Deduplicate reusable shell code in scripts/ into scripts/lib/

Three chunks of copy-pasted logic were drifting across scripts/*.sh:
- codex-setup.sh and codex-maintenance.sh each carried an identical
  NIX_CONFIG bootstrap + ensure_nix_profile() -> scripts/lib/nix-bootstrap.sh
- sync-host-keys.sh and prepare-host-key.sh each ran the same
  ssh-keygen/ssh-to-age nix-shell invocations -> scripts/lib/ssh-host-keys.sh
  (prepare-host-key.sh now also calls env.sh's nix_extra_opts before using
  them, closing a gap where it alone skipped the nix-cache reachability
  check env.sh exists for)
- the "list nixosConfigurations attrNames" / "get one target's hostName"
  nix eval pattern was repeated across codex-setup.sh, codex-maintenance.sh,
  sync-host-keys.sh and create-proxmox-resource.sh (the latter twice, in
  its own --list and --host lookup) -> scripts/lib/nix-eval.sh, which also
  centralizes the --no-use-registries --no-accept-flake-config flag pair
  used on every such call

Verified against the real flake/node config (nix is available here):
create-proxmox-resource.sh --list for both --type lxc/vm, a full
--dry-run create, and prepare-host-key.sh generating and cleaning up a
real key/age-pubkey pair.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/codex-maintenance.sh

@@ -1,22 +1,14 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-export NIX_CONFIG="${NIX_CONFIG:-}
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-experimental-features = nix-command flakes
+# shellcheck source=lib/nix-bootstrap.sh
-accept-flake-config = false
+source "${script_dir}/lib/nix-bootstrap.sh"
-warn-dirty = false
+# shellcheck source=lib/nix-eval.sh
-"
+source "${script_dir}/lib/nix-eval.sh"
 
 MODE="${1:-validate}"
 
-ensure_nix_profile() {
-  if [ -f /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh ]; then
-    . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
-  elif [ -f "$HOME/.nix-profile/etc/profile.d/nix.sh" ]; then
-    . "$HOME/.nix-profile/etc/profile.d/nix.sh"
-  fi
-}
-
 ensure_nix_profile
 
 if ! command -v nix >/dev/null 2>&1; then
@@ -24,8 +16,7 @@ if ! command -v nix >/dev/null 2>&1; then
   exit 127
 fi
 
-hosts_json="$(nix eval --json --no-use-registries --no-accept-flake-config .#nixosConfigurations --apply builtins.attrNames)"
+hosts="$(list_flake_targets .)"
-hosts="$(echo "$hosts_json" | jq -r '.[]')"
 
 echo "Hosts:"
 echo "$hosts"
@@ -44,17 +35,17 @@ fi
 
 echo
 echo "Checking Nix formatting with nixpkgs-fmt..."
-nix run --no-use-registries --no-accept-flake-config github:NixOS/nixpkgs/nixos-25.11#nixpkgs-fmt -- --check .
+nix run "${NIX_EVAL_FLAGS[@]}" github:NixOS/nixpkgs/nixos-25.11#nixpkgs-fmt -- --check .
 
 echo
 echo "Running statix lint..."
-nix run --no-use-registries --no-accept-flake-config github:NixOS/nixpkgs/nixos-25.11#statix -- check .
+nix run "${NIX_EVAL_FLAGS[@]}" github:NixOS/nixpkgs/nixos-25.11#statix -- check .
 
 echo
 echo "Evaluating host toplevel derivations..."
 for host in $hosts; do
   echo "==> $host"
-  nix eval --raw --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.toplevel.drvPath"
+  nix eval --raw "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.toplevel.drvPath"
 
   # lxc-* hosts deploy via a directly pct-restore-able tarball instead of
   # nixos-install (see docs/auto-installer.md); proxmox-* hosts can
@@ -64,22 +55,21 @@ for host in $hosts; do
   case "$host" in
     lxc-*)
       echo "==> $host (tarball)"
-      nix eval --raw --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.tarball.drvPath"
+      nix eval --raw "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.tarball.drvPath"
       ;;
     proxmox-*)
       echo "==> $host (diskoImagesScript)"
-      nix eval --raw --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.diskoImagesScript.drvPath"
+      nix eval --raw "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.diskoImagesScript.drvPath"
       ;;
   esac
 done
 
 echo
 echo "Evaluating buildable packages..."
-packages_json="$(nix eval --json --no-use-registries --no-accept-flake-config .#packages.x86_64-linux --apply builtins.attrNames)"
+packages="$(nix eval --json "${NIX_EVAL_FLAGS[@]}" .#packages.x86_64-linux --apply builtins.attrNames | jq -r '.[]')"
-packages="$(echo "$packages_json" | jq -r '.[]')"
 for pkg in $packages; do
   echo "==> packages.x86_64-linux.${pkg}"
-  nix eval --raw --no-use-registries --no-accept-flake-config ".#packages.x86_64-linux.${pkg}"
+  nix eval --raw "${NIX_EVAL_FLAGS[@]}" ".#packages.x86_64-linux.${pkg}"
 done
 
 if [[ "$MODE" == "dry-run" ]]; then
@@ -87,16 +77,16 @@ if [[ "$MODE" == "dry-run" ]]; then
   echo "Running dry-run builds for all hosts. This will not create result symlinks."
   for host in $hosts; do
     echo "==> Dry-run build: $host"
-    nix build --dry-run --no-link --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.toplevel"
+    nix build --dry-run --no-link "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.toplevel"
 
     case "$host" in
       lxc-*)
         echo "==> Dry-run build: $host (tarball)"
-        nix build --dry-run --no-link --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.tarball"
+        nix build --dry-run --no-link "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.tarball"
         ;;
       proxmox-*)
         echo "==> Dry-run build: $host (diskoImagesScript)"
-        nix build --dry-run --no-link --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.diskoImagesScript"
+        nix build --dry-run --no-link "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.diskoImagesScript"
         ;;
     esac
   done
@@ -105,7 +95,7 @@ if [[ "$MODE" == "dry-run" ]]; then
   echo "Running dry-run builds for all packages."
   for pkg in $packages; do
     echo "==> Dry-run build: packages.x86_64-linux.${pkg}"
-    nix build --dry-run --no-link --no-use-registries --no-accept-flake-config ".#packages.x86_64-linux.${pkg}"
+    nix build --dry-run --no-link "${NIX_EVAL_FLAGS[@]}" ".#packages.x86_64-linux.${pkg}"
   done
 fi
 

scripts/codex-setup.sh

@@ -1,19 +1,11 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-export NIX_CONFIG="${NIX_CONFIG:-}
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-experimental-features = nix-command flakes
+# shellcheck source=lib/nix-bootstrap.sh
-accept-flake-config = false
+source "${script_dir}/lib/nix-bootstrap.sh"
-warn-dirty = false
+# shellcheck source=lib/nix-eval.sh
-"
+source "${script_dir}/lib/nix-eval.sh"
-
-ensure_nix_profile() {
-  if [ -f /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh ]; then
-    . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
-  elif [ -f "$HOME/.nix-profile/etc/profile.d/nix.sh" ]; then
-    . "$HOME/.nix-profile/etc/profile.d/nix.sh"
-  fi
-}
 
 install_nix_if_missing() {
   if command -v nix >/dev/null 2>&1; then
@@ -79,13 +71,13 @@ if ! command -v jq >/dev/null 2>&1; then
 fi
 
 echo "Available NixOS hosts:"
-hosts="$(nix eval --json --no-use-registries --no-accept-flake-config .#nixosConfigurations --apply builtins.attrNames | jq -r '.[]')"
+hosts="$(list_flake_targets .)"
 echo "$hosts"
 
 echo "Evaluating all host toplevel derivations..."
 for host in $hosts; do
   echo "==> Evaluating $host"
-  nix eval --raw --no-use-registries --no-accept-flake-config ".#nixosConfigurations.${host}.config.system.build.toplevel.drvPath"
+  nix eval --raw "${NIX_EVAL_FLAGS[@]}" ".#nixosConfigurations.${host}.config.system.build.toplevel.drvPath"
 done
 
 echo "Codex setup complete."

scripts/create-proxmox-resource.sh

@@ -26,6 +26,8 @@ set -euo pipefail
 repo_root="$(cd "$(dirname "$0")/.." && pwd)"
 # shellcheck source=env.sh
 source "${repo_root}/scripts/env.sh"
+# shellcheck source=lib/nix-eval.sh
+source "${repo_root}/scripts/lib/nix-eval.sh"
 
 sync_keys="${repo_root}/scripts/sync-host-keys.sh"
 
@@ -240,15 +242,21 @@ platform_prefix="lxc"
 [[ -z "$memory" ]] && memory="$PROXMOX_DEFAULT_MEMORY_MB"
 
 # --- discover / resolve the flake target from --host --------------------
+# Emits "<target>\t<hostName>" pairs for every ${platform_prefix}-* flake
+# target -- the one source both --list and the --host lookup below read
+# from, so they can never see a different set of targets from each other.
+targets_for_platform() {
+  local target
+  for target in $(list_flake_targets "$repo_root" 2>/dev/null | grep -- "^${platform_prefix}-"); do
+    printf '%s\t%s\n' "$target" "$(flake_target_hostname "$repo_root" "$target")"
+  done
+}
+
 list_hosts() {
   local target hostname
-  for target in $(nix eval --json --no-use-registries --no-accept-flake-config \
+  while IFS=$'\t' read -r target hostname; do
-    "${repo_root}#nixosConfigurations" --apply builtins.attrNames 2>/dev/null \
-    | jq -r --arg p "${platform_prefix}-" '.[] | select(startswith($p))'); do
-    hostname="$(nix eval --raw --no-use-registries --no-accept-flake-config \
-      "${repo_root}#nixosConfigurations.${target}.config.networking.hostName" 2>/dev/null)"
     printf '  %-12s -> %s\n' "$hostname" "$target"
-  done
+  done < <(targets_for_platform)
 }
 
 if [[ "$do_list" -eq 1 ]]; then
@@ -263,16 +271,12 @@ if [[ -z "$host" ]]; then
 fi
 
 flake_target=""
-for target in $(nix eval --json --no-use-registries --no-accept-flake-config \
+while IFS=$'\t' read -r target hostname; do
-  "${repo_root}#nixosConfigurations" --apply builtins.attrNames \
+  if [[ "$hostname" == "$host" ]]; then
-  | jq -r --arg p "${platform_prefix}-" '.[] | select(startswith($p))'); do
-  hn="$(nix eval --raw --no-use-registries --no-accept-flake-config \
-    "${repo_root}#nixosConfigurations.${target}.config.networking.hostName")"
-  if [[ "$hn" == "$host" ]]; then
     flake_target="$target"
     break
   fi
-done
+done < <(targets_for_platform)
 
 if [[ -z "$flake_target" ]]; then
   echo "ERROR: no ${platform_prefix}-* target has hostName '${host}'." >&2

scripts/lib/nix-bootstrap.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+# Shared Nix bootstrap for scripts/codex-setup.sh and
+# scripts/codex-maintenance.sh: the nix.conf settings both need in effect
+# before a single `nix` command runs (flakes enabled, never honor a flake
+# input's own nixConfig, no "dirty tree" warning spam), plus a helper to
+# pull an already-installed Nix's daemon/profile script onto PATH if it
+# isn't there yet. Source this instead of copying it -- see CLAUDE.md.
+export NIX_CONFIG="${NIX_CONFIG:-}
+experimental-features = nix-command flakes
+accept-flake-config = false
+warn-dirty = false
+"
+
+ensure_nix_profile() {
+  if [ -f /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh ]; then
+    . /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
+  elif [ -f "$HOME/.nix-profile/etc/profile.d/nix.sh" ]; then
+    . "$HOME/.nix-profile/etc/profile.d/nix.sh"
+  fi
+}

scripts/lib/nix-eval.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# Shared flake-introspection helpers for scripts/*.sh. Source alongside
+# env.sh:
+#   source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/lib/nix-eval.sh"
+#
+# NIX_EVAL_FLAGS: --no-use-registries so a call here never resolves through
+# the user's global flake registry (every call targets this repo's own
+# flake, or an explicit github: ref, not a registry alias); --no-accept-flake-config
+# so a flake input's own nixConfig (e.g. a dependency's substituters) is
+# never honored -- matches accept-flake-config = false already set repo-wide
+# (see lib/nix-bootstrap.sh / CLAUDE.md). Reuse this array rather than
+# retyping the two flags at each call site.
+declare -a NIX_EVAL_FLAGS=(--no-use-registries --no-accept-flake-config)
+
+# list_flake_targets <flake_ref>
+# Prints the attribute names under <flake_ref>#nixosConfigurations, one per
+# line, e.g.:
+#   list_flake_targets .            # from inside the repo
+#   list_flake_targets "$repo_root" # from anywhere
+list_flake_targets() {
+  local flake_ref="$1"
+  nix eval --json "${NIX_EVAL_FLAGS[@]}" \
+    "${flake_ref}#nixosConfigurations" --apply builtins.attrNames \
+  | jq -r '.[]'
+}
+
+# flake_target_hostname <flake_ref> <target>
+# Prints one nixosConfigurations target's config.networking.hostName.
+# Empty (not an error under set -e) if the target doesn't exist or the
+# eval otherwise fails -- callers that need to distinguish "empty" from
+# "eval failed" should check $? themselves instead of relying on this.
+flake_target_hostname() {
+  local flake_ref="$1" target="$2"
+  nix eval --raw "${NIX_EVAL_FLAGS[@]}" \
+    "${flake_ref}#nixosConfigurations.${target}.config.networking.hostName" 2>/dev/null
+}

scripts/lib/ssh-host-keys.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Shared SSH-host-key / age-conversion helpers for scripts/sync-host-keys.sh
+# and scripts/prepare-host-key.sh -- both generate the same kind of key
+# (ed25519, no passphrase, the sops-nix age-derivation input) and convert it
+# to an age recipient the same way; kept in one place so the two can't
+# drift apart.
+#
+# Uses NIX_OPTS (an array of extra `nix-shell` options -- see env.sh's
+# nix_extra_opts) if the caller has already set it, so a decision to avoid
+# an unreachable nix-cache is reused here instead of probed again. Falls
+# back to no extra options if the caller never sourced env.sh.
+if ! declare -p NIX_OPTS >/dev/null 2>&1; then
+  declare -a NIX_OPTS=()
+fi
+
+# generate_host_ed25519_key <hostname> <keyfile>
+# Writes <keyfile> and <keyfile>.pub. Caller is responsible for refusing to
+# overwrite an existing keyfile -- this always runs ssh-keygen fresh.
+generate_host_ed25519_key() {
+  local hostname="$1" keyfile="$2"
+  nix-shell "${NIX_OPTS[@]}" -p openssh --run \
+    "ssh-keygen -t ed25519 -N '' -C '${hostname}' -f '${keyfile}'" >/dev/null
+}
+
+# ssh_pubkey_to_age <pubkeyfile>
+# Prints the age public key derived from an ed25519 SSH public key file.
+ssh_pubkey_to_age() {
+  local pubkeyfile="$1"
+  nix-shell "${NIX_OPTS[@]}" -p ssh-to-age --run "ssh-to-age -i '${pubkeyfile}'"
+}

scripts/prepare-host-key.sh

@@ -23,6 +23,10 @@
 set -euo pipefail
 
 repo_root="$(cd "$(dirname "$0")/.." && pwd)"
+# shellcheck source=env.sh
+source "${repo_root}/scripts/env.sh"
+# shellcheck source=lib/ssh-host-keys.sh
+source "${repo_root}/scripts/lib/ssh-host-keys.sh"
 
 hostname="${1:?usage: scripts/prepare-host-key.sh <hostname>}"
 sops_yaml="${repo_root}/.sops.yaml"
@@ -41,9 +45,10 @@ if [[ -f "$keyfile" ]]; then
   exit 1
 fi
 
-nix-shell -p openssh --run "ssh-keygen -t ed25519 -N '' -C '${hostname}' -f '${keyfile}'" >/dev/null
+nix_extra_opts
+generate_host_ed25519_key "$hostname" "$keyfile"
 
-age_pub="$(nix-shell -p ssh-to-age --run "ssh-to-age -i '${keyfile}.pub'")"
+age_pub="$(ssh_pubkey_to_age "${keyfile}.pub")"
 
 cat <<EOF
 

scripts/sync-host-keys.sh

@@ -31,6 +31,10 @@ editor="${repo_root}/scripts/lib/sync-host-keys-edit-sops.py"
 
 # shellcheck source=env.sh
 source "${repo_root}/scripts/env.sh"
+# shellcheck source=lib/nix-eval.sh
+source "${repo_root}/scripts/lib/nix-eval.sh"
+# shellcheck source=lib/ssh-host-keys.sh
+source "${repo_root}/scripts/lib/ssh-host-keys.sh"
 
 mkdir -p "$keydir"
 
@@ -118,12 +122,10 @@ EOF
 }
 
 discover_targets() {
-  nix eval --json --no-use-registries --no-accept-flake-config \
-    "${repo_root}#nixosConfigurations" --apply builtins.attrNames \
-  | jq -r '.[] | select(. != "installer")'
   # installer is the one nixosConfigurations target that doesn't import
   # sops-nix at all (see CLAUDE.md's "Security Notes" -- hardcoded login
   # password instead) -- config.sops.secrets doesn't exist for it.
+  list_flake_targets "$repo_root" | grep -v '^installer$'
 }
 
 locally_managed_hosts() {
@@ -159,7 +161,7 @@ queue_host_sync() {
       echo "[dry-run] ${host}: would generate host key"
     else
       echo "==> ${host}: generating host key"
-      nix-shell "${NIX_OPTS[@]}" -p openssh --run "ssh-keygen -t ed25519 -N '' -C '${host}' -f '${keyfile}'" >/dev/null
+      generate_host_ed25519_key "$host" "$keyfile"
     fi
   else
     echo "==> ${host}: host key already present"
@@ -170,7 +172,7 @@ queue_host_sync() {
     if [[ "$dry_run" -eq 1 ]]; then
       age_pub="dry-run-placeholder-not-a-real-key"
     else
-      age_pub="$(nix-shell "${NIX_OPTS[@]}" -p ssh-to-age --run "ssh-to-age -i '${keyfile}.pub'")"
+      age_pub="$(ssh_pubkey_to_age "${keyfile}.pub")"
     fi
     add_keys_json="$(jq --arg host "$host" --arg key "$age_pub" \
       '. + [{host: $host, age_key: $key}]' <<<"$add_keys_json")"