Hard Disk – Install Linux on a MacBook Pro 8.1 running Windows 7 only

I installed Windows 7 on my MacBookPro 8.1 via Bootcamp some time ago (and I deleted macOS during the process). Now, I would like to change it to a dual boot system to work with Windows 7 and Linux.

I know I have to repartition my hard drive to do it, but all the instructions I've found require that I start under macOS. How can I accomplish the same thing using only Windows 7 and macOS recovery mode?