Summary

Synopsis

Discussion

Files with the extension .msu are related to the Windows Update Stand-alone Installer. When you use Wusa.exe to install an update package, Wusa.exe expands the contents of the .msu file to a temporary folder. The .msu is expected to include:

1) Windows Update metadata - This metadata describes each update package that the .msu file contains.
2) One or more .cab files - Each .cab file represents one update.
3) An .xml file - This .xml file describes the .msu update package.
4) A properties file - This file contains string properties that Wusa.exe uses.

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 modify the contents of the updates in msu files. The Windows Update infrastructure performs the required actions according to the contents of the update.

Additional Information