How to get missing Computernames in a Active Directory OU

Question

I would like to get missing computer hostnames in our Active Directory.

Currently we have a naming convention for notebooks:

NB-DE-00001 

and for PC's:

PC-DE-00001

Currently, however, some hostnames have not been incremented, but a higher number has simply been chosen manually.

In AD, for example

NB-DN-00001
NB-DE-00004

Now I would like to determine the missing ones so 2-3 in this example.

Is there a PowerShell way to do this?

Answer 1

There are going to be a number of ways to do this. But this is a decent starting point to list all of the missing numbers in five-digit format.

$Computers = Get-ADComputer -Filter "Name -like '*-*'" -SearchBase 'OU Path' |
    Where Name -match '-\d+$' | Select-Object -Expand Name
[int[]]$UsedNumbers = $Computers -replace '.*?-(?=\d+$)' | Sort-Object { [int]$_ }
1..$UsedNumbers[-1] | Where {$_ -notin $UsedNumbers} |
    Foreach-Object { "{0:d5}" -f $_ }

You have not specified if NB-DE-* , NB-DN-* , or PC-DE-* use the same pool of numbers, if those systems share the same OUs, or if PC-DE-00001 can coexist with NB-DN-00001 .

Answer 2

I just found a really dirty workaround but it works.. For me as a beginner it's okay but I would like to improve my skills so I would appreciate it when you guys could give me some tips.

My solution right now:

My first step is to get a sorted list of computers and notebooks (I just need theese filters for stuff)

$ADnbSorted = Get-ADComputer -SearchBase 'OU=computers,dc=example,dc=com' -Filter {(Name -like "NB-DE-*") -and (Name -notlike "NB-DE-M*") }| Sort-Object | Select-Object Name

$ADpcSorted = Get-ADComputer -SearchBase 'OU=computers,dc=example,dc=com' -Filter {(Name -notlike "PC-DE-R*") -and (Name -like "PC-DE-*") } | Sort-Object | Select-Object Name

My next step is that I create a template list how a correct list of hostnames should look like

$templatehostname = 1..$ADpcSorted[-1].Name |
         ForEach-Object{ "$prefix" + $_.ToString("00000")}

I use prefix because its an little application where the user can enter if he wants to know all PC's Unkown and all Notebook Unkown Hostnames :)

After that I just compare both of theese and add the missing entrys just to a new list

> ForEach($Hostname in $templatehostname) 
>     {
>         if (-Not ($ADpcSorted.Name.Contains($Hostname))) 
>     {  
>     $freeHostname += $Hostname 
>      }
>      }

I'm sorry for that bunch of shit :)