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every.channel/evolution/proposals/ECP-0087-lan-capable-ipxe-qemu-module.md

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ECP-0087: LAN-Capable iPXE/QEMU VM Module

Status: Implemented

Context

every.channel already has reusable runner and netboot modules, but hosts that want a continuously-running iPXE test VM still have to carry ad hoc QEMU glue. That makes boot-path verification and downstream reuse harder, and it prevents hosts from declaratively opting into a LAN-visible guest for tuner discovery.

Decision

  1. Add nixosModules.ec-ipxe-qemu at nix/modules/ec-ipxe-qemu.nix.
  2. Add a dedicated publisher guest module/output pair:
    • nixosModules.ec-publisher-guest
    • nixosConfigurations.ec-publisher-x86_64
    • nixosConfigurations.ec-publisher-x86_64-netboot This keeps the VM path explicitly publisher-oriented while leaving host-specific tuner/broadcast choices to downstream configs.
  3. Define services.every-channel.ipxe-qemu.* options for:
    • persistent qcow2/state directory handling,
    • user-mode iPXE boot networking that chains to a configurable internet boot URL,
    • optional second NIC via macvtap for non-disruptive LAN presence,
    • guest sizing and raw QEMU argument overrides.
  4. Run the guest as a persistent systemd service (every-channel-ipxe-qemu) with restart-on-exit semantics so host restarts or config switches naturally refresh the in-memory booted VM.
  5. Enable one conservative instance on ecp-forge using the user-mode boot path only, so the module is exercised in-repo without assuming a local tuner LAN on the forge host.

Alternatives Considered

  • Keep host-specific shell glue outside every.channel. Rejected because downstream hosts cannot reuse or review the boot path as a first-class module.
  • Require a Linux bridge on the host for LAN access. Rejected for now because it is more disruptive than macvtap and unnecessary for an initial deployment.
  • Boot only with QEMU user networking. Rejected because tuner discovery needs a real LAN attachment on some hosts.

Rollout / Teardown

  • Rollout:
    • import nixosModules.ec-ipxe-qemu,
    • enable services.every-channel.ipxe-qemu,
    • set lan.enable = true plus lan.macvtap.interface on hosts that need LAN discovery.
  • Teardown:
    • disable services.every-channel.ipxe-qemu.enable,
    • remove host options,
    • fall back to ad hoc QEMU or direct host publishers if needed.