My adroid has been updating for 8 hours and phone is unusable what can I do?

[AC Question]

Samsung galaxy 5....upgrading software for approx. 8 hours. The screen says finishing reboot and has not changed for 7 1/2 hours. What can I do?????

 

[TenshiNo]

At this point, it's either done and doesn't realize it, or it's not likely to ever finish. I would recommend forcing it to power off, then turning it back on. I'm going to CYA on this and say that I'm not responsible if your device is a brick afterwards

It's possible that the device will just boot up like it normally would have. I, personally, have had it happen that an update got "stuck" where it should have rebooted on its own and didn't.

If it doesn't come back up, you may then be forced to do a factory reset or reflash the original firmware using Odin.

A factory reset just requires booting into the recovery mode and selecting the "Factory Reset" option. To enter the Recovery mode, power the phone off completely, then press and hold Volume Up + Home + Power all at the same time. This will take two hands, so be prepared for that. Release all 3 buttons as soon as the screen flickers on, or holding the power button will force the device to power off again. The Recovery Mode screen should appear within a few seconds. NOTE: doing a factory reset is going to delete all your apps and data that is stored on the device's internal storage.

If it still won't boot up after performing a factory reset, it's time to try Odin. Doing so isn't super difficult, but it is too involved to list step-by-step here. Just google "galaxy s5 unroot". I know you're not trying to unroot, but you will find a guide on how to restore your S5 back to fresh-from-the-factory condition, which is what you are trying to do.