Installing Linux on a MacBook Pro and waranty On a 2014 MacBook Pro Retina, does dual-booting the pre-installed OS X with Linux (say Ubuntu/Debian/Fedora/etc) void the hardware warranty? Does installing Linux and removing OS X void the hardware warranty?

I do not mind the entire hard disk being erased and set to a default OS X install if the machine has to be given for repair under warranty.

If you're going to suggest "reinstall OS X yourself before giving for repair", yes, that is an option if some non-essential component of the machine stops working. But it's not an option if the machine won't boot at all, which is when you'll be in need of servicing the most.

The country of purchase is India, if it matters.
Installing Linux or any other OS on your Mac does not void your warranty as provided here:

https://www.apple.com/legal/warranty/products/embedded-mac-warranty-row.html

The only thing you should be concerned about if anything is the fact that Apple will not provide support for Linux if you choose to install it on your Mac.

If you were to experience issues with Linux on your Mac that you suspected were hardware related, Apple can run a hardware diagnostic on the Mac even if OS X is uninstalled from it. So if you ever ran into an issue where your Mac wouldn't start up as you described in your question, Apple should be able to diagnose the issue and get you a repair provided your Mac is still covered under AppleCare.