SharePoint 2010 | Correct SharePoint behavior | "SharePoint displays users as DomainUsername instead of Display Name"

I have seen this behaviour a number of times in our client enviornments when some of your AD accounts would show - DomainName\UserName  as the display name. In most cases it is the Profile Sync job which is turned off and as a result the synchronization doesn't happen.

But sometimes even the profile sync is on, but SHarePoint 2010 can't update the accounts. In such a case one can - Powershell Command "Set-SPUser".

1) If the problem only appears with a single user, you can update a single account like so:

Set-SPUser -Identity ‘domain\Username’ –Web https://<URL To Site> –SyncFromAD

2) If all (or a lot) of the uesrs you can do it by the following:

Get-SPUser –Web https://<URL to Site> | Set-SPUser –SyncFromAD

The above will reset all users FOR THAT SPECIFIC URL; if you have additional site collections (i.e. Managed Paths), you have to run it on those URL's as well.