A few days ago I wrote up a small post on modifying extension attributes for computer objects in Active Directory. I recently set up a lab with Server 2012 and found that extensionattribute1 is now msDS-cloudExtensionAttribute1, and if you just drop in msDS-cloudExtensionAttribute1 without quotes it has issues… This gave me a small headache, after reading this link I found that simply putting quotes around it, fixed it. The following code should work better in a server 2012 enviornment.

import-module activedirectory
$machines = Get-Content "C:\PATH TO LIST\feedme.txt"
foreach($machinename in $machines)
{
    Set-ADComputer $machinename -add @{"msDS-cloudExtensionAttribute1" = "SALOMONTEST"}
    write-host $machinename " is done."
}

If you want to remove an attribute from a list the following should work:

import-module activedirectory
$machines = Get-Content "C:\PATH TO LIST\feedme.txt"
foreach($machinename in $machines)
{
    Set-ADComputer $machinename -clear @{"msDS-cloudExtensionAttribute1"}
    write-host $machinename " is done."
}