# Rebuild plan & decisions log

## Where we started (2026-09-19)

- Old cluster: Docker Swarm (manager planck001) with Portainer, Traefik, and
  what appears to be CapRover remnants. Broken: workers stuck in "pending"
  because the manager's IP changed (workers dial stale `192.168.1.173:2377`).
- Decision: **wipe everything and rebuild clean** rather than repair.

## Hardware

- 20× Raspberry Pi 4 Model B Rev 1.4, 8GB RAM, 4 cores
- Boot: 238.5GB USB SSD on every node (no SD cards installed)
- Bootloader EEPROM: 2023/01/11 on 19 nodes; planck019 has Feb 2021 (update it)
- All nodes healthy: temps 43–52°C, disks ~4% used

## Network

- Ubiquiti UDM Pro, 2 switches, all nodes on the same router
- IPs currently drift across 192.168.0/1/2.x subnets via DHCP — planck001 sits
  on 192.168.30.x (different subnet, cause unknown, doesn't matter: we're
  rebuilding)
- Decision: **dedicated static addressing for the cluster** via UniFi DHCP
  reservations (MAC table in `docs/MACS.txt`)

## Storage

- Synology NAS on same LAN — shared storage target (NFS) for cluster
  workloads

## Rebuild architecture (decided 2026-09-19)

Fully unattended network reimage, no per-node physical access:

- **Synology** (`192.168.1.157`) hosts three services (all auto-start, see
  `configs/`):
  - `planck-tftp.service` — custom python TFTP server on :69 serving
    `/volume1/plancknetboot/tftp/` (firmware, kernel, installer initramfs)
  - `planck-netboot.service` — python HTTP helper on :8000 (GET `rootfs.tar`
    template, GET `/events/<name>` progress log, POST = upload)
  - NFS read-only export of the share for future use
- **Installer initramfs** (`configs/installer-init.sh`): busybox + sfdisk +
  e2fsprogs. Identifies the node by CPU serial (map in
  `configs/hostmap`), wipes `/dev/sda`, downloads the Debian 13 Raspberry Pi
  OS Lite template over HTTP, installs it, sets hostname/ssh keys/user,
  POSTs `pieeprom-revert.upd/.sig` to `tftp/<serial>/`, reboots.
- **Bootloader flow**: nodes' EEPROM is flashed (via staged `pieeprom.upd`
  from the old OS) to install-mode: `BOOT_ORDER=0xf142` (network first),
  `TFTP_IP=192.168.1.157`, `TFTP_PREFIX=1` (per-serial dirs),
  `ENABLE_SELF_UPDATE=1`. After install, the TFTP-served
  `bootloader_update=1` config + `<serial>/pieeprom.upd` reverts the node to
  `BOOT_ORDER=0xf14` (USB first). Fresh OS boots from SSD; firstboot service
  tidies up.
- **Reinstall a node anytime**: stage install-mode EEPROM again + reboot
  (delete `tftp/<serial>/pieeprom.*` on the Synology first if it exists).
- Node password: see `configs/node-password.txt` (gitignored). SSH is
  key-based; password exists for console/sudo recovery.
- UniFi MFA blocks API access; DHCP reservations deferred — mDNS
  (`planck0NN.local`) works across subnets today.

## Phases

- [x] Phase 0 — Access + inventory (SSH keys on all 20, docs/)
- [ ] Phase 1 — Network design: static IPs / reservations in UniFi
- [ ] Phase 2 — Reimage all 20 nodes with fresh Raspberry Pi OS
- [ ] Phase 3 — Cluster runtime install (candidates: k3s vs Docker Swarm)
- [ ] Phase 4 — Storage integration with Synology (NFS CSI)
- [ ] Phase 5 — Apps: monitoring, Portainer/UI, whatever the lab is for

## Open decisions

1. **Reimage method** — options:
   a. PXE/network boot: EEPROM boot-order set to netboot; DHCP next-server
      points at a TFTP/HTTP installer. Zero-touch per node, reusable forever.
      Installer server can run on the Synology (Docker) or a laptop.
   b. SD-card bootstrap installer: flash one SD image, insert per node, it
      wipes + installs the USB SSD, removes itself. Simple, physical walk.
   c. Pull SSDs, image on a PC with Raspberry Pi Imager ×20. Most manual.
2. **Cluster runtime** — k3s (lighter, k8s-compatible, we manage it with
   automation) vs Docker Swarm + Portainer (simplest).