PXE
PXE (Preboot Execution Environment) boot is a network-based booting method that allows a computer to load an operating system or other software directly from a network server, bypassing the need for local storage. PXE boot is commonly used in environments where centralized OS deployment, maintenance, or diskless workstations are necessary, such as data centers or corporate networks.
How PXE Boot Works
PXE boot uses a combination of network protocols (primarily DHCP and TFTP) to facilitate the boot process. Here’s a step-by-step breakdown of how it works:
1. Network Interface Check: When a PXE-enabled system starts, it looks for a network card with PXE capabilities (most modern NICs support PXE).
2. DHCP Discovery: The system sends a DHCP (Dynamic Host Configuration Protocol) request to locate a PXE server. The request asks for an IP address and indicates that it’s a PXE boot request. A PXE-compatible DHCP server responds by providing:
• An IP address for the client machine.
• The location of the PXE boot server.
• The name and path of the initial boot file (usually a small executable or kernel).
3. TFTP Boot File Download: Using TFTP (Trivial File Transfer Protocol), the client then downloads the specified boot file from the PXE server. This boot file is typically a small program that initializes the hardware and prepares the system to load the full operating system image or installer.
4. Loading the OS or Deployment Image:
• The downloaded boot file usually loads a minimal operating environment (such as a Linux kernel or WinPE environment) into memory.
• This minimal OS environment then mounts a network share or makes further requests to download the main OS image or installer files, which are typically hosted on the network server.
5. Booting the OS: Once the OS image is fully loaded, it boots up, either running directly from memory (for diskless setups) or installing onto a local disk if the machine is being provisioned.
Example: Deploying an OS via PXE
For a scenario where you need to install an OS on multiple machines in a data center:
1. Configure a PXE server to store the OS images, along with DHCP and TFTP services.
2. Configure each client machine’s BIOS/UEFI to boot from the network.
3. On boot, each client sends a PXE request to the server, receives the boot file, loads the OS installer, and begins OS installation.
This makes it efficient to install or update operating systems across large numbers of machines simultaneously.
Common Use Cases for PXE Boot
• Diskless Workstations: Computers boot entirely from the network without any local storage, saving on hardware costs and enabling centralized management.
• OS Deployment and Provisioning: Quickly install or update OS on multiple machines, commonly used for automated OS installations in data centers.
• Remote Troubleshooting and Recovery: PXE allows administrators to boot into recovery or diagnostic tools without needing physical access to the machine or a local OS.PXE Boot Advantages
• Scalability: Supports deploying OS and software across large numbers of devices simultaneously.
• Centralized Management: Software images are stored on a central server, making updates or changes easy to manage.
• Hardware Savings: Diskless workstations can be set up using PXE, reducing the need for local storage.PXE Boot Requirements
1. PXE-compatible Network Card: The client machine’s network card must support PXE.
2. PXE Server: A PXE server to provide DHCP and TFTP services and to store OS images.
3. Network Configuration: A stable and high-bandwidth network is ideal, especially for large deployments.PXE boot simplifies management by centralizing OS deployment and system maintenance, making it invaluable in environments with large numbers of networked devices.