The below is to try explain the use of the Enabled/Disabled Identifiers arrays in the NBImageInfo.plist on OSX Server.

This is to try & better explain their use.

How are they arrays generated?

NBI’s that are generated via SIU have a NBImageInfo.plist which is populated from the SupportedModelProperties array in /System/Library/CoreServices/PlatformSupport.plist.

DisabledSystemIdentifiers

That array then populates the “DisabledSystemIdentifiers” array in NBImageInfo.plist like the below:

This allows you in OSX Server.app to select the models to restrict booting to the NBI:

If this Array is empty then no restrictions can be made:

EnabledSystemIdentifiers

With the “EnabledSystemIdentifiers” array populated, access is restricted on the NBI, to only those System ID’s that are in the array.

This then shows in Server.app as the NetBoot Image as having “access restricted”

So the correct behaviour for any NetBoot Server is to whitelist based on entries in the ‘EnabledSystemIdentifiers’ array, in the same way as access is controlled based on entries in the “EnabledMACAddresses” array within NBImageInfo.plist.