NetBoot


NetBoot was a technology from Apple which enabled Macs with capable firmware to boot from a network, rather than a local hard disk or optical disc drive. NetBoot is a derived work from the Bootstrap Protocol, and is similar in concept to the Preboot Execution Environment. The technology was announced as a part of the original version of Mac OS X Server at Macworld Expo on 5 January 1999. NetBoot has continued to be a core systems management technology for Apple, and has been adapted to support modern Mac Intel machines. NetBoot, USB, and FireWire are some of the external volume options for Mac OS re-install.

Process

A disk image with a copy of macOS, macOS Server, Mac OS 9, or Mac OS 8 is created using System Image Utility and is stored on a server, typically macOS Server. Clients receive this image across a network using many popular protocols including: HTTPS, AFP, TFTP, NFS, and multicast Apple Software Restore. Server-side NetBoot image can boot entire machines, although NetBoot is more commonly used for operating system and software deployment, somewhat similar to Norton Ghost.
To NetBoot a client machine, hold the "N" key as the Mac boots, or select the NetBoot server using the Startup Disk preference pane or control panel. Alternatively, New World Macs can be started with the Command, Option, O and F keys pressed to enter the Open Firmware prompt. Once in the Open Firmware one can tell the client to attempt the NetBoot procedure by entering "boot enet:0" and pressing the return key.
Client machines first request network configuration information through DHCP, then a list of boot images and servers with BSDP and then proceed to download images with protocols mentioned above.
Both Intel and PowerPC-based servers can serve images for Intel and PowerPC-based clients.

NetInstall

NetInstall is a similar feature of macOS Server which utilizes NetBoot and ASR to deliver installation images to network clients. Like NetBoot, NetInstall images can be created using the System Image Utility. NetInstall performs a function for macOS similar to Windows Deployment Services for Microsoft clients, which depend on the Preboot Execution Environment.

Legacy

Mac OS 8.5 and Mac OS 9 use only BOOTP/DHCP to get IP information, followed by a TFTP transfer of the Mac OS ROM file. Next, two volumes are mounted via AppleTalk over TCP on which the client disk images reside. All in all, the Classic Mac OS uses three images; a System image which contains the operating system and may contain applications. Next a private image is mounted in an overlay over the read-only System image. Finally, an applications image is mounted. This image, however, may be empty.