Most Linux hosts have only one user with root privileges, so you need to reset the root account password via a different path. The easiest path is to reset the root password by changing the grub boot parameters into single-user mode at boot time.
The first step is to restart the host, press ESC to select the operating system to enter, and then press the E key to enter edit mode.
The second step is to navigate to a line beginning with kernel and press E to add a "single" Start-up parameter at the end of the row, indicating that you want to enter into one-user mode.
After the third step press ENTER to confirm, press the B key to boot the system into single user mode, directly into the shell environment.
The fourth step is to reset the root user's password by executing the "passwd root" command in a single-user shell environment, and enter the "reboot" command to restart the system.
Linux Forgotten root Password
