iMac Pro Implications for Mac Admins

The first iMacs Pro will ship this week to some lucky buyers, just in time to keep Apple’s promise of shipping this year.

Now that we have all gotten over the sticker shock when you max out the configuration in the Store, what does the new tech in iMac Pro mean for admins?

Secure Boot

First is the new secure boot. iMac Pro comes with Secure Boot enabled and External Boot disabled. You can disable (or moderate) the settings in the new ‘Startup Security Utility’ in Recovery.

With secure boot enabled, a Mac will verify the integrity of the OS and confirm with Apple before booting. It may require an update to be installed before continuing to boot.

Somewhat surprisingly, Secure Boot on the iMac Pro will verify the integrity of a BootCamp/Windows installation as well as macOS. (The continued persistence of BootCamp makes me wonder what Apple uses it for internally.)

The support article seems to imply that on the strongest setting, the iMac Pro might force an update before you can boot. We will have to wait and see how far back Apple will “trust” older versions of macOS.

By default an iMac Pro will not boot from an external device. This setting can be changed in the ‘External Boot’ area of the Startup Security Utility.

You can still boot to the Startup Manager with the option key but when you select an external drive you will get an error message. You can only select internal drives with the option key.

Both of theses settings can probably only be disabled manually in Recovery mode. This renders most automated installation and imaging procedures useless. Also the support article states that you have to enter a local administrator password to change the setting. This can also be difficult in settings where a tech or admin might not know a local password.


Prohibiting External Boot will (probably) also prohibit NetBoot and NetInstall. However, Apple updated their support article “Create a NetBoot, NetInstall, or NetRestore image” with the note:

iMac Pro computers don’t support starting up from network volumes.

Also the support article “Mac startup key combinations” has added this to the description of the ‘N’ key:

iMac Pro doesn’t support this startup key.

It is as of yet unclear if this means that iMac Pro will not NetBoot under any circumstances or if it will NetBoot, but not in the default configuration and you have disable the boot security first.

The phrasing in the articles seems clear, but it may be an error/omission. If you happen to get your hands on an iMac Pro and can test, NetBoot/NetInstall, please let me (and everybody else) know.

The other question that remains is whether Internet Recovery still works on the iMac Pro. There has not (yet) been an amendment to the Internet Recovery support article. Internet Recovery is a form of NetInstall as well, albeit with a different discovery method.

Imaging is dead and NetInstall is not doing so well

So, as predicted, the iMac Pro puts yet another nail in the coffin of imaging. You will have to run the iMac Pro in a lowered security mode, for it to accept an OS that was not installed on itself and verified by the internal T2 system controller chip.

While it is still possible to disable the boot security, this has to be done manaully. There is no way to automate the deactivation, much like you cannot automate disabling SIP.

Finally, NetInstall might not work at all, even when the boot security is disabled. And even if NetInstall does still work on the iMac Pro, NetInstall is still quite broken in High Sierra: additional pkgs have to be in just the right format to work, automated installations are broken, and you cannot initiate a NetInstall remotely through a script or the management system, but have to be physically at the machine and hold the ‘N’ key. (all of these affect all Macs, not just the iMac Pro)

And even when you have managed to get all of these to work, then new security like UAKEL and UAMDM might still require an administrator to touch all the machines again after re-imaging.

“Zero-touch” deployment

When you consider the standard use case, where a Mac is in possession of a single user (whether it is owned by that user or organisation) then most of these problems are fairly easy to work around with some user guidance and education. DEP enforces enrollment and tools like SplashBuddy and DEPNotify can make the process more understandable for the user.

“Zero-touch” deployment in this case means that the IT department will not have to touch the device. Even though you can automate much of the configuration, the enrollment is not entirely automatic, the process still requires the user to be at the Mac and fill in or confirm some dialogs.

However, for other deployment scenarios, especially general access labs in education, this breaks exisiting workflows. You never know what the users (and applications) are going to do to a system, even if they don’t have adminstrative privileges. Re-imaging rather than figuring out which configuration is broken is a quick and efficient remediation for many problems.

Many professional software packages are notoriously hard to install in an automated fashion and even harder to de-install cleanly. In addition, this kind of software tends to have very strict licensing terms and high prices. “Wipe and re-install” is a simple and fast workflow to ensure software and drivers are removed cleanly and repurpose a Mac (or an entire Lab of Macs) for a different task. (e.g., switch a video or audio lab to an lab with engineering and math software) Many admins have fully automated touch free workflows that can be started remotely through ssh, Apple Remote Desktop or a management system.

Not only do all of these workflows have to be re-visited and re-built without imaging, but they will not be able to run without user interaction. Without NetInstall (or if NetInstall remains broken) the user interaction may be non-trivial.

To wipe and re-install an iMac Pro, an admin has to boot to Recovery, manually erase the drive in Disk Utility and then start the installation process. The tech or admin will have to know and enter a local administrator password. Even with DEP, there are a few dialogs after the installation that need to be confirmed manually before DEP and any automation from the management system can start their work.

True “Zero-touch”, where no-one has to physically touch the Mac, (re-)deployment is not possible with Apple’s currently supported toolset for High Sierra and iMac Pro.

The Missing Piece

If macOS had an “Erase All Content and Setting” option like iOS does, then you could do a quick reset and with DEP + management system quickly restore a Mac to the previous (or a new) configuration. On iOS this is achieved by keeping the system on a separate volume from apps and user data. This separation would not be quite so easy on macOS, but with APFS snapshots the system could create (and preserve) a snapshot after a clean installation and provide hooks for scripts and management systems to restore to that.

It is quite frustrating that this option does not yet exist. Apple is removing older workflows from the toolset without providing a functioning alternative. If Apple decides to implent this function in macOS and enable its automation from an MDM, then you have the best of both worlds, the advanced security and automation and management for admins!

Make Noise

Apple seems to be unware of or indifferent to these methods and workflows. Most enterprise customers might not be affected by them. Those customers that are, need to let Apple know through the usual means: your sales reps, your support contact (if you have one) and by filing bugs.

If you are at an instituition that is considering to buy a classroom full of iMacs Pro you will have a large financial leverage with this deal. So let your sales reps and engineers know of your issues, but also be understanding that they might not have a solution for you right away.

Even so, DEP and MDM will be a major part of whatever solution you will have to use in the future. If you have not started working on your implementation yet, there is no time like the present.

Maybe you can use this article to convince your management to purchase an iMac Pro so you can test it. If that actually works, let me know. 😉

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Mac Admin, Consultant, and Author

10 thoughts on “iMac Pro Implications for Mac Admins”

  1. Am I being dense or maybe blind, but is there no “About” page on this site? Who writes this site. Just curious really.

  2. I’m working with a demo iMac Pro, and it will not NetBoot at all. We’ve previously used a NetBoot volume for DeployStudio, so presumably I have to figure out how to get it to install on an APFS external drive. Of course operating with the theory that this is the new platform that Apple is going to roll with.

    1. NetBoot, NetInstall and other external deployment methods seem to be dead in the water with iMac Pro. The new alternativ workflows depend on your needs and goals but will probably be some combination of DEP, MDM, and management system (Jamf, Munki, etc.) and some manual steps (Recovery to clean install)

  3. We have just received our first iMac Pro. I’ve had time to play with it a bit, and even after turning off all the Startup Security settings, it won’t NetBoot.
    I’ve created specific .nbi’s for it, but nothing works. The images show in the Startup Disk pane, but not in the Boot Manager.
    The Recovery Drive seems viable, so OS restore + DEP + MDM shoulkd work (when we get it!), but DeployStudio + NetBoot is dead. DS + external drive does seem to work.

    1. One thing that our Apple rep mentioned as a concern was that an external drive created from the iMac Pro might be encrypted for that specific hardware and not bootable by another machine.

      If you, or anyone for that matter, gets a second iMac Pro, I’d be interested to see if that can be verified or debunked.

  4. Just an FYI – Technically they do netboot (diskless + Internet boot works). AST2 OS based repair tests are local netboot only and I have installed the netboot image on to 10.11 server, shared via nfs and requested a OS test on an iMac Pro. Voila – it reboots from this image. I have not explored why this would work and no other image will or what allows this to work as yet but it is not entirely precluded…

    1. Apologies –
      The netboot image share is via ‘http’ NOT ‘nfs’. Was typing on autopilot 😉

  5. DeployStudio will work with iMac Pro,
    It will no longer boot off network, but you can build a USB bootable drive, and link it to a network deploy studio server.

    build a work flow and point it to the image.
    If you use the restore and choose an image it will not work. you get a flashing folder as for some reason it doesn’t bless the system.

    1. But to enable external boot on an iMac Pro you have to fully install macOS because you need an admin password in recovery to unlock the external boot option. I don’t believe that’s a practical effort on a large scale

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