#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : SYSVOL not shared, or Group Policy files missing on one controller
    Fix   : Rebuild SYSVOL authoritatively
    Source: https://jbtecwiz.com/support/srv-id-sysvol

    Run as     : Elevated PowerShell
    Expect     : 2 hours
    Risk       : high
    Reversible : NO -- read the undo note below before running

    WHEN THIS IS THE RIGHT FIX
    Every controller is affected. One copy has to be nominated as correct.

    HOW TO UNDO IT
    Restore the backup taken in step one into the authoritative controller's
    SYSVOL and repeat.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 6"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  SYSVOL not shared, or Group Policy files missing on one controller' -ForegroundColor White
Write-Host '  Rebuild SYSVOL authoritatively' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: high   NOT REVERSIBLE   2 hours' -ForegroundColor Yellow
Write-Host ''
Show-Prose 'Undo: Restore the backup taken in step one into the authoritative controller''s SYSVOL and repeat.' 'Yellow'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Back up the SYSVOL contents from the controller with the most complete copy, before anything else.' -Why 'An authoritative restore discards every other copy. If the one you nominate turns out to be missing policies, this backup is the only route back.' -Command {
    Copy-Item C:\Windows\SYSVOL\domain -Destination D:\sysvol-backup -Recurse -Force
}

Invoke-Step -Number 2 -Do 'Check every controller''s copy before choosing which is authoritative.' -Command {
    Get-ADDomainController -Filter * | ForEach-Object {
      $n = $_.HostName
      [PSCustomObject]@{ DC = $n; Policies = (Get-ChildItem "\\$n\SYSVOL\$env:USERDNSDOMAIN\Policies" -ErrorAction SilentlyContinue).Count }
    }
}

Invoke-Step -Number 3 -Do 'Stop the DFSR service on every controller.' -Command {
    Get-ADDomainController -Filter * | ForEach-Object { Invoke-Command -ComputerName $_.HostName { Stop-Service DFSR -Force } }
}

Invoke-Step -Number 4 -Do 'On the chosen controller, set msDFSR-options to 1 and Enabled to false, then start DFSR, wait for event 4114, set Enabled true and restart.' -Command {
    $dn = (Get-ADDomainController -Identity $env:COMPUTERNAME).ComputerObjectDN
    Set-ADObject -Identity "CN=SYSVOL Subscription,CN=Domain System Volume,CN=DFSR-LocalSettings,$dn" -Replace @{ 'msDFSR-Enabled'=$false; 'msDFSR-options'=1 }
}

Invoke-Step -Number 5 -Do 'Set every other controller non-authoritative and start them, one at a time, confirming each completes before the next.' -Manual

Invoke-Step -Number 6 -Do 'Wait for event 4602 on the authoritative controller, which confirms the initial sync completed.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'Every controller shares SYSVOL and the policy count matches across all of them.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-ADDomainController -Filter * | ForEach-Object { "$($_.Name): " + (Get-ChildItem "\\$($_.HostName)\SYSVOL\$env:USERDNSDOMAIN\Policies").Count }
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-id-sysvol' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Restore the backup taken in step one into the authoritative controller''s SYSVOL and repeat.' 'DarkGray'
Write-Rule