Firepower FMC admin password reset

 Firepower FMC GUI admin password reset

root@FMC74:~# sudo usertool.pl -p 'admin new_pass'

root@FMC74:~# sudo usertool.pl -r admin                            

   Then login GUI with current password will be prompt to change password

 Firepower FMC CLI admin password reset

reboot FMC

when see red box, press space to abort boot process

at "boot:" prompt, enter FMC version and "single, for example: 

boot: 7.2.5 single

Then 

passwd admin << may see BAD PASSWORD messages, info only, ignore it.

reboot