Boards.txt - adding boards

I expected that if i edited boards.txt and deleted the uno and yun boards, and restarted 1.6.5 arduino environment, that those choices would dissapear from the boards menu. But they remain.

Similarly editing in a new yun variation did not add a board to the menu. I tried adding text lines for the geeetech iduino yun shield on atmega2560, but saw no new board choice after restart. Help.

When i used board manager in the boards dropdown, and updated arduino avr, then the text that I added to boards.txt. took, and displayed itself in the boards menu.

Then selecting the iduino on mega2560 worked and the bridge example allowed pins to be set and reset via web references like

This was the only pain making geeetech iduino yun behave.

Copy the Arduino core from hardware into the hardware folder in your sketchbook, and edit it there.

Avoid fiddling with the default core, and in general, avoid editing stuff in program files. Windows now tries to "protect" you from modifying files there, in ways that aren't quite the same from vista through 10, and which are highly nonintuitive.