pxe-netboot

PXE netboot install (legacy/unreliable remote-media hardware)

When a server's out-of-band virtual-media path (iDRAC/iLO/BMC virtual CD) is broken or unreliable, and USB-boot keeps falling through to whatever OS is already on the internal disks, PXE is the install path that actually works. This is the concrete recipe — a temporary netboot service run from an existing healthy hypervisor on the same network.

When to use this

• The BMC's virtual-media/remote-KVM path is unreliable on this generation of hardware.
• The target's internal disks already carry an OS that keeps re-booting after every USB-boot override the firmware silently drops (a known failure mode on some legacy BMC firmware: a "boot from USB next" flag that should persist behaves as one-shot).
• Any older chassis being added to the fleet later, once you have this recipe built once.

When NOT to use this

• Routine reinstall of an already-healthy node — a verified bootable USB stick is simpler.
• First install on brand-new hardware with guaranteed-blank disks — USB-boot is simpler there too; reach for PXE only once the simple path has actually failed.

Topology

Existing healthy host (same network segment as the target)
  ├── dnsmasq proxyDHCP + TFTP on that interface
  │     → supplements the existing DHCP server with PXE-boot options only,
  │       doesn't replace it
  ├── a plain HTTP server serving kernel + initrd + an answer/config file
  └── a custom-built iPXE binary with an embedded autoexec script

Target chassis
  ├── BMC on its own management network — IPMI-over-LAN reachable
  └── Primary NIC on the same segment as the netboot host — PXE-capable BIOS

Steps (per node)

1. Stage kernel + initrd

Build (or reuse) an auto-install image with a per-node unattended-answer file baked in, then extract just the kernel and initrd from it — you don't need to serve the whole ISO, only the two boot artifacts plus the answer file:

mkdir -p /mnt/iso /srv/http/<target>
mount -o loop /path/to/auto-install.iso /mnt/iso
cp /mnt/iso/boot/<kernel> /mnt/iso/boot/<initrd> /srv/http/<target>/
cp <answer-file> /srv/http/<target>/answer.toml
umount /mnt/iso