Configure an external NetRestore volume workflow
You can create a bootable volume on an external storage device that contains Disk Utility, Firmware Password Utility, Restore from Backup, Network Utility, and Terminal. This bootable volume can also be used to install macOS disk images using the Apple Software Restore (asr) command. The network image (the .nbi folder) created by System Image Utility should be stored on the external volume using Save As in the Create Image action.
Open System Image Utility for me
Click the Customize button in the choose a source window of System Image Utility to open Automator.
Select the System actions from the Actions column.
Select the Define NetRestore Source action in the Automator Library, then drag it in the workflow area.
Click the Add button
, then enter the location of your disk image and a description of the image.Select the appropriate checkboxes to specify how the disk image will be obtained.
Select the Create Image action in the Automator Library, drag it in the workflow area below the Define NetRestore Source action, then read the macOS License Agreement. If you agree, click Agree to continue.
Select NetRestore and, if necessary, select Include macOS Recovery partition.
Select a location to save the NetRestore network image, then name the image.
Enter both the network disk name and a description.
Select the Bless NetBoot Folder action in the Automator Library, then drag it below the Create Image action in your workflow.
Important: The Bless NetBoot Image Folder action should be the last action in the workflow, so it blesses the network image (the .nbi folder), not the disk image contained within.
Select a custom label and icon, if desired.
Click Save, then click Run.
To create a deployment image with a recovery partition, see the Apple Support article Creating a software deployment image with a recovery partition.