Windows Update Agent, download new Windows Update files.
Syntax wuauclt Options Options: /a or /ResetAuthorization Initiate an asynchronous background search for applicable updates. If Automatic Updates are disabled, this has no effect. /r or /ReportNow Send all queued reporting events to the server asynchronously. /DetectNow Initiate detection right away, Query the WSUS server immediately to see if any new updates are needed.
WSUS uses a cookie on client computers to store computer group membership when client-side targeting is used. By default this cookie expires an hour after WSUS creates it. If you are using client-side targeting and change group membership, use /ResetAuthorization /detectnow to expire the cookie, initiate detection, and have WSUS update computer group membership.
C:\> wuauclt /a /DetectNow
C:\> wuauclt /r /DetectNow
“We must always change, renew, rejuvenate ourselves; otherwise we harden” ~ Johann Wolfgang von Goethe
wuauserv - The Windows Update Service