Thick imaging, thin imaging, and no imaging macOS

Last year, Tech Republic published a quick rundown on three approaches to Mac deployment.

Thought I'd do my quick take on it, based on my experiences.

Thick Imaging

Among the leading Mac admins out there (the ones giving workshops at conferences and on the tech panels and the primary contributors to widely used GitHub projects that facilitate Mac admin'ing), it seems there's something approaching a consensus that the admins should be moving away from the "golden master image" approach.

The idea of the "golden master" is that you have a Mac entirely configured exactly the way you want it and then image that to other machines, so they're completely identical.

In terms of the details of the imaging process, I have a tutorial here: Cloning an image using Thunderbolt and Disk Utility (post–El Capitan).


  • The imaging process itself is very quick per machine. One of our fully configured faculty laptops we can ASR over Thunderbolt in 3-5 minutes.
  • Takes up less bandwidth. We're actually blessed with some hefty bandwidth here, but your organization may not be, and imaging over Thunderbolt or even USB-3.0 would be a great way to not have the imaging process take forever or steal bandwidth away from your users.


  • If you build your "golden master" on an older Mac model and then try to image that over to a newer Mac model, you may get a do-not-enter sign when you boot up the newly imaged machine. So you'll always want to create the "golden master" on the newest Mac that you have.
  • You'll have to constantly update the "golden master" so that it doesn't quickly become a "silver master" or a "bronze master." At a certain point, if the source image is behind enough in updates, you'll be pulling so many updates post-image that you're not gaining any of the bandwidth reduction or speed-of-deployment benefits that you should get with this method.
  • If you have several different configurations, you have to create and maintain all of those different "golden master" images. So if you have a multimedia lab image and a faculty laptop image and a staff laptop image and a faculty desktop image and a staff desktop image and a library desktop image... that's a lot of separate images to create and maintain.

Thin Imaging

Historically, Mac admins have tended to favor DeployStudio for thin imaging over a network, but many Mac admins are eschewing Mac servers for Linux ones, so there's been increasing adoption of Imagr (which can be run on a Mac but also on Linux) instead.

If you want to set Imagr up on Linux, Getting started with BSDPy on Docker is a good place to start.

If you want to set up Imagr using OS X Server on a Mac, Amsys has a great step-by-step tutorial on how to do so: Part 1, Part 2, Part 3, and Part 4.

Whether you decide to go with DeployStudio, Imagr, or even a local Thunderbolt ("bronze master"), you'll probably want to look into using AutoDMG to create that thin, never-booted Mac image. Here's an example workflow using AutoDMG and Munki: AutoDMG / Outset / Munki bootstrap workflow.


  • Allows for flexibility in creating various workflows.
  • Since the thin image is never-booted, it will work with more hardware models (anything that supports the operating system version).


  • Requires a lot of infrastructure setup, particularly if you're using DeployStudio or Imagr.
  • Requires a lot of bandwidth (may be a non-issue at your organization).
  • May require netboot troubleshooting for particular laptop models or certain cables/adapters.
  • Netboot itself could take a while. And even if you're using AutoDMG over Thunderbolt, all the bootstrapped updates will pull over the network, so if you want to immediately deploy the machine, your user may end up waiting for a while for it to be fully usable.

No Imaging

"BUILDING" 2015 MACS describes a cool process of installing .pkg files over to a never-booted and non-imaged Mac over Thunderbolt and Target Disk Mode. Unfortunately, this appears to result in a slow booting or refusing-to-boot machine. Greg Neagle's (author of the aforementioned blog post and primary developer on Munki) workaround at the time was to boot into recovery mode and use the terminal to install the .pkg files. I believe he's eventually gone on to use Imagr instead, but the no-image concept is a good one to consider still.

One way you can do it without recovery mode is to have an external drive (with Thunderbolt or USB-3.0) that has a version of macOS installed on it with an autologin account and then install the .pkg files you need to get things up and running (/var/db/.AppleSetupDone, Munki, Munki bootstrap, etc.). It'll be quicker to boot than recovery mode.


  • You don't have to create an image, even a thin one (which, with AutoDMG, has to be built on the same exact version of macOS as the never-booted image you're using to build the image). You just need the packages you want to install.
  • The no-image boot is a lot faster than a netboot and comparable to a "golden master" image in speed to get done (sans updates) and move on to the next image.


  • Still consumes a bunch of bandwidth to pull all updates.
  • Requires a lot of booting to recovery mode (which takes a long time) or having a bunch of external drives to boot from (installing the packages over Thunderbolt and Target Disk Mode does not always work well).

Cloning an image using Thunderbolt and Disk Utility (post–El Capitan)

I have a longer post on this, including why you would want to clone using Thunderbolt and Disk Utility, but Apple decided to switch up Disk Utility's interface completely in El Capitan (10.11). Even though the process is similar, the exact steps are different.

One procedural difference worth noting: In Yosemite (10.10), Mavericks (10.9), etc., you would select the source, and then select what you wanted to restore the source to. In El Capitan (10.11) and supposedly beyond, you start by selecting the destination, and then select what source you want to restore from.

diskutilityrestoreelcapitan01 Open up Disk Utility (from /Applications/Utilities). Select the disk you want to restore to. And then select Edit > Restore.

diskutilityrestoreelcapitan02 You have the option to restore from another disk (if you have a computer connected via Thunderbolt, it should show up in the drop-down list) or to restore from a disk image (click Image... to find the image you want to restore from), and then click Restore.

diskutilityrestoreelcapitan03 Wait for it to restore.

diskutilityrestoreelcapitan04 Click Done when it's done restoring.

Cloning an image using Thunderbolt and Disk Utility

Why would you do this?

  • It's fast. Over Thunderbolt, cloning a roughly 30 GB (of used space) image takes only a few minutes.
  • Minimal additional cost. Sure, you probably paid money for your Macs, but this method uses only included software... and one US$40 cable.
  • No external media or extra setup. You don't have to network your computer, install additional software, or have an external hard drive. You can go straight from computer to computer with just a Thunderbolt cable.


  • Two Macs—one source, one target.
  • Rename the hard drive on the source Mac to something unique (don't call it Macintosh HD, which is the default). Easiest way to do this is to go to Finder > Preferences and then check or tick Hard Disks under Show these items on the desktop. Then, when you see the hard drive icon appear on your desktop, you can rename it.
  • A Thunderbolt cable.
  • The main hard drive partition of the source Mac must be equal to or lesser in size than the target Mac hard drive. For example, if you are imaging from 250 GB to 250 GB, that's okay; if you're imaging from 250 GB to 500 GB, that's also okay; but if you're imaging from 1 TB to 500 GB, that won't work.


Note: If you're using El Capitan (10.11) or later, the procedure has changed. More details at Cloning an image using Thunderbolt and Disk Utility (post–El Capitan)

The procedure below is for Yosemite (10.10) and earlier.

  1. lightningboltOn the target Mac, reboot the computer while holding down the T key on the keyboard to boot it into Target Disk mode. If you have done so successfully, you will see what appears to be a white lightning bolt on the screen.
  2. On the source Mac, reboot the computer while holding down the Cmd and R keys on the keyboard to boot into Recovery Mode.
  3. Then, connect the Thunderbolt cable to both Macs.
  4. On the source Mac, select Disk Utility from the available options.
  5. diskutility
    Once Disk Utility launches up, click on the main partition (the one you renamed earlier) of the source Mac. Since Disk Utility can sometimes load up the target Mac visibly higher or lower than the source Mac, it's critical that you have them uniquely named (that's why we renamed the drive earlier). So click on that unique name.
  6. Click Restore. You should see the source as the uniquely-named drive.
  7. Then drag the main partition of the target Mac over to the Destination area.
  8. Click Restore.
  9. That's it! Once it's done, you can boot your target Mac into regular mode, and it should be a clone of your source Mac.