Root Password in centos

when cenos is installed on a VM several times, no prompt is displayed for entering the root password. The root account cannot be used, I used to think it was a problem with the virtual machine version. There are still some problems with virtual machines with several versions. Today, using the methods provided on the Internet, we have finally cracked the root password problem.
the procedure is as follows:

1. at startup, after entering the startup interface, press any key except the Enter key to enter the interface. Then press E " key to enter the centos startup interface

2. press E to enter the centos startup interface, move the cursor to the "kernel" configuration item line

3. press E to edit the "kernel" menu item, and enter Single ( do not delete it. Enter a space at the end of the row, and then enter single ), to tell the Linux kernel that the subsequent startup process needs to enter the single-user mode. After the change, press enter to return to the centos Startup menu item interface, and then press B " uses the changed centos boot menu item to start single-user mode.

4. after the system is started, it runs in single user mode. Enter passwd to change your root user name, enter it twice, and then Reboot the system will restart after a while. That is, you can change the root password to log on to the system.