This article describes why a VDOM cannot be deleted.
Scope
All FortiOS.
Solution
When a VDOM is created, there are two references by default. Once switching to the VDOM, a few items under the Dashboard are generated automatically, as shown below:
These items correspond to the CLI config of ‘config gui-dashboard’ under ‘config system admin’:
However, this config is not visible while running the command ‘show’ or even ‘show full-configuration’.
With this hidden config, it might not be possible to delete the references even though it shows the VDOM is referenced by related admin users.
In such a scenario, deleting the config under ‘config gui-dashboard’ is necessary:
As long as the ‘System Administrator’ references are deleted, the VDOM ‘Delete’ button is not greyed out anymore.