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fix(B-0792 iter-5.2.2): hostname auto-gen at install-time NOT flash-time (multi-node reuse fix) + login-banner shows hostname pre-login (Aaron 2026-05-26) #5113

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Merged
AceHack merged 1 commit into from
May 26, 2026
Merged

fix(B-0792 iter-5.2.2): hostname auto-gen at install-time NOT flash-time (multi-node reuse fix) + login-banner shows hostname pre-login (Aaron 2026-05-26) #5113

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8 changes: 7 additions & 1 deletion full-ai-cluster/nixos/modules/common.nix
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Expand Up @@ -8,7 +8,13 @@
# iter-5.2 (B-0792): per-node hostname injection lives in its own
# module so every host (control-plane, worker-gpu, worker-template,
# future configs) inherits the override capability automatically.
imports = [ ./injected-hostname.nix ];
# iter-5.2.2 adds login-banner.nix — shows hostname + ssh hint at
# console pre-login per the maintainer 2026-05-26 photo-friendly
# diagnostic discipline.
imports = [
./injected-hostname.nix
./login-banner.nix
];

nix.settings = {
experimental-features = [ "nix-command" "flakes" ];
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62 changes: 62 additions & 0 deletions full-ai-cluster/nixos/modules/login-banner.nix
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@@ -0,0 +1,62 @@
# full-ai-cluster/nixos/modules/login-banner.nix
#
# iter-5.2.2 (B-0792): NixOS getty login-banner customization so the
# hostname (+ primary IP + ssh-from-Mac hint) is visible BEFORE the
# operator logs in at the console.
Comment on lines +4 to +5
#
# Problem the maintainer 2026-05-26 surfaced: *"i mean i see a login
# but no hostname until after i login can you update to show hostname
# before i login"* — NixOS default getty shows just "login:" without
# the hostname when the hostname is generic/default. Even when
# `networking.hostName` is set, the getty issue file doesn't
# necessarily display it prominently.
#
# Fix: configure `services.getty.greetingLine` + `services.getty.helpLine`
# so the pre-login console shows:
#
# ╭────────────────────────────────────────────────────╮
# │ ZETA CLUSTER NODE │
# │ Hostname: <hostname> │
# │ SSH from operator Mac: │
# │ ssh zeta@<hostname>.local │
# │ Console login: │
# │ user: zeta │
# │ password: zeta-change-me (rotate after first) │
# ╰────────────────────────────────────────────────────╯
# <hostname> login:
#
# Photo-friendly per the maintainer's 2026-05-26 *"whenever i have
# to ferry commands by reading and typing i'm going to avoid it
# like the plague and try to get like pictures and auto run and
# short commands pre built in"* discipline.

{ config, lib, ... }:

let
hostName = config.networking.hostName;
in
{
# services.getty.greetingLine: printed once before login prompt.
# services.getty.helpLine: printed after greeting; conventionally
# the multi-line block goes here so each VT shows the same banner.
# \\n in literal NixOS string becomes "\n" in /etc/issue, which
# agetty expands to the system hostname at runtime.
Comment on lines +42 to +43
services.getty.greetingLine = "<<< Welcome to ${hostName} (Zeta cluster node) >>>";
services.getty.helpLine = ''


╭─────────────────────────────────────────────────────────╮
│ ZETA CLUSTER NODE │
│ │
│ Hostname: ${hostName} │
│ │
│ SSH from operator Mac (zero-typing if pubkey injected):│
│ ssh zeta@${hostName}.local │
│ │
│ Console login (if needed for diagnostics): │
│ user: zeta │
│ password: zeta-change-me (rotate after first login) │
╰─────────────────────────────────────────────────────────╯

'';
}
54 changes: 29 additions & 25 deletions full-ai-cluster/tools/zflash.ts
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Expand Up @@ -910,35 +910,39 @@ async function main() {
willInject = false;
}

// iter-5.2.1 (B-0792): if operator didn't pass --host, auto-generate
// a random unique hostname `node-<6hex>` (24-bit entropy = ~16M
// possible names, negligible collision risk for any homelab cluster
// size; node-by-node mDNS uniqueness preserved). Operator can rename
// later via the digital-twin substrate planned under B-0794 (node
// self-registration; not yet shipped — see B-0794 row for the
// target node-config substrate that will host the rename mechanism).
// iter-5.2.2 (B-0792) — REVERTS iter-5.2.1 flash-time auto-generation:
//
// The maintainer 2026-05-26: "can we have it auto generate the host
// name we can change later via digital twin after it self registers."
// The maintainer 2026-05-26 surfaced the design flaw with flash-time
// auto-generation: *"wait zflash has a hard coded name? i was
// thinking it would be auto generated on each machine so i can't
// use that same usb twice?"* — baking a name into the ESP at flash
// time meant every install from the same USB inherits the SAME
// hostname, causing mDNS collision when reused across machines.
//
// Auto-gen happens only when --host was NOT passed (preserves
// operator intent when they did pick a name) AND when iter-4.2
// inject will actually run (gated on `willInject` so we never
// promise an ssh target for a hostname that won't be written to
// the USB ESP — finalized AFTER the pubkey existence check so
// missing-pubkey path doesn't print a misleading ssh promise).
// Fix: when --host is NOT passed, DON'T write zeta-hostname.txt
// to the ESP. zeta-install.sh now generates a fresh random
// node-<6hex> ON THE NODE at install time (per-install unique).
// Each install from the same USB gets a different hostname.
//
// Operator paths:
// - `zflash --host pikachu` → ESP carries 'pikachu'; install honors
// - `zflash` (no --host) → ESP has no hostname; install auto-gens
// on-node + prints in install banner +
// displays in pre-login banner per
// iter-5.2.2 NixOS login-banner module.
//
// The previous iter-5.2.1 "log the auto-name pre-flash so operator
// knows what to ssh to" UX is lost in trade — operator now reads
// the auto-name from the cluster console's login banner (printed
// pre-login per iter-5.2.2 login-banner module) OR from mDNS scan.
// Right trade for multi-node correctness.
if (hostOverride === null && willInject) {
// Web Crypto: 3 random bytes → 6 hex chars; node-XXXXXX. Prefix
// `node-` keeps the namespace clean (operator-named hosts can
// avoid the `node-` prefix to distinguish from auto-named).
const rand = new Uint8Array(3);
crypto.getRandomValues(rand);
const hex = Array.from(rand, (b) => b.toString(16).padStart(2, "0")).join("");
hostOverride = `node-${hex}`;
process.stdout.write(
`\niter-5.2.1: --host not specified; auto-generated hostname: ${hostOverride}\n` +
` (rename later via B-0794 digital-twin substrate when shipped)\n` +
` cluster will be reachable as: ssh zeta@${hostOverride}.local\n\n`,
`\niter-5.2.2: --host not specified; zeta-install.sh on-node will\n` +
` auto-generate a unique node-<6hex> hostname per-install.\n` +
` Pre-login banner on first boot displays the chosen hostname\n` +
` + IP (per iter-5.2.2 NixOS login-banner module).\n` +
` For memorable names, re-flash with: zflash --host <name>\n\n`,
);
}

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30 changes: 29 additions & 1 deletion full-ai-cluster/usb-nixos-installer/zeta-install.sh
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Expand Up @@ -402,8 +402,36 @@ if [ -n "$HOSTNAME_FILE" ]; then
echo "[iter-5.2] falling back to flake default ($HOST)"
fi
else
# iter-5.2.2 fix (B-0792): when no operator-explicit hostname is
# on the ESP, generate a fresh random hostname ON THE NODE at
# install time (NOT at flash time). This is the load-bearing fix
# for the "same USB reused on second machine" multi-node case
# the maintainer 2026-05-26 surfaced: *"i was thinking it would
# be auto generated on each machine so i can't use that same
# usb twice?"*. zflash no longer auto-generates at flash time;
# zeta-install.sh now generates per-install. Each install from
# the same USB gets a unique node-<6hex> hostname.
#
# Format: node-<6hex> from /dev/urandom (24-bit entropy =
# ~16M unique names; negligible collision risk for any homelab
# cluster size; mDNS uniqueness preserved per-node).
echo "[iter-5.2] no zeta-hostname.txt on USB ESP"
echo "[iter-5.2] using flake default hostname for #$HOST"
echo "[iter-5.2.2] generating fresh random hostname on-node (per-install unique) ..."
GENERATED_HOSTNAME="node-$(head -c 3 /dev/urandom | xxd -p)"
if echo "$GENERATED_HOSTNAME" \
| grep -Eq '^[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?$'; then
echo "[iter-5.2.2] generated: $GENERATED_HOSTNAME"
sudo mkdir -p "$(dirname "$HOSTNAME_DST")"
echo "$GENERATED_HOSTNAME" | sudo tee "$HOSTNAME_DST" >/dev/null
sudo chmod 0644 "$HOSTNAME_DST"
echo "[iter-5.2.2] wrote $HOSTNAME_DST"
echo "[iter-5.2.2] networking.hostName will be '$GENERATED_HOSTNAME' on first boot"
echo "[iter-5.2.2] ssh access: ssh zeta@${GENERATED_HOSTNAME}.local"
echo "[iter-5.2.2] *** REMEMBER THIS HOSTNAME *** — printed in login banner per iter-5.2.2 substrate"
else
echo "[iter-5.2.2] WARN: generation produced invalid hostname '$GENERATED_HOSTNAME'"
echo "[iter-5.2.2] falling back to flake default ($HOST)"
fi
fi
echo

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