refactor(gc-hosts): discover running pve1 guests dynamically each run

Replace the static host list with dynamic discovery: workstation (nixos)
and pve1 are hard-wired first and second; remaining hosts are discovered
on every run by SSHing to pve1, listing running VMs/containers via
pct/qm list, and resolving their NixOS hostnames from a single flake eval.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/gc-hosts.sh

@@ -1,159 +1,179 @@
 #!/usr/bin/env bash
-# gc-hosts.sh — Run nix-collect-garbage -d on all live NixOS hosts and pve1.
+# gc-hosts.sh — Run nix-collect-garbage -d on all live NixOS hosts.
 #
-# nix-cache is excluded: it is the shared binary cache for all other hosts, so
+# The host list is rebuilt on every run:
-# gc-ing it would evict cached store paths and force costly rebuilds elsewhere.
+#   1. This workstation (nixos) — always first
+#   2. pve1 — always second (non-NixOS Proxmox node with Nix installed)
+#   3. Every NixOS guest currently running on pve1 (discovered via pct/qm list)
 #
-# Runs SSH jobs in parallel (up to MAX_JOBS at a time) and prints a summary.
+# nix-cache is excluded: gc-ing the shared binary cache evicts store paths
+# that other hosts depend on for substitution.
+#
+# NixOS hosts: tries "sudo -n nix-collect-garbage -d" first (works when
+# wheelNeedsPassword = false, e.g. the HA cluster).  Falls back to user-level
+# "nix-collect-garbage -d" if sudo needs a password — still collects
+# unreferenced store paths and old nixos-user profile generations, but leaves
+# old system generations in place.
+# pve1: runs "nix-collect-garbage -d" as the login user (no system generations
+# on a non-NixOS host).
 #
 # Usage (from repo root):
-#   bash scripts/gc-hosts.sh [--dry-run] [<hostname> ...]
+#   bash scripts/gc-hosts.sh [--dry-run]
-#
-# Options:
-#   --dry-run     Print the SSH commands without executing them.
-#   <hostname>    Limit to the given hostnames (bare names, no domain suffix).
-#                 Default: all hosts in the list below.
-#
-# Sudo notes:
-#   NixOS hosts: tries "sudo -n nix-collect-garbage -d" first (non-interactive,
-#   works when wheelNeedsPassword = false such as on the HA cluster).  Falls
-#   back to "nix-collect-garbage -d" as the nixos user if sudo requires a
-#   password — this still collects unreferenced store paths and removes old
-#   nixos-user profile generations, but will not remove old system generations.
-#   pve1: non-NixOS Proxmox node, runs nix-collect-garbage -d as wayne (no
-#   system generations to delete).
 
 set -euo pipefail
 cd "$(dirname "$0")/.."
 source scripts/env.sh 2>/dev/null || true
+source scripts/lib/nix-eval.sh 2>/dev/null || true
 
 # ── config ────────────────────────────────────────────────────────────────────
 
-: "${MAX_JOBS:=6}"
+: "${MAX_JOBS:=8}"
 : "${NIXOS_USER:=nixos}"
+: "${PVE1_SSH_USER:=${PROXMOX_SSH_USER:-wayne}}"
 SSH_OPTS=(-o StrictHostKeyChecking=no -o BatchMode=yes -o ConnectTimeout=10)
 
-# Map: hostname → ssh-user
-# Update this list when new hosts are added/removed.
-declare -A HOSTS=(
-  [docker]="$NIXOS_USER"
-  [ha-server-1]="$NIXOS_USER"
-  [ha-server-2]="$NIXOS_USER"
-  [nix-minimal]="$NIXOS_USER"
-  [nixos]="$NIXOS_USER"
-  [pxe-boot]="$NIXOS_USER"
-  [server]="$NIXOS_USER"
-  [tailscale-router]="$NIXOS_USER"
-  [tor-relay]="$NIXOS_USER"
-  [pve1]="${PROXMOX_SSH_USER:-wayne}"
-)
-
-# ── argument parsing ──────────────────────────────────────────────────────────
-
 DRY_RUN=0
-FILTER=()
-
 for arg in "$@"; do
   case "$arg" in
     --dry-run) DRY_RUN=1 ;;
-    --*)       echo "Unknown option: $arg" >&2; exit 1 ;;
+    *) echo "Unknown option: $arg" >&2; exit 1 ;;
-    *)         FILTER+=("$arg") ;;
   esac
 done
 
-# Resolve the set of (hostname, user) pairs to process.
+# ── build the host list ───────────────────────────────────────────────────────
-declare -A TARGET_USERS
+
-if [[ ${#FILTER[@]} -gt 0 ]]; then
+# ORDERED_HOSTS: names in display/execution order.
-  for h in "${FILTER[@]}"; do
+# HOST_TARGET[name]: SSH target string (user@host).
-    if [[ -z "${HOSTS[$h]+_}" ]]; then
+# HOST_TYPE[name]: "nixos" (try sudo gc, fallback user) | "nix" (user gc only).
-      echo "Unknown hostname: $h (not in the gc-hosts list)" >&2
+declare -a  ORDERED_HOSTS=()
-      exit 1
+declare -A  HOST_TARGET=()
-    fi
+declare -A  HOST_TYPE=()
-    TARGET_USERS[$h]="${HOSTS[$h]}"
+declare -A  _SEEN_HOSTNAMES=()   # dedup tracker
-  done
+
-else
+_add_host() {
-  for h in "${!HOSTS[@]}"; do
+  local name="$1" target="$2" type="$3"
-    TARGET_USERS[$h]="${HOSTS[$h]}"
+  if [[ -n "${_SEEN_HOSTNAMES[$name]+_}" ]]; then return; fi
-  done
+  _SEEN_HOSTNAMES[$name]=1
+  ORDERED_HOSTS+=("$name")
+  HOST_TARGET[$name]="$target"
+  HOST_TYPE[$name]="$type"
+}
+
+# 1. Workstation (hard-wired first)
+_add_host "nixos" "${NIXOS_USER}@nixos" "nixos"
+
+# 2. pve1 (hard-wired second; non-NixOS, no system generations)
+_add_host "pve1" "${PVE1_SSH_USER}@${PVE1_HOST}" "nix"
+
+# 3. Dynamically discover running NixOS guests on pve1
+echo "Discovering running guests on ${PVE1_HOST}..."
+
+# Evaluate the full flake hostname map in one shot.
+hostname_map="{}"
+if ! hostname_map="$(
+  nix eval --json "${NIX_EVAL_FLAGS[@]}" .#nixosConfigurations \
+    --apply 'cfgs: builtins.mapAttrs (_: cfg: cfg.config.networking.hostName) cfgs' \
+    2>/dev/null
+)"; then
+  echo "  warning: flake eval failed — skipping dynamic host discovery" >&2
 fi
 
-SORTED_HOSTS=($(printf '%s\n' "${!TARGET_USERS[@]}" | sort))
+# Get names of all currently running guests from pve1.
+if ssh "${SSH_OPTS[@]}" "${PVE1_SSH_USER}@${PVE1_HOST}" "true" 2>/dev/null; then
+  running_guests="$(
+    ssh "${SSH_OPTS[@]}" "${PVE1_SSH_USER}@${PVE1_HOST}" bash <<'REMOTE'
+      { sudo pct list 2>/dev/null | awk 'NR>1 && $2=="running" { print $NF }';
+        sudo qm  list 2>/dev/null | awk 'NR>1 && $3=="running" { print $2  }'; } | sort -u
+REMOTE
+  )" || running_guests=""
 
-# ── helpers ───────────────────────────────────────────────────────────────────
+  while IFS= read -r guest; do
+    [[ -z "$guest" ]] && continue
+
+    # Resolve flake target name → NixOS hostname.
+    hostname="$(printf '%s' "$hostname_map" \
+      | jq -r --arg g "$guest" '.[$g] // empty' 2>/dev/null || true)"
+    [[ -z "$hostname" ]] && continue
+
+    # Exclude nix-cache and any target whose hostname is already in our list.
+    case "$hostname" in nix-cache) continue ;; esac
+    if [[ -n "${_SEEN_HOSTNAMES[$hostname]+_}" ]]; then continue; fi
+
+    echo "  + $guest → $hostname"
+    _add_host "$hostname" "${NIXOS_USER}@${hostname}" "nixos"
+  done <<< "$running_guests"
+else
+  echo "  warning: ${PVE1_HOST} unreachable — skipping dynamic host discovery" >&2
+fi
+
+echo ""
+echo "Hosts: ${ORDERED_HOSTS[*]}"
+echo ""
+
+# ── dry-run ───────────────────────────────────────────────────────────────────
+
+if [[ "$DRY_RUN" -eq 1 ]]; then
+  echo "[dry-run] commands that would run:"
+  for host in "${ORDERED_HOSTS[@]}"; do
+    target="${HOST_TARGET[$host]}"
+    type="${HOST_TYPE[$host]}"
+    if [[ "$type" == "nixos" ]]; then
+      echo "  ssh ${SSH_OPTS[*]} $target 'sudo -n nix-collect-garbage -d'"
+      echo "  # fallback: ssh ... $target 'nix-collect-garbage -d'"
+    else
+      echo "  ssh ${SSH_OPTS[*]} $target 'nix-collect-garbage -d'"
+    fi
+  done
+  exit 0
+fi
+
+# ── gc worker ─────────────────────────────────────────────────────────────────
 
 gc_one() {
-  local host="$1" user="$2" logfile="$3"
+  local host="$1" target="${HOST_TARGET[$1]}" type="${HOST_TYPE[$1]}" logfile="$2"
-  local target="${user}@${host}"
 
   if ! ssh "${SSH_OPTS[@]}" "$target" "true" 2>>"$logfile"; then
-    echo "unreachable"
+    echo "unreachable"; return
-    return
   fi
 
-  # NixOS hosts: try passwordless sudo first.
+  if [[ "$type" == "nixos" ]]; then
-  if [[ "$user" == "$NIXOS_USER" ]]; then
     if ssh "${SSH_OPTS[@]}" "$target" "sudo -n nix-collect-garbage -d" \
         >>"$logfile" 2>>"$logfile"; then
-      echo "ok(sudo)"
+      echo "ok(sudo)"; return
-      return
     fi
-    # sudo required a password — fall back to user-level gc.
+    echo "[sudo needs password — falling back to user-level gc]" >>"$logfile"
-    echo "[sudo needs password, falling back to user-level gc]" >>"$logfile"
     if ssh "${SSH_OPTS[@]}" "$target" "nix-collect-garbage -d" \
         >>"$logfile" 2>>"$logfile"; then
-      echo "ok(user)"
+      echo "ok(user)"; return
-      return
     fi
   else
-    # Non-NixOS node (pve1): no system generations; just gc as the login user.
     if ssh "${SSH_OPTS[@]}" "$target" "nix-collect-garbage -d" \
         >>"$logfile" 2>>"$logfile"; then
-      echo "ok"
+      echo "ok"; return
-      return
     fi
   fi
 
   echo "failed:$?"
 }
 
-# ── dry-run ───────────────────────────────────────────────────────────────────
-
-if [[ "$DRY_RUN" -eq 1 ]]; then
-  echo "[dry-run] would run gc on: ${SORTED_HOSTS[*]}"
-  for host in "${SORTED_HOSTS[@]}"; do
-    user="${TARGET_USERS[$host]}"
-    if [[ "$user" == "$NIXOS_USER" ]]; then
-      echo "  ssh ${SSH_OPTS[*]} ${user}@${host} 'sudo -n nix-collect-garbage -d'"
-      echo "  # fallback: ssh ... 'nix-collect-garbage -d'"
-    else
-      echo "  ssh ${SSH_OPTS[*]} ${user}@${host} 'nix-collect-garbage -d'"
-    fi
-  done
-  exit 0
-fi
-
 # ── parallel execution ────────────────────────────────────────────────────────
 
+echo "Running gc on ${#ORDERED_HOSTS[@]} hosts (up to ${MAX_JOBS} parallel)..."
+echo ""
+
 TMPDIR_GC="$(mktemp -d)"
 trap 'rm -rf "$TMPDIR_GC"' EXIT
 
-declare -A LOGS
+declare -A LOGS=()
-
-echo "Running gc on ${#SORTED_HOSTS[@]} hosts (up to ${MAX_JOBS} parallel)..."
-echo ""
-
 job_count=0
-for host in "${SORTED_HOSTS[@]}"; do
+
-  user="${TARGET_USERS[$host]}"
+for host in "${ORDERED_HOSTS[@]}"; do
   logfile="${TMPDIR_GC}/${host}.log"
   resultfile="${TMPDIR_GC}/${host}.result"
   LOGS[$host]="$logfile"
   : > "$logfile"
 
-  (
+  ( result="$(gc_one "$host" "$logfile")"; echo "$result" > "$resultfile" ) &
-    result="$(gc_one "$host" "$user" "$logfile")"
-    echo "$result" > "$resultfile"
-  ) &
 
   (( job_count++ )) || true
   if [[ "$job_count" -ge "$MAX_JOBS" ]]; then
@@ -173,30 +193,24 @@ ok_hosts=()
 warn_hosts=()
 fail_hosts=()
 
-for host in "${SORTED_HOSTS[@]}"; do
+for host in "${ORDERED_HOSTS[@]}"; do
-  resultfile="${TMPDIR_GC}/${host}.result"
+  result="$(cat "${TMPDIR_GC}/${host}.result" 2>/dev/null || echo "failed:missing")"
-  result="$(cat "$resultfile" 2>/dev/null || echo "failed:missing")"
-
   case "$result" in
     ok|"ok(sudo)"|"ok(user)")
-      printf "  %-20s  %s\n" "$host" "$result"
+      printf "  %-22s  %s\n" "$host" "$result"
-      ok_hosts+=("$host")
+      ok_hosts+=("$host") ;;
-      ;;
     unreachable)
-      printf "  %-20s  UNREACHABLE\n" "$host"
+      printf "  %-22s  UNREACHABLE\n" "$host"
-      warn_hosts+=("$host")
+      warn_hosts+=("$host") ;;
-      ;;
     *)
-      printf "  %-20s  FAILED (%s)\n" "$host" "$result"
+      printf "  %-22s  FAILED (%s)\n" "$host" "$result"
-      fail_hosts+=("$host")
+      fail_hosts+=("$host") ;;
-      ;;
   esac
 done
 
 echo ""
 echo "  ${#ok_hosts[@]} succeeded, ${#warn_hosts[@]} unreachable, ${#fail_hosts[@]} failed"
 
-# Print logs for any non-ok host.
 for host in "${warn_hosts[@]+"${warn_hosts[@]}"}" "${fail_hosts[@]+"${fail_hosts[@]}"}"; do
   logfile="${LOGS[$host]}"
   if [[ -s "$logfile" ]]; then