Update the Windows hosts file with the WSL2 IP address and additional hostnames

wslhosts.ps1

# Description: Update the Windows hosts file with the WSL2 IP address and additional hostnames.
#  It will add the WSL2 IP address to the hosts file with the hostname `wsl.local`.
#  It will also add any additional hostnames from the `~/.wslhosts` file in the WSL2 home directory.
#
# Usage: `powershell -ExecutionPolicy Bypass -File wslhosts.ps1`
#
# Follow these steps to run the script at each WSL2 boot:
# - Open Task Scheduler
# - Create a new task
# - Set the trigger to run on:
#   - Log: `System`
#   - Source: `Hyper-V-VmSwitch`
#   - Event Id : `102`
# - Set the action to start a program and point it to `powershell.exe` with the script file as an argument:
#   - Program/script: `\Windows\System32\WindowsPowerShell\v1.0\powershell.exe`
#   - Add arguments: `-ExecutionPolicy Bypass -File "C:\path\to\wslhosts.ps1"`
# - Make sure to check these settings are checked:
#   - "Run whether user is logged on or now"
#   - "Run with highest privileges"
# - For a first test, right click on your newly created task and choose "Run now"
#
# Inspired by https://gist.github.com/MichaelBelgium/2243e5713833ba44b5675d844eeb1c85

$wslHostname             = "wsl.local"
$wslDistribution         = "Ubuntu"
$hostsPath               = "$Env:windir\System32\drivers\etc\hosts"
$additionalHostnamesPath = "~/.wslhosts"
$markerStart             = "# WSLHOSTS-START"
$markerEnd               = "# WSLHOSTS-END"

# Make sure we run as Administrator
$user = New-Object Security.Principal.WindowsPrincipal $( [Security.Principal.WindowsIdentity]::GetCurrent() )
if ( $user.IsInRole( [Security.Principal.WindowsBuiltinRole]::Administrator ) -eq $false ) {
    Start-Process powershell.exe -WindowStyle Hidden -Verb RunAs `
        -ArgumentList ( '-noprofile -noexit -file "{0}" -elevated' -f ( $myinvocation.MyCommand.Definition ) )
    exit
}

$wslIp = (wsl -d "$wslDistribution" -- ip addr show eth0 '|' grep 'inet ' '|' cut -f 6 -d ' ' '|' cut -f 1 -d '/')
if (-not $wslIp) {
    Write-Error "WSL is not running"
    exit
}

$additionalHostnames = @()
try {
    $additionalHostnames = (wsl -d "$wslDistribution" -- cat "$additionalHostnamesPath").Replace("`r", "").Split("`n")
} catch {
    Write-Warning "No additional hostnames found in $additionalHostnamesPath file"
}

$content = Get-Content $hostsPath
$newContent = @()
$inMarkerBlock = $false

foreach ($line in $content) {
    if ($line -eq $markerStart) {
        $inMarkerBlock = $true
        continue
    }
    if ($line -eq $markerEnd) {
        $inMarkerBlock = $false
        continue
    }
    if (-not $inMarkerBlock) {
        $newContent += $line
    }
}

$newContent += $markerStart
$newContent += "$wslIp $wslHostname"
foreach ($hostname in $additionalHostnames) {
    $newContent += "$wslIp $hostname"
}
$newContent += $markerEnd

$newContent | Set-Content $hostsPath -Force
Write-Output "Hosts file updated with IP: $wslIp"