#420 add info on how to reset SSH certs

FAQ.md

@@ -914,4 +914,19 @@ When the LCD display is telling you to do config check:
 
 ## How to fix my upside down LCD after update?
 
-Some displays have a different orientation. To fix this activate/deactivate the LCD-ROTATION option in the MAINMENU > SERVICES and let it reboot. YOu might need to do this up to 3 times until your display got it right.
+Some displays have a different orientation. To fix this activate/deactivate the LCD-ROTATION option in the MAINMENU > SERVICES and let it reboot. YOu might need to do this up to 3 times until your display got it right.
+
+## How can I repair my SSH login?
+
+If you cannot login per SSH into your RaspiBlitz your SSH RaspiBlitz certs might be corrupted. To renew and reset those do the following:
+
+- shutdown the RaspiBlitz - if you dont have touchscreen activated, disconnect LAN cable, wait until HDD/SSD activity slows down (no constant blinking) and then cut the power
+- take out the sd card and connect it to your laptop - it should appear as a `boot` drive
+- in the root directory of that `boot` drive create a file called `ssh.reset`
+- that file can be empty or just copy another file on that drive and rename it ()
+- eject the drive from your laptop safely
+- put sd card back into the RaspiBlitz (also make sure LAN cable is connected again)
+- power up - the RaspiBlitz should boot up & reboot again
+- then try again to SSH login
+
+If you see a "REMOTE HOST IDENTIFICATION HAS CHANGED!" warning on login thats what we wanted - the SSH cert of your RaspiBlitz changed - thats good. We just need to remove the old one from our laptop first - on OSX you can use `rm ~/.ssh/known_hosts` (deletes all cached server certs) or remove the line with your RaspiBlitz IP manually from the `~/.ssh/known_hosts` file with a text editor.