LWM-Linux/15 - Linux Distributions and Deployment/PXE Boot.md

PXE Boot

1. Introduction to PXE Boot

PXE (Preboot eXecution Environment) is a protocol that allows a computer to boot from a network interface independently of available data storage devices or installed operating systems. PXE boot is widely used in enterprise environments for network-based installations, diskless workstations, and system recovery.

2. How PXE Boot Works

PXE boot operates through a client-server model:

• a) The client (computer being booted) initiates a network boot sequence.
• b) It broadcasts a DHCP request with PXE-specific options.
• c) A PXE-enabled DHCP server responds with IP configuration and PXE boot server information.
• d) The client downloads a Network Bootstrap Program (NBP) from the PXE server using TFTP.
• e) The NBP is executed, allowing further boot processes or OS installation.

3. PXE Boot Requirements

• Client: Network Interface Card (NIC) with PXE support
• Server: DHCP server with PXE options, TFTP server, and boot images
• Network: Properly configured switches and routers (if applicable)

4. Setting Up a PXE Boot Environment

DHCP Server Configuration:

Configure your DHCP server to provide PXE-specific options:

• Option 66 (Boot Server Host Name): IP address of your TFTP server
• Option 67 (Bootfile Name): Name of the initial boot file (e.g., pxelinux.0)

Example DHCPd configuration:

allow booting;
allow bootp;
option option-128 code 128 = string;
option option-129 code 129 = text;
next-server 192.168.1.10;
filename "pxelinux.0";

TFTP Server Setup:

Install and configure a TFTP server (e.g., tftpd-hpa on Linux):

apt-get install tftpd-hpa

Configure the TFTP root directory (e.g., /var/lib/tftpboot).

Prepare Boot Files:

Download and place necessary boot files in the TFTP root:

• PXELINUX (part of SYSLINUX project)
• Linux kernel and initrd (for Linux installations)
• Windows PE files (for Windows deployments)

Example PXELINUX configuration (pxelinux.cfg/default):

DEFAULT menu.c32
PROMPT 0
MENU TITLE PXE Boot Menu

LABEL linux
    MENU LABEL Install Linux
    KERNEL vmlinuz
    APPEND initrd=initrd.img

LABEL windows
    MENU LABEL Install Windows
    KERNEL memdisk
    INITRD winpe.iso
    APPEND iso raw

5. Advanced PXE Boot Features

iPXE:

iPXE is an open-source network boot firmware that extends PXE capabilities:

• Boot from HTTP, iSCSI, AoE, and more
• Support for wireless networks
• Scripting for complex boot scenarios

Secure Boot:

Implement secure boot with PXE using:

• HTTPS for file transfers
• Digital signatures for boot files
• TPM (Trusted Platform Module) integration

Multicast:

Use multicast for efficient deployment to multiple clients simultaneously:

• Reduce network load during mass deployments
• Requires multicast-enabled network infrastructure

6. Troubleshooting PXE Boot

Common issues and solutions:

• DHCP not providing PXE options: Check DHCP server configuration
• TFTP transfer failures: Verify TFTP server setup and firewall rules
• Boot file not found: Ensure correct file paths and permissions
• NIC compatibility: Update NIC firmware or use iPXE

7. Best Practices

• Regularly update boot images and configurations
• Implement monitoring for PXE services
• Use VLANs to isolate PXE traffic
• Document your PXE environment thoroughly

8. PXE Boot Use Cases

• OS deployment and imaging
• Diskless workstations
• System recovery and diagnostics
• Thin clients and VDI environments

9. Future of PXE Boot

As technology evolves, PXE boot continues to adapt:

• Integration with cloud-based deployment solutions
• Enhanced security features
• Support for newer protocols and hardware

Conclusion:

PXE boot is a powerful tool for network-based system deployment and management. By understanding its components and implementing it correctly, IT professionals can streamline operations and improve system management efficiency in various environments.