What is Wusa.exe, Uses, Command Line Information

The wusa.exe file is an executable file that installs update packages on Windows 10 and older versions. The Windows Update Standalone Installer is a component of Microsoft Windows, and can only install update packages with extension .msu. These updates are ‘standalone’ as they not provided directly by Windows Update.

The full form of WUSA is the Windows Update Standalone Installer.

File Size & Location

The wusa.exe comes by default with the Windows Operating System and is located under C:/Windows/System32/ directory. The average file size of wusa.exe is 303 KB in Windows 10 and older versions.

Quick Overview

How wusa.exe work?

The installation files come with .msu files that contain the following material:

1. Metadata: Here wusa.exe uses the Windows Update metadata information to find the latest updates
2. Singular or more .cab files: One .cab file equals one update.
3. .xml file: This file designates the update package. When the installation can’t be completed then wusa.exe uses the .xml file.
4. Properties files: This process uses certain string properties that the. msu file contains.

It is important to note that the Windows Update Standalone Installer uses the Windows Update Agent API for the installation of update packages and can install these packages only one at a time.

WUSA.EXE Update Package Installation Process

1. After using the metadata in order to find out the suitable updates, the contents are copied by the wusa.exe process to Windows Update Sandbox, which is protected.
2. The applicable functions are arranged by wusa.exe in the Windows Update Agent, corresponding to the mode you started with.
3. Once the above process is done then the update package is finished installing by the Update Wizard.

Common Errors

The most common wusa.exe errors are runtime or accessibility errors. Although any such errors are generally rare, there might be issues wherein the installation process does not run smoothly. A few solutions to these problems are:

1. Changing the mode: Trying to install an update package incompatible with your system may result in faulty installation. You can either upgrade to the latest system or, if you’re not willing to pay for it, you can run the compatibility troubleshooter and restart your computer. One should be aware that the latter method is a long shot and might not always work.
2. Reset The Permissions Regarding Windows Update Services: If changing the mode still doesn’t yield any results, then accessibility might be the cause of delayed installation. Many times your antivirus software denies access to the wusa.exe file or you don’t have permission to run the file. If that occurs, check your antivirus log and change the permissions.
3. Reinstall Installer Application: A wusa.exe can be damaged with some flawed program code or missing a DLL file, in both cases you’ll have no option but the reinstall the Standalone Installer application.

One particularly mysterious error is the “only one instance of wusa.exe is allowed to run.” A few fixes for this error are:

1. Make sure that the Windows Installer service is running.
2. In the Task Manager, end the wusa.exe process.
3. To find the source of the error, filter through the Event log, and select WUSA.
4. Reinstall the Windows Installer Service.

Aside from these errors, there can also be issues with the origin of wusa.exe. Do remember that malware often imitates programs with the .exe file extension and one should know not to download any wusa.exe links found in any email.

Sample wusa.exe Commands

Since Windows Update Standalone Installer runs manually, here are a few command-line switches that can be employed along with wusa.exe.

1. /help, /?: Displays help for a user query.
2. update: View the complete process of the .msu file.
3. /quiet: The entire process runs without user interaction and will reboot automatically if necessary. Please note that using this mode means that the Microsoft Software License Terms will not appear.
4. /norestart: Used in combination with the quiet switch, the application will not reboot at all.
5. /warnrestart: Used in combination with the quiet switch, the application will notify the user before rebooting.
6. /forcerestart: Used in combination with the quiet switch, the application will shut down all other programs and force a reboot.
7. /uninstall: This switch will uninstall the update package.
8. /kb: Can only be used in conjunction with the uninstall switch and specifies the package to be uninstalled using the KB number.

Here is one sample command line that you can execute using wusa, all you have to type is wusa /? and this will launch the help file.

Example of the uninstall command: wusa/uninstall<<update>>|kb:<<KB Number>>

9. /log: The application will initiate logging.
10. /extract: wusa.exe will extract the content of the update package and transfer them to another destination folder.

Example of extract command: wusa<update>/ extract:<destination>[/log:<file name>]

The default mode of wusa.exe is an interactive mode. When using this mode, you will be made aware of all the advanced level information of the update packages and the entire process is undertaken.

Also read:

• How to disable Windows installer service
• What is TrustedInstaller.exe
• utweb.exe