Back to Linux …

 It's very simple method how to do it

 Boot into grub, select single user but do not press enter.
 Press e to go into edit mode.
 Scroll down to the kernel line you will boot from, it starts with "linux /boot/vmlinuz-……."
 Scroll to the end of that line and press space key once and type init=/bin/bash
 Press Ctrl X to boot

 # Remount / as Read/Write
 mount -rw -o remount /
 # Change the root account password with
 passwd
 # Change any other account password with
 passwd username
 # type new password, confirm and hit enter and then reboot.