There are many ways to reset your Raspberry Pi. The most common one is by typing "sudo reboot" command. But you need to have a keyboard or a monitor hooked up for this. The other way is by unplug and plug the power back in or use a power cable with a switch like this.

It is also possible to add a reset hardware for your Pi. There is an unpopulated 2-pin header that will reset the processor when the pins are shorted momentarily. On Model A and B, the header is labelled as "P6" and on the Pi 2 and Model B+ it is labelled as "RUN".

This kit consists of a 45 cm long cable connected to a 2-pole momentary push-button switch and 2 types of 2.54mm pin, straight and right-angle header. You'll need only one type of pin but we include them both so that you can choose the one that suits you better. To install, all you need to do is just solder the pins to the reset header (this voids your warranty, but you probably already know that). Then connect the cable to the pin.

You probably do not want to use this switch very often because like any other computer, you should properly shutdown your Pi. However, there's another nifty feature where the push button can be a simple "ON" switch. When your Pi is in shutdown state while the power is still connected, pressing the button will bring it back to life.