Network booting
From Wikipedia, the free encyclopedia
Network booting is the process of booting a computer from a network rather than a local drive. This method of booting can be used by routers, diskless workstations and centrally managed computers such as public computers at libraries and schools. Network booting can be used to centralise management of disk storage, which supporters claim can result in reduced capital and maintenance costs. It can also be used in cluster computing, in which nodes may not have local disks.
The initial software to be loaded is loaded from a server on the network; for TCP/IP networks this is usually done using the Trivial File Transfer Protocol. The server from which to load the initial software is usually found by broadcasting or multicasting a Bootstrap Protocol or Dynamic Host Configuration Protocol request. Typically, this initial software is not a full image of the operating system to be loaded, but just part of it - enough for the operating system to start and then take control of the booting process, and continue booting over the network.
Before IP became the only Layer 3 protocol, NetWare Core Protocol and IBM RIPL was widely used for network booting. Their client implementations also fit into smaller ROM than PXE. Technically network booting can be implemented over any of file transfer or resource sharing protocols, for example, NFS is preferred by BSD variants.
Network booting is also used for unattended operating system installations. In this case, a network-booted helper operating system is used as a platform to execute the script-driven, unattended installation of the intended operating system on the target machine.
Contemporary desktop PCs often provide an option to boot from the network in the BIOS. If this option is not available - as is the case on many PCs from the 1990s - a floppy disk or USB flash drive containing software to boot from the network may be used instead, or a ROM chip can be physically installed on the network card. For example, Rom-O-Matic from the Etherboot project can generate either ROM images or floppy boot images for many different network cards. The small piece of code generated by Rom-O-Matic does not contain any operating system as such - merely the bare minimum of code needed to initiate a network boot.
