I apologize for introducing a tangent, but I need some help defining a
problem.

Those of us who have studied (or used!) TSM for VE know that the TDP for
SQL Server can receive a signal from Windows Server that something is about
to take a backup. The same signal should trigger any pending writes before
something takes a snapshot and then backs up a restorable disk image.

Are there similar signals (which might not be the right word) in Linux or
various UNIX systems? Assuming a lack of support from an application
vendor, I'd want at least to fire off a script upon receiving that signal
to use existing commands to "freeze" the app,

Are there better idioms I should use with my Linux/UNIX gurus, or is this
simply not an option yet?

Thanks,
Nick