Description of the Windows Update Standalone Installer in Windows

An .msu file contains the following contents.



When you use Wusa.exe to install an update package, Wusa.exe expands the contents of the .msu file to a temporary folder. Then, Wusa.exe performs the following steps:

1. Wusa.exe uses the Windows Update metadata in the .msu file to search for applicable updates.
2. Wusa.exe copies the contents of the applicable updates to the Windows Update sandbox. The Windows Update sandbox is a protected folder.
3. Wusa.exe calls the appropriate function in the Windows Update Agent API according to the mode in which you start Wusa.exe.
4. When the Windows Update wizard finishes the installation, the Windows Update Agent API returns a status. Then, Wusa.exe works synchronously with the Windows Update Agent API.

Note Each update in an .msu update package is installed in a separate session. Only one instance of Wusa.exe runs when you use Wusa.exe. Wusa.exe does not change the contents of the updates in .msu files. The Windows Update infrastructure performs the required actions according to the contents of the update.

When you start Wusa.exe in interactive mode, a welcome screen displays high-level information about the update. If you continue to install the update, Wusa.exe calls the appropriate function in the Windows Update Agent API to start the Windows Update wizard. The Windows Update wizard displays the Microsoft Software License Terms that are associated with the update package. Wusa.exe calls the Windows Update Agent API to continue the installation. Then, Wusa.exe waits until the Windows Update wizard finishes the installation.

To install an .msu update package, run Wusa.exe together with the full path of the file.

For example, if the Windows6.0-KB934307-x86.msu file is in the D:\934307 folder, type the following command at a command prompt to install the update package:You can also double-click the .msu file to install the update package.

You can use Wusa.exe to uninstall an update in Windows 7, Windows Server 2008 R2, Windows 8, and Windows Server 2012.

Note You cannot use Wusa.exe to uninstall updates in Windows Vista or Windows Server 2008. You can use Windows Defender Software Explorer to manually uninstall the updates. For more information about Software Explorer, go to the following Microsoft website:
You can use the following switches together with Wusa.exe.



Note The .msu files can be installed to an offline image by using the DISM.exe /Add-Package option together with the Windows 7 or Windows 8 OEM Preinstallation Kit (OPK) or the Windows Automated Installation Kit (AIK). For more information, go to the following Microsoft TechNet website:


To view the Windows Update Standalone Installer event log, follow these steps:

1. Click Start
   
    , type event viewer in the Start Search box, and then click Event Viewer in the Programs list. In Windows 8 and Windows Server 2012, on the Start screen, type event viewer, click Settings, and then click View event logs under Settings.
   
   
   
    If you are prompted for an administrator password or for confirmation, type the password, or click Continue.
   
   
2. In Event Viewer, expand Windows Logs, and then click Setup.
   
   Setup events appear in the middle pane.
   
   
3. In the Actions pane, click Filter Current Log.
   
   
4. In the Event sources list, click to select the WUSA check box, and then click OK.