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

    Fault : Hyper-V: a VM will not start -- 0x80070569 or "failed to open attachment"
    Fix   : Fix constrained delegation for SMB-hosted VMs
    Source: https://jbtecwiz.com/support/srv-hyperv-vm-start

    Run as     : Elevated PowerShell
    Expect     : 45 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    VM files are on an SMB 3 file share.

    HOW TO UNDO IT
    Set-ADComputer HV01 -Remove @{'msDS-AllowedToDelegateTo'=...}

    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 4"
    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 '  Hyper-V: a VM will not start -- 0x80070569 or "failed to open attachment"' -ForegroundColor White
Write-Host '  Fix constrained delegation for SMB-hosted VMs' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   45 minutes'
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 'Confirm the host computer account has full control on the share and the NTFS path -- both, not one.' -Manual

Invoke-Step -Number 2 -Do 'Check delegation is configured for the CIFS service on the file server.' -Why 'Without constrained delegation the host cannot present the caller''s credentials to the file server, and the failure surfaces as a permissions error on the VHDX.' -Command {
    Get-ADComputer HV01 -Properties msDS-AllowedToDelegateTo | Select-Object -ExpandProperty 'msDS-AllowedToDelegateTo'
}

Invoke-Step -Number 3 -Do 'Add it if missing.' -Command {
    Set-ADComputer HV01 -Add @{'msDS-AllowedToDelegateTo'=@('cifs/FS01.example.local','cifs/FS01')}
}

Invoke-Step -Number 4 -Do 'Restart the Hyper-V host so the ticket cache is rebuilt.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'The VM starts and the host can browse the share as itself.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-SmbShareAccess -Name VMs -CimSession FS01
}

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-hyperv-vm-start' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Set-ADComputer HV01 -Remove @{''msDS-AllowedToDelegateTo''=...}' 'DarkGray'
Write-Rule