The more currently installed Vcenter Server Appliance 6.5 customers, the more often the default root password policy is ignored during the configuration process for the user: 60 days expire. Once the password expires or forgets the password, the VCSA Admin console will not be able to log in by Root.
The following is a reference to the official KB method to modify the forgotten or expired root password.
1. Please make a copy of the VCenter Server Appliance 6.5 Snapshot or backup before continuing. Do not skip this step.
2. Re-boot VCenter Server Appliance 6.5.
3. After the operating system starts, select the option e key immediately to enter the GNU GRUB Edit menu.
4. Find the line that starts with the word Linux
5. Append the following entry to the end of the line:?? RW Init=/bin/bash?? The line should look similar to the following screen
6. Press F10 to continue booting
7. At the command prompt, enter the command passwd and provide a new root password (enter two times to confirm):
passwd
8. Unmount the file system by running the following command:
umount/
9. Run the following command to re-boot VCenter Server Appliance 6.5:
Reboot-f
10. Confirm that you can access VCenter Server Appliance 6.5 with the new root password.
11. Remove the snapshot created in step 1, if applicable.
VCSA vCenter6.5 Reset Retrieve root password