The answer is not complete, I rearrange the solution is seen on other sites.
For VMware's forgotten password in CentOS, here's the solution:
Start the system, press the ESC key above the keyboard before entering the system, enter the following interface
2. Press the E key on the keyboard to display the following interface
3. Select the second entry kernal, press the E key, the following interface appears
4. Make a space, enter the number 1, return to the interface
5. Locate in the second item, press the keyboard B key, the system will restart automatically, enter the following interface
6. Enter passwd root, enter the new password, return, and then lose again
See Passwd:all Authentication tokens updated successfully. Line
Description Password Modified successfully
7. Enter Shutdown-r now to enter and restart the system.
Enter root and enter the password
You can have it.
Oracle VM VirtualBox centos6.3 installed, but forgot how to change the account password at startup