(ALL:ALL) NOPASSWD:ALL" >/etc/sudoers.d/ubuntu
            echo -e "[user]\ndefault=ubuntu" >/etc/wsl.conf
            find / -mount -maxdepth 1 -empty -type d -name '*.usr-is-merged' -delete
            # dd if=/dev/zero of=/zero.fill bs=1M count=500 status=progress
            # rm /zero.fill
'@

        # # wsl --terminate "$wsldistro"
        # # above might not work since system still seems to hold on to vhdx file!?!
        # wsl --shutdown
        # # TODO: don't do the above if other WSL distros are alive

        # Import-Module Hyper-V
        # Optimize-VHD -Path "$OutDir\ext4.vhdx" -Mode Full
    }

    wsl --list --verbose
}

function latestimage {
    $response = Invoke-WebRequest -Uri $urlbase
    $links = $response.Links |Where-Object { $_.href -match '^release-' } |Select-Object -ExpandProperty href
    return $links[-1].Substring(8).TrimEnd('/')
}

function wgetN {
    param (
        [Parameter(Mandatory = $true)][string]$Uri,
        [string]$OutDir = $PWD
    )

    New-Item -Path $OutDir -ItemType Directory -Force |Out-Null

    # $imgfile = Split-Path -Path $Uri -Leaf
    $OutFile = Join-Path -Path $OutDir -ChildPath $imgfile

    if (!(Test-Path -LiteralPath $OutFile)) {
        $resp = Invoke-WebRequest -Uri $Uri -OutFile $OutFile -PassThru
        # without -PassThru above would be a file object instead of response object with needed headers
        $lm = $resp.Headers.'Last-Modified'
        if ($lm) {
            $rtime = [DateTime]::Parse($lm).ToUniversalTime()
            (Get-Item $OutFile).LastWriteTime = $rtime
        }
        return
    }

    $head = Invoke-WebRequest -Uri $Uri -Method HEAD
    $lm = $head.Headers.'Last-Modified'
    if ($lm) {
        $rtime = [DateTime]::Parse($lm).ToUniversalTime()
        $ltime = (Get-Item $OutFile).LastWriteTime.ToUniversalTime()
        if ($rtime -gt $ltime) {
            Invoke-WebRequest -Uri $Uri -OutFile $OutFile
            (Get-Item $OutFile).LastWriteTime = $rtime
        }
    } else {
        Invoke-WebRequest -Uri $Uri -OutFile $OutFile
    }
}

main