Rebuild PXE provisioning with iPXE and ProxyDHCP

[greksw]

Summary

Rebuilds the legacy PXE installer into a portfolio-ready Linux provisioning toolkit while preserving repository history.

Main changes

• replaces the old PXELINUX/ThinStation-centric flow with iPXE chainloading;
• keeps the existing site DHCP server authoritative and uses dnsmasq in ProxyDHCP mode;
• supports both legacy BIOS (undionly.kpxe) and x86_64 UEFI (ipxe-snponly-x86_64.efi);
• uses TFTP only for the small iPXE chainloader and HTTP/nginx for boot assets;
• removes hard-coded internal production addresses and uses documentation-safe example values;
• removes embedded SMB credentials and CIFS mount management;
• removes personal GitHub SSH key generation and interactive chroot automation;
• separates PXE service installation from OS-media publishing;
• verifies local ISO images with an operator-supplied SHA-256 before publishing them;
• adds example AlmaLinux and Ubuntu Server boot profiles;
• leaves firewall policy and the primary DHCP server untouched;
• adds a comprehensive README and reference iPXE menu template;
• adds Bash syntax and ShellCheck CI.

Architecture

Existing DHCP provides IP/gateway/DNS. dnsmasq only answers PXE discovery in proxy mode. Firmware receives an iPXE chainloader over TFTP, then iPXE retrieves the menu and installation assets over HTTP.

Follow-up

After review, the repository can be renamed to linux-pxe-provisioning. The separate pxe_server2 repository can then be archived because its useful multi-distribution provisioning concept is represented in this v2 implementation.

Validation status

GitHub Actions Bash syntax validation and ShellCheck pass on the current branch. End-to-end BIOS/UEFI network boot should still be validated on a disposable VM or isolated provisioning VLAN before production use.