HOWTO :: Serve custom config to all Yealink UADs on the system

In the /tftp/ folder create y000000000000.boot file and put following in:

nano /opt/pbxware/pw/tftp/y000000000000.boot

#!version:1.0.0.1

include:config "$MAC.cfg"

include:config "y000000000000.cfg"

Next, create y000000000000.cfg file, and in it put whatever static configuration you want for ALL phones 

nano /opt/pbxware/pw/tftp/y000000000000.cfg

overwrite_enable = 1

This should enable you to overwrite configuration via custom provisioning template which is already by default served via provisioning to the phone such as Transport, etc.