In this post I explain the ins and outs of network booting Raspberry Pis. Some Raspberry Pi models can do this without local persistent storage, and most other modelsc can boot with a minimum of data from an SD card. The operating system used is Arch Linux ARM. After booting the system and as long as it has a network connection to a server hosting the Pi's file system, it can be used as any other Pi that was booted from an SD card.
In this post I explain how to modify an aging network attached storage device with a Linux distribution that will keep its software and functionality up-to-date for the foreseeable future.