After the password is changed, it is not used in the next time, I forgot ~~~ FAINT
So the hard drive forgot the password is hung on the system with root privileges.
First check the file system #fsck -y / dev / ad2s1 mounted to a directory
#mount / dev / ad2s1 / mNT Create an environment with Chroot
#Chroot / MNT then mount the USR directory that loses the ROOT password
#fsck -y / dev / ad2s1f #mount / dev / ad2s1f / mnt setting password
# / usr / sbin / passwd root setting, save the hard disk back to the original machine.
Landing normal.
Restart FreeBSD, press any key (except Enter) when inverting, then enter 'boot -s', enter the system and run the `# / sbin / mount -a`, now you can use` passwd` Modify the root password
