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Title
Font File is held open by System Process

Summary

During a upgrade or uninstall sometimes the installer may require a reboot because font files included in the installer are locked.

Synopsis


This is for Basic MSI projects.

When performing an Upgrade or Uninstall you may notice that the installer requires a reboot due to font files being held by system process.

An example of this issue in the log file is as follows:

RESTART MANAGER: Detected that application with id 4, friendly name 'System', of type RmCritical and status 1 holds file in use.

Whilst there is no direct reference to what files are locked, special notice should be taken of "friendly name 'System'" which denotes that the system process is holding a file.


Discussion


This behaviour was introduced with a Microsoft security update released in August 2015 - see security bulletin MS14-045 for further details.
This applies to any font file that is not installed to the default fonts directory.

After you install this security update, fonts that are installed in a location other than the default fonts directory 
(%windir%\fonts\) cannot be changed when they are loaded into any active session. 
Attempts to change, replace, or delete these fonts will be blocked, and a "File in use" message will be presented.

Whilst the above was listed as a "known issue" it has since been documented by Microsoft and expected behaviour in the msdn article "Font Installation and Deletion"

A font installed from a location other than the %windir%\fonts folder cannot be modified when loaded in any active session, including session 0. 
Any attempt to change, replace, or delete will, therefore, be blocked.




Workaround



If the reboot behaviour is not acceptable for your installation then this could be repressed by using the property: REBOOT=ReallySuppress

Alternatively you should follow Microsoft's new guidelines and install the font files to the default font directory.



Additional Information


Reboot Property
https://msdn.microsoft.com/en-us/library/windows/desktop/aa371101(v=vs.85).aspx

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Font File is held open by System Process