I’ve been running a worklet to detect reboots based on

• Windows Update Pending
• Uptime exceeds 28 days

Started noticing many workstations pending a reboot were not triggering on the evaluation code. 

$sysInfo = New-Object -ComObject "Microsoft.Update.SystemInfo"

While there is a way to likely tune above, I’ve opted to add another strategy. This includes a registry lookup using 32-bit Powershell as this key will need it.

# Query WMI for LastBootUpTIme
$uptime = (get-date) - (gcim Win32_OperatingSystem).LastBootUpTime

# Check Registry for Windows Update Pending Update
$scriptblock = {
    function Get-WUAURebootReq {
        ## Making registry connection to the local/remote computer
        $HKLM = KUInt32] "0x80000002"
        $WMI_Reg = RWMIClass] "\\$ENV:COMPUTERNAME\root\default:StdRegProv"

        ## Query WUAU from the registry
        $RegWUAURebootReq = $WMI_Reg.EnumKey($HKLM,"SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\")
        $WUAURebootReq = $RegWUAURebootReq.sNames -contains "RebootRequired"
        Return $WUAURebootReq
    }
    Get-WUAURebootReq
}
$reboot = & "$env:SystemRoot\sysnative\WindowsPowerShell\v1.0\powershell.exe" -ExecutionPolicy Bypass -WindowStyle Hidden -NoProfile -NonInteractive -Command $scriptblock

# Check with COM Object
$sysInfo = New-Object -ComObject "Microsoft.Update.SystemInfo"

if($reboot -eq $true -or $uptime.Days -gt 28 -or $sysInfo.RebootRequired){ 
  exit 1 # reboot is needed
}else{
  exit 0 #no reboot is needed
}