1. Sign in to the vSphere client and select your VMware vCenter.
2. Select the Admin virtual machine for your system.
3. Open the virtual machine console window.
4. Power on the Admin virtual machine.
5. Once the virtual machine boots and you see the splash screen, then select the Ctrl + Alt + Backspace keys to get to the command-line prompt.
6. Select the Restart Guest button.
7. Select Yes to confirm the reboot. Quickly click the mouse in the console window (the black area) to set the keyboard focus to the virtual machine console. Quickly press "any key" and continue to press it about once every second, to get to the GNU GRUB boot loader menu. After a minute or two, you will see the following message: Booting Cent 0S (<string_numbers_letters>) in <number> seconds...
8. Press any key once more to interrupt the boot process and display the GNU GRUB boot loader menu.
9. Press e to edit the commands before booting the virtual machine.
10. Press the down arrow key to select the "kernel" line then press e to edit this kernel line.
11. Enter single.
12. Press the Enter key to save your changes and return to the previous menu.
13. Press b to boot into single user mode.
14. Once the virtual machine boots and you see the splash screen, then select the Ctrl + Alt + Backspace keys to get to the command-line prompt.
Cisco TAC will provide you with the root credentials and further instructions. Once you complete your tasks, enter reboot or select the Restart Guest button in the virtual machine console window.