How to Check if a Server Needs a Reboot

If you’re trying to determine which of your servers require reboots, you’ll love this PowerShell script to check the status.

It turns out that a simple way to identify servers that are pending reboot is to check the registry.

This information is stored in the HKeyLocalMachine hive of the registry.

PowerShell is perfect for working with the registry.

Registry is one of the built-in PowerShell providers!

There’s even already a PSDrive connected to that registry hive!

You can’t ask for anything more… except to maybe be able to map a new PSDrive to a different part of the Registry — which is ALSO super easy to do!

You can browse around the registry just like you do with the filesystem.

#Change to the registry drive. 
#Set-Location can also be invoked through its aliases - CD and SL
#Get-ChildItem can also be invoked through its aliases - Dir and LS

Set-Location HKLM:
Get-ChildItem

Wow! Super easy, right?

Now you just need to know where the “pending reboot” location is. There are a couple of places to check.

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired

Is where patches installed through automatic updates register the need to reboot.

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending

Is another place where pending reboots can be identified.

• HKLM\SYSTEM\CurrentControlSet\Control\Session Manager

Is yet another. Finally, there is Configuration Manager which, if present, can be queried via WMI.

I found a function that I really like to check all four locations.

I’ll need to wrap it up with some parameters to check remote computers, but in general it was a great start.

I’ve adapted the function to return $true on the first condition that satisfies, since I only care about whether the computer is pending a reboot, and not where the source of the reboot is coming from.

#Adapted from https://gist.github.com/altrive/5329377
#Based on <https://gallery.technet.microsoft.com/scriptcenter/Get-PendingReboot-Query-bdb79542>
function Test-PendingReboot
{
 if (Get-ChildItem "HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending" -EA Ignore) { return $true }
 if (Get-Item "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired" -EA Ignore) { return $true }
 if (Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager" -Name PendingFileRenameOperations -EA Ignore) { return $true }
 try { 
   $util = [wmiclass]"\\.\root\ccm\clientsdk:CCM_ClientUtilities"
   $status = $util.DetermineIfRebootPending()
   if(($status -ne $null) -and $status.RebootPending){
     return $true
   }
 }catch{}

 return $false
}