Overview
PXE is an industry standard that enables computers to boot and be imaged over the network. Instead of booting from CD/DVD or USB drive, a computer loads an image over the network into the computer's memory.
Technical Explanation
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(from the Landesk Users Guide)
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PXE (Preboot Execution Environment) is a networking protocol that enables
devices to be booted and imaged from the network, by downloading and installing an
executable image file from an image server, before the device boots from the local hard drive.
On a PXE-enabled device, the PXE protocol is loaded from either the network adapter's flash
memory or ROM, or from the system BIOS.
PXE uses the following communication standards: DHCP (Dynamic Host Configuration
Protocol), TFTP (Trivial File Transfer Protocol), and MTFTP (Multicast Trivial File Transfer
Protocol).
When a PXE-enabled device boots up, it sends out a DHCP discovery request. If a DHCP server
implementing PXE is found, the server assigns an IP address to the device and sends
information about available PXE boot servers. After completing the DHCP discovery process,
the device contacts the PXE server and downloads an image file through TFTP. The imaging
script is then executed, loading the OS image from the imaging server onto the device. The
image file is referenced by an OS deployment script.
If you want to learn more about PXE and its underlying technologies and functionality, read
the PXE Specification v2.1 located at http://download.intel.com/design/archives/wfm/downloads/pxespec.pdf.