DoomOS

Operating System built from the ground up that runs only Doom.

File structure:

kernel: Contains code for the base kernel. The filesystem and display functions are located here.
doom: Contains the source code for Doom. Based on the original id-Software Linux version, it has been modified to run on DoomOS.
libc: DoomOS C Library, contains standard functions and headers (stdlib, stdio and such).

Booting

Grab an ISO from the releases or compile it yourself. You'll need a i686 GCC Crosscompiler.

sh full.sh

and boom, qemu should launch with DoomOS.
If you want to boot on real hardware, burn the generated ISO to a CD or USB.
Personally I like ventoy: https://www.ventoy.net/en/index.html.