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I have a NetBoot server to manage all the Macs in my office. However, when I started a weekly backup of one of my iMacs last week, after rebooting and holding N, I saw the blinking globe for a few moments and then the system booted from the hard disk.

As far as I know, no configuration changes have been made to the NetBoot server. Other iMacs still can netboot fine.

This particular iMac had the iMac EFI Update 1.7 installed whereas none of the other Macs have. I suspect that is the culprit especially given Apple's description:

This update enables Lion Recovery from an Internet connection [...]

Does the iMac EFI Update 1.7 change how NetBooting works? If so, how specifically? Does the vendor-class-identifier of the DHCP request change?

(I'm happy to edit the question with additional details about my configuration if it will help)

UPDATE: I confirmed that the vendor-class-identifier in the DHCP request did not change after this update:

DHCP Request

And indeed, the server is sending back the proper booter filename and image path:

DHCP Response

So there's something else at play here...

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Yup they broke it. Early Internet recovery firmware versions don't netboot. later versions fixed this.

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