#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   : Restore the per-VM ACL on the disk files
    Source: https://jbtecwiz.com/support/srv-hyperv-vm-start

    Run as     : Elevated PowerShell on the Hyper-V host
    Expect     : 15 minutes
    Risk       : low
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Files are on local storage or a CSV.

    HOW TO UNDO IT
    icacls with /remove for the identity granted.

    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 5"
    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 '  Restore the per-VM ACL on the disk files' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: low   Reversible   15 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 'Get the VM''s ID -- this is the SID the worker process runs under.' -Command {
    Get-VM -Name 'MyVM' | Select-Object Name, Id, State
}

Invoke-Step -Number 2 -Do 'Look at the current ACL on the VHDX and note whether the VM''s GUID appears.' -Command {
    (Get-Acl 'D:\VMs\MyVM\disk.vhdx').Access | Format-Table IdentityReference, FileSystemRights -AutoSize
}

Invoke-Step -Number 3 -Do 'Grant the VM identity full control on the file.' -Why 'The identity is per-VM and contains the VM''s GUID, so it cannot be copied between hosts or recreated by inheritance.' -Command {
    $vm = Get-VM -Name 'MyVM'
    icacls "D:\VMs\MyVM\disk.vhdx" /grant "NT VIRTUAL MACHINE\$($vm.Id):(F)"
}

Invoke-Step -Number 4 -Do 'If several files are involved -- checkpoints, AVHDX chains -- grant on the folder instead.' -Command {
    icacls "D:\VMs\MyVM" /grant "NT VIRTUAL MACHINE\$($vm.Id):(OI)(CI)(F)" /T
}

Invoke-Step -Number 5 -Do 'The supported alternative is to remove and re-add the disk in the VM''s settings, which makes Hyper-V write the ACL itself.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'The VM starts.' 'White'
Write-Host ''
if (-not $DryRun) {
    Start-VM -Name 'MyVM'
    Get-VM -Name 'MyVM' | Select-Object Name, State
}

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: icacls with /remove for the identity granted.' 'DarkGray'
Write-Rule