Safe Shutdown and Auto Bootup for Raspberry Pi

Have someone pulling the plug on your project, or perhaps an unstable or unreliable power supply? Here is the fix!

Introduction
Whether it’s a media center, file server, web server, robot, car PC, or an arcade console, a battery-less UPS for the Raspberry Pi gives it enough juice to shutdown properly and then boot back up when sufficient power is restored.

I’ve had one to many times have the power “fail” on my Pis. Many times it is a human “fail” by inadvertently pulling the plug.

Now I don’t need to worry about that anymore.

The idea behind the safe shutdown and restart UPS is based on the function of a shutdown pin on the Pi.

Before going further, a shutdown script on the Pi must work by pulling a GPIO PIN to LOW. Once that is complete, the hardware can then be looked at. I have not (yet) mentioned how this is done as there are plenty of online tutorials out there.”

Link