Reset the root password from the boot process.

Solution:

Reboot the system.

Interrupt GRUB boot.

Press e to edit the boot entry.

On the linux line, append:

rd.break

Boot with Ctrl+x.

At the emergency shell:

mount -o remount,rw /sysroot

chroot /sysroot

passwd root

touch /.autorelabel

exit

exit

Detailed Explanation:

rd.break drops you into an early emergency environment.

/sysroot contains the real root filesystem.

mount -o remount,rw /sysroot makes it writable.

chroot /sysroot changes into the installed system.

passwd root resets the password.

touch /.autorelabel is critical so SELinux relabels files on next boot.