Apple Software Restore

Apple Software Restore (ASR or asr) is a command line utility from Apple that can be accessed through Terminal in Mac OS X or macOS. It can be used to apply a DMG disk image file to a partition or volume in a file system. ASR can read an image locally or can be used for mass deployment of many Macintosh computers that are cloned from a server.

Functionality
ASR can restore from a disk image through a file-by-file mode, or it can directly block-copy the image. The latter method bypasses the filesystem and is faster, but requires that the disk image first be checksummed. The Disk Utility application that is bundled with Mac OS X / macOS uses ASR to perform restores through a graphical user interface.

History
Apple Software Restore previously existed as a classic Mac OS application that was included with Mac OS 8.5 or later.

During the 2019 Worldwide Developers Conference, Apple suggested that developers use ASR instead of third party applications for backups of APFS volumes. In macOS 10.15.5, third-party applications that did not call ASR were no longer able to create bootable backups of volumes running macOS Catalina.