Description of the Windows Update Standalone Installer in Windows

Introduction

This article describes the Windows Update Standalone Installer (Wusa.exe) in the following Windows operating systems:

  • Windows Vista

  • Windows Server 2008

  • Windows 7

  • Windows Server 2008 R2

  • Windows 8

  • Windows Server 2012

  • Windows 8.1

  • Windows Server 2012 R2

  • Windows 10

  • Windows Server 2016 Technical Preview

The Wusa.exe file is in the %windir%\System32 folder. The Windows Update Standalone Installer uses the Windows Update Agent API to install update packages. Update packages have an .msu file name extension. The .msu file name extension is associated with the Windows Update Standalone Installer.

More Information

An .msu file contains the following contents.

Content

Description

Windows Update metadata

Describes each update package that the .msu file contains.

One or more .cab files

Each .cab file represents one update.

An .xml file

This .xml file describes the .msu update package. Wusa.exe uses the .xml file when you perform an unattended installation of the update by using the Package Manager tool (Pkgmgr.exe).

For example, you download hotfix 934307. The Windows6.0-KB934307-x86.msu file is in the C:\934307 folder. You type the following command at a command prompt to expand the .msu file to a temporary folder:

expand -f:* "C:\934307\Windows6.0-KB934307-x86.msu" %TEMP%
Then, you type the following command at a command prompt:

pkgmgr.exe /n:%TEMP%\Windows6.0-KB934307-x86.xml

A properties file

This file contains string properties that Wusa.exe uses. For example, this file contains the title of the associated article in the Microsoft Knowledge Base.



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:

wusa.exe d:\934307\Windows6.0-KB934307-x86.msuYou 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:

Using Software Explorer in Windows Defender
You can use the following switches together with Wusa.exe.

Switch

Description

/?, /h, /help

View help.

/quiet

Run Wusa.exe in quiet mode without user interaction. When the tool runs in quiet mode, it runs without user interaction. The computer restarts if this is required.

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 without user interaction:

wusa.exe d:\934307\Windows6.0-KB934307-x86.msu /quiet
Note When you use this switch, the Microsoft Software License Terms do not appear.

/norestart

Prevents Wusa.exe from restarting the computer. The /norestart switch is ignored if the /quiet switch is not present. If you run Wusa.exe together with these two switches, you must manually restart the operating system after the installation is complete if the installation requires you to restart the computer.

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:

wusa.exe D:\934307\Windows6.0-KB934307-x86.msu /quiet /norestart

/uninstall

Uninstalls the specified package or KB number.

/kb

Specifies the package to be uninstalled by using its KB number. Can be passed only together with the /uninstall switch.

/extract

Wusa.exe extracts the package contents to a destination folder.

/warnrestart

When this switch is combined with the /quiet switch, Wusa.exe prompts you before it begins a restart for install and uninstall operations.

/forcerestart

When this switch is combined with the /quiet switch, Wusa.exe forcibly closes applications and then begins a restart.



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:

Operating System Package Servicing Command-Line Options
To view the Windows Update Standalone Installer event log, follow these steps:

  1. Click Startwindows icon , 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.

    Notice icon 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.

References

For more information about the Windows Update Agent API, go to the following Microsoft website:

Windows Update Agent (WUA) API Reference

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