asr or Apple Software Restore is a command line utility in Mac OS X used to apply a DMG disk image to a selected volume or mount point on a file system. It is often used for cloning large numbers of Macintosh computers. Apple Software Restore can read an image locally or from a server via HTTP or its own multicast asr:// URI.
asr has two methods it can use to restore an image to a volume: it can either copy items in a file-by-file mode, or it can copy the image as a (optionally compressed) stream of bytes. As the latter method does not need to go through a complicated filesystem it is much faster, typically being limited only by the speeds of the drives or network connections involved. But in order to use this faster method the dmg involved must be checksummed, and in some cases the files re-ordered inside the image. This is also done by the same binary.
The graphical Disk Utility uses asr processes in the background to perform restores.
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