Today to say is reset centOS administrator password.
When forget the root user's password, you can not log on Linux systems to perform administrative and maintenance tasks, and can only log on using some restricted features by other users. However, most Linux host user with root privileges only one, and therefore need other ways to re-root account password reset. The easiest way is to grub in the boot by boot into single-user mode parameters, using a rescue mode is another way.
The explanation herein is a method of rescue mode
Procedure
1, the loading system image
2, Change Password
Practical parts
1, restart the virtual machine, when you see the progress of the reading time by pressing the Esc (step menu and repair as grub), press "1" to enter a simple mirror mode 
2, input chroot / mnt / sysimage, mirroring system loading, into bash mode, enter psswd root to change the password, exit to exit bash mode, reboot restart just fine.