Summary

Synopsis

This article provides information on how deferred in system context actions run when installing per-user (ALLUSERS is not set).

Discussion

Custom actions that have an in-script execution setting of deferred in system context are used to perform an action with the rights granted to the local SYSTEM account on Windows, as the Windows Installer service runs in the SYSTEM context. Actions not marked as deferred in system context run with user impersonation, and have the rights that the user that launched the installation has.

• The user that launched the MSI installation is not an administrator, or is running on Windows Vista, in which users are part of the administrators group, but do not have administrator privileges by default.
• The custom action attempts to modify a resource in a per-machine location on the machine, such as a file in Program Files, or a registry key/value in HKEY_LOCAL_MACHINE in the registry.

Additional Information

More information can be found in the following articles:

• ALLUSERS Property
• Custom Action In-Script Execution Options
• Tao of the Windows Installer, Part 3 - Rule 30
• UAC in MSI Notes: The NoImpersonate Bit Mistake