SharePoint 2010: after domain rename

Add-PSSnapin Microsoft.SharePoint.Powershell

$rootWeb = Get-SPWeb "yoursite"

$oldDomain = "yourOldDomain"

$newDomain = "yourNewDomain"

#loop through all users in the $rootWeb, change the login name and execute the EnsureUser method

foreach ($user in $rootWeb.Users) {

  $newLogin = $user.UserLogin -replace $oldDomain, $newDomain

  $rootWeb.EnsureUser($newLogin)

}