Step 1 – Grab The SD Card
Power down the Pi and remove the SD card. Insert it into your PC.
Step 2 – Edit cmdline.txt
The boot partition should be visible and contain a file named “cmdline.txt”. Edit this file in a text editor and add the following to the end of the existing text :
If the original content was :
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
it should now look like :
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait init=/bin/sh
Make sure it is all one line! Save the text file and eject the SD card from the PC.
Step 3 – Reset the Password
Insert the card into a Pi that is connected to a monitor and keyboard. Power up the Pi. There may be a delay but you should be presented with a flashing cursor.
At the prompt type the following command :
You will then be prompted for a new password. Enter it carefully and press the [Return] key. It will now ask you to retype the password.
The password has been changed.
Now type the following commands :
The Pi will continue to boot and return you to the normal command line prompt.
Shutdown the Pi and power it off.
Step 4 – Edit cmdline.txt
Using the PC edit the “cmdline.txt” file again and remove the “init=/bin/sh” text you added in Step 2.
You can now return the SD card to your Pi, reboot and use the new password.