nixos/scripts/env.sh

#!/usr/bin/env bash
# Shared config for scripts/*.sh. Source this instead of hardcoding a
# second copy of these values in every script:
#   source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/env.sh"
# Every variable can still be overridden per-invocation via the
# environment (e.g. PROXMOX_STORAGE=tank-nvme ./scripts/create-proxmox-resource.sh ...)
# since each one only sets a default if unset.

# SSH-reachable Proxmox node that scripts/create-proxmox-resource.sh runs
# pct/qm on. Matches the Proxmox web UI hostname already used in
# hosts/nixos/home.nix's desktop shortcuts (pve.<homeDomain> from
# variables.nix) -- change this if that's not actually reachable over SSH,
# or if you're targeting a different node in a multi-node cluster.
: "${PROXMOX_HOST:=pve.sweet.home}"
: "${PROXMOX_SSH_USER:=root}"

# Storage pool names -- Proxmox's own stock-install defaults, but this
# varies a lot by setup (ZFS pool name, custom LVM-thin volume, etc.).
# Verify with `pvesm status` on the node and correct these if wrong.
: "${PROXMOX_STORAGE:=local-lvm}"     # VM disks / CT rootfs
: "${PROXMOX_ISO_STORAGE:=local}"     # uploaded images/ISOs/CT templates

: "${PROXMOX_BRIDGE:=vmbr0}"

# Fallback resource sizing when a script doesn't get --cores/--memory.
: "${PROXMOX_DEFAULT_CORES:=2}"
: "${PROXMOX_DEFAULT_MEMORY_MB:=2048}"

# `pct create` (unlike `pct restore`) requires an explicit rootfs size --
# no backup metadata to infer it from. Matches Proxmox's own GUI default.
: "${PROXMOX_DEFAULT_LXC_DISK_GB:=8}"

# `pct create --memory` only sets RAM -- swap is a wholly separate
# parameter that otherwise silently stays at Proxmox's own 512M default
# regardless of --memory (confirmed: creating with --memory 2048 left
# swap at 512). create-proxmox-resource.sh defaults --swap to whatever
# --memory resolves to at runtime rather than a static value here, so it
# tracks a --memory picked at the CLI too, not just the default above.

# Required for a modern (v247+) systemd guest to actually boot as an
# unprivileged container: systemd's routine use of nested user namespaces
# and credential mounts (LoadCredential=, DynamicUser=, etc. -- used even
# by plain getty units) gets denied by AppArmor's default LXC confinement
# without these. Confirmed live: without them, every getty unit
# crash-loops on a denied `/run/credentials/*` mount every ~3s (visible
# as garbage on the console) and core services like nsncd fail the same
# way on userns_create; system.build.tarball never finishes activating.
: "${PROXMOX_DEFAULT_LXC_FEATURES:=nesting=1,keyctl=1}"

export PROXMOX_HOST PROXMOX_SSH_USER PROXMOX_STORAGE PROXMOX_ISO_STORAGE \
  PROXMOX_BRIDGE PROXMOX_DEFAULT_CORES PROXMOX_DEFAULT_MEMORY_MB \
  PROXMOX_DEFAULT_LXC_DISK_GB PROXMOX_DEFAULT_LXC_FEATURES

# Matches variables.nix's nixCacheHost -- update both if it ever changes.
: "${NIX_CACHE_HOST:=nix-cache}"
export NIX_CACHE_HOST

# nix_extra_opts: call as a plain statement (NOT inside $(...)/<(...) --
# that forks a subshell, and the whole point is exporting a decision back
# into *this* shell) to populate the global NIX_OPTS array with whatever
# extra `nix`/`nix-shell` CLI options are needed to avoid nix-cache when
# it's unreachable:
#   nix_extra_opts
#   nix build "${NIX_OPTS[@]}" ...
#
# Without this, every single `nix eval`/`nix build` call retries each
# store path against a dead substituter up to 5 times with backoff
# (confirmed: ~15s+ per lookup even with a short connect-timeout, because
# nix's own retry count isn't controllable that way), and separately
# tries it as a remote builder too -- both fail independently, so both
# are checked.
#
# Checked with a single fast `curl`/TCP probe (bypassing nix's retry logic
# entirely) the first time this is called in a given process, and the
# result is exported as NIX_EXTRA_OPTS so a script that shells out to
# another script in this repo (e.g. create-proxmox-resource.sh calling
# sync-host-keys.sh) reuses the same decision instead of probing twice.
declare -a NIX_OPTS=()

nix_extra_opts() {
  if [[ -n "${NIX_EXTRA_OPTS_DECIDED:-}" ]]; then
    if [[ -n "${NIX_EXTRA_OPTS:-}" ]]; then
      eval "NIX_OPTS=(${NIX_EXTRA_OPTS})"
    else
      NIX_OPTS=()
    fi
    return
  fi
  export NIX_EXTRA_OPTS_DECIDED=1
  NIX_OPTS=()

  # Retry a couple of times, 1s apart, before believing either check --
  # belt-and-suspenders against a genuine multi-second blip (nix-cache
  # restarting), on top of the fix below. Worst case (~11s total, host
  # genuinely gone) is still nowhere near the 15s+ *per lookup* nix's own
  # substituter retries would cost if this check didn't exist at all.
  local attempt cache_up=0 builder_up=0
  for attempt in 1 2 3; do
    if curl --silent --fail --max-time 3 "http://${NIX_CACHE_HOST}/nix-cache-info" >/dev/null 2>&1; then
      cache_up=1
      break
    fi
    [[ "$attempt" -lt 3 ]] && sleep 1
  done

  if [[ "$cache_up" -eq 0 ]]; then
    echo "nix-cache (http://${NIX_CACHE_HOST}) is unreachable -- skipping it (substituter + remote builder) for the rest of this run." >&2
    NIX_OPTS=(--option substituters "https://cache.nixos.org/" --builders "")
  else
    for attempt in 1 2 3; do
      # `exec 3<>/dev/tcp/...` just opens the fd and returns -- it does NOT
      # read from it. Confirmed live this is load-bearing, not stylistic:
      # the previous `cat < /dev/tcp/.../22` blocked forever and always hit
      # the timeout even against a perfectly healthy nix-cache, because
      # sshd sends its banner and then holds the connection open waiting
      # for the client to speak next -- `cat` never sees EOF, so this
      # check reported "unreachable" unconditionally, 100% of the time,
      # regardless of whether the remote builder was actually up.
      if timeout 3 bash -c "exec 3<>/dev/tcp/${NIX_CACHE_HOST}/22" 2>/dev/null; then
        builder_up=1
        break
      fi
      [[ "$attempt" -lt 3 ]] && sleep 1
    done
    if [[ "$builder_up" -eq 0 ]]; then
      echo "nix-cache's SSH remote builder (nixremote@${NIX_CACHE_HOST}:22) is unreachable -- disabling remote builds for the rest of this run." >&2
      NIX_OPTS=(--builders "")
    fi
  fi

  # `printf '%q '` with a genuinely empty NIX_OPTS still runs one format
  # pass over a missing argument and yields the literal `'' ` rather than
  # an empty string (confirmed live) -- a subprocess that later does
  # `eval "NIX_OPTS=(${NIX_EXTRA_OPTS})"` (the branch above, for e.g.
  # sync-host-keys.sh reusing this process's decision) would then rebuild
  # a 1-element array holding an empty string instead of a 0-element
  # array, and `nix-shell "${NIX_OPTS[@]}" -p <pkg>` chokes on that stray
  # element as a bogus positional argument. Guard the empty case
  # explicitly so nix-cache being reachable (NIX_OPTS legitimately empty)
  # round-trips as truly empty instead.
  if [[ ${#NIX_OPTS[@]} -gt 0 ]]; then
    printf -v NIX_EXTRA_OPTS '%q ' "${NIX_OPTS[@]}"
  else
    NIX_EXTRA_OPTS=""
  fi
  export NIX_EXTRA_OPTS
}