Forgot root password

My workmate forgot his root password. Fortunately, the rootfs is stored in SD card. So he unplug it and mount it in the PC environment. To reset the root password, we can edit the /etc/shadow file. In that file, there is a line like:

root:x3FrTg6uYT7.:0:0:root:/:/bin/sh 

Just remove the password in the second field:

root::0:0:root:/:/bin/sh 

That's done!