I have seen the error could not stat promote trigger file "...": Permission denied
because of a misconfiguration (for example, setting promote_trigger_file to point into a directory to which you don't have appropriate read or execute access).
The problem is that because this happens in the startup process, the ERROR is turned into a FATAL and the whole instance shuts down. That seems like a harsh penalty. Would it be better to turn this ERROR into a WARNING?
-- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services