AutoCasperNBI 101: Restorable DMGs

So let's say you're in an environment where there are too many hoops to jump through to set up a NetBoot. Or you simply don't have the pieces in place to make one work. Did you know that AutoCasperNBI can generate a restorable DMG that you can use to make a boot disk on an external drive or USB?

Fun fact: it can.

Another fun fact: using AutoCasperNBI to do this is way better than building it out from scratch.

Here's how it works.


- A Mac (VM or otherwise) running the most recent version of macOS
- AutoDMG
- AutoCasperNBI
- A copy of Casper
- A fast read/write speed external drive or USB stick (my recommendation)

Building the base OS installer with AutoDMG

AutoCasperNBI requires an OS installer built with AutoDMG, so we'll start with building that OS installer.

1. On a VM or other available Mac, download the latest version of the macOS installer app from the App Store.

2. Open AutoDMG and drag the OS installer into the drop area.

3. AutoDMG will check for available updates, and allow you to download them to include in the OS installer you're about to build.

4. Once the updates are downloaded (if needed), Build the OS installer.

AutoDMG will finish building the OS installer, with the progress visible in the dialog that appears. You can also follow along in the log.

5. Locate the OS installer just built. This is the OS.dmg you'll need to make your Restorable disk image.

Building a Restorable DMG with AutoCasperNBI

1. Open AutoCasperNBI. Select the OS.dmg that was just built with AutoDMG, then select the Casper that matches the major version of your JSS.

2. In the JSS URL, enter the URL of your JSS.

3. Set a NetBoot name if you want (or use the default), then click the Options button to look at the additional settings needed for the disk image.

4. In the Advanced tab, set a local ntp (time server) and time zone. Check the Create a Restorable DMG checkbox.

5. Once these preferences are set, close the Options dialog and Build the NetBoot image. Authenticate using local admin credentials when prompted, and select a place to save the image. It will then start building.

6. When complete, a restorable dmg (disk image) will be saved on the machine.

7. Now, plug in the USB or external drive you want to use for imaging. Open Disk Utility.

8. Erase the drive and rename it something memorable.

9. Click on the primary partition of the external drive and click the Restore button. You'll be asked to select a disk image to use for the restore. Find the Restorable DMG you created with AutoCasperNBI and choose it as the restore image.

10. Click the Restore button and Disk Utility will take the contents of the Restorable dmg and put it on the external drive.

11. When complete, the drive is ready to use for imaging.

12. Unmount the drive. It's now ready to use.

Using the external drive for imaging

1. On the machine your want to image, plug in power, an ethernet cable (or cable and appropriate adapter), and the boot disk.

2. Power on the machine, holding down the Option key.

3. A boot menu will appear, select the NetBoot image you just created and hit Enter.

4. The machine will then boot into the disk you just built and start up an OS and load Casper Imaging. You can then complete the imaging process.

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