When installing the vCenter Server Appliance on a single ESXi server, you might find yourself locked out of the host’s web interface. Attempts of logging into the root account for ESXi will return a “Permission to perform this operation was denied” error.

The issue is that the installation process puts the ESXi host into Lockout Mode, which prevents you from logging into it directly using the web interface. If you fail to configure the vCenter VM to autostart, you won’t be able to acess the server configuration via the appliance either.

Luckily the solution is pretty simple, but you will need to connect a monitor to the server itself, and manage the configuration from the Direct Console User Interface (DCUI):

1. Press F2 to enter the System Customization screen
2. Select Configure Lockdown Mode
3. Press Space to deselect the “Enable lockdown mode” option

Now you’ll be able to log in directly to the ESXi host again, no need to reboot. Don’t forget to enable autostart for the vCenter appliance VM!