1. Reboot the system
2. When you see the Grub menu, highlight your Fedora installation with the arrow keys and press ‘e’ to edit.
3. Again use the arrow keys to highlight the line saying ‘kernel’ at the beginning and press ‘e’ again, which will let you edit that line.
4. Append a space at the end of the line and type ’single’ without the quotes there. Press the Enter key.
5. Now press ‘b’ which will take you to the Linux single user mode where you’ll have privileged access without typing a password.
6. Now you do a passwd, and change your root password. Then reboot. You are done.
Now enter into TTY mode and login as root and use passwd "username" to change the password of needed password