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wuauserv, wuauclt, BITS & svchost.exe.

October 6th, 2012 by Andrea Matesi 4365 Views

wuauserv & wuauclt.

  • wuauserv is the Windows Update service GUI.
  • wuauclt is the CLI util for automatic updates management through cmd.

wuaclt settings:
HKLM\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update

(Please Note that if the previous key doesn't exist, it means the Windows Update feature is disabled).

Manually check if there are Windows Updates:

wuauclt /detectnow

The WUA relies on another service to fetch the WU downloads in the background: the BITS (Background Intelligent Transfer Service).

BITS & svchost.exe.

To gather info about the BITS service:

- Install Process Explorer (http://technet.microsoft.com/en-us/sysinternals/bb896653).

- BITS should be under svchost.exe.

- Or simply execute "tasklist /SVC" for a list of active services in each process that are running in Svchost:

tasklist /svc shows all the process groups under svchost.exe

BITS uses async mode HTTP 1.1 extensions and fetches the Windows Updates while the user is logged on. Once the user logs off, BITS pauses the process, then resumes it once the user is logged on again (it doesn't need to restart the download process from the beginning, it simply continues from where it left like a download manager).

svchost.exe is a process that contains a list of services. At startup, Svchost.exe checks the services part of the registry to construct a list of services that it must load. Multiple instances of Svchost.exe can run at the same time. Each Svchost.exe session can contain a grouping of services.

svchost list of groups from the registry.

Svchost.exe groups List:
HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Svchost

You can install bitsadmin to manage the service status from:

http://msdn.microsoft.com/en-us/library/aa362813%28v=vs.85%29.aspx

Execute from cmd:

bitsadmin /list /allusers (/verbose)

To interrupt downloads:

bitsdamin /cancel filename.zip

To suspend downloads:

bitsdamin /suspend

To restart the job, use the /resume switch.

Bibliography:

http://msdn.microsoft.com/en-us/library/aa362813%28v=vs.85%29.aspx
http://programmazione.it/index.php?entity=eitem&idItem=47364

Develop Auto-Updating Apps with .NET and BITS:
http://msdn.microsoft.com/en-us/magazine/cc188766.aspx

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