File created in cygwin cannot be found

Question

Setup: Cygwin on Windows 8 64bit. UAC enabled.

Scenario: I run cygwin without administrator privilege. I go to a directory and create a new file. Turns out I don't have write access to this directory. Cygwin does not write error message and create the file anyways. I can use this cygwin session to access the file without issues.

However, when I use windows' file explorer, I can't find the file. If I run Cygwin as administrator and go to the same directory, the file is not there. The file shows up only if I run Cygwin without admin privilege. I can't find any documentation of this behavior anywhere.

Where does cygwin put the file? Why can't I see it if I run with administrator privilege?

Thanks

Answer 1

That's Windows' Virtual File Store in action, as introduced with Vista. It redirects unauthorized writes by limited users to C:\Users\Username\AppData\Local\VirtualStore. More on this on MSDN.