WUAUCLT

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.

Examples:

C:\> wuauclt /a /DetectNow

C:\> wuauclt /r /DetectNow

“We must always change, renew, rejuvenate ourselves; otherwise we harden” ~ Johann Wolfgang von Goethe

Related:

wuauserv - The Windows Update Service
%systemroot%\WindowsUpdate.log
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate