The root account will lock After three incorrect login attempts for 15 minutes.
To unlock the root account without wait 15 min you can use below steps :
4. Press F10 to start the boot process. The system will boot to a bash shell.
5. Unlock the root account by running command: pam_tally2 –reset –user root.
6. Reboot the appliance by running command: reboot -f.
Try to connect to vCD cell (Web or SSH) using root account.
Note: This process supported with vCD 9.x and 10.x