security: version the CIS Tier-A hardening pass

The script that sets the SSH, PAM, pwquality and auditd baseline on twelve
containers existed only as a root-owned copy on the machines it hardens.
Bring it into the repo so a change reaches one place instead of twelve.

Two substantive changes over the copy that shipped on 2026-07-24:

- Deny forwarding per option instead of via DisableForwarding. Same effect,
  but DisableForwarding overrides every other forwarding option and is
  invisible in sshd -T, which makes a rejected port-forward read as a
  configuration that should work.
- Quote the command substitution in MODDIR (SC2046).

The header and README now record the rollout command, the containers left
unhardened as break-glass foundation, and why host-specific exceptions must
live in a drop-in that sorts after 99-cis-hardening.conf.

README.md

@@ -41,6 +41,8 @@ Two files per app, both sourcing the shared libs via `curl`:
 - **`ct/<app>.sh`** runs on the PVE host: prompts → unprivileged LXC → pushes a config env file into the container → bootstraps the installer. Apps that need Docker (authentik, runner) enable `nesting+keyctl` automatically. The standard prompts include an **SSH root login choice** (`SSH_ROOT_LOGIN`, default yes for homelab convenience; `no` keeps the Debian key-only default) — applied inside the container as an sshd drop-in by `configure_ssh_root_login`.
 - **`install/<app>-install.sh`** runs inside the LXC: packages, unprivileged app user, secrets generated on-host (never printed), systemd units, a `/root/<app>.credentials` notes file — then shreds the bootstrap env. Idempotent where it matters: re-runs skip what exists. `setup_base_apt` also fixes the bare-template **locale situation**: `C.UTF-8` is exported up front (glibc built-in, covers the first apt run without perl warnings), then `en_US.UTF-8` is generated and set as the system default.
 
+**DB installers** carry one extra rule: a PostgreSQL cluster/database freezes its encoding at initdb / `CREATE DATABASE` time and it can never be changed afterwards. A C (non-UTF-8) locale yields a `SQL_ASCII` cluster — psycopg3 then hands text back as bytes and SQLAlchemy crashes. So the pattern (helpers `ensure_utf8_locale_active` + `assert_db_encoding_utf8` in `lib/install.func`) is: make a UTF-8 locale **active** before the server package runs initdb, create the database **explicitly** with `TEMPLATE template0 ENCODING 'UTF8' LC_COLLATE/LC_CTYPE 'en_US.UTF-8'` (never inherit the cluster default), and **verify** `pg_encoding_to_char` returns `UTF8` before finishing — a wrong encoding aborts the install (it's DB damage, see wiki → Lessons). Maintenance examples use `su - postgres -c …`, not `sudo` — these minimal LXCs have no sudo.
+
 Shared libs: [`lib/build.func`](lib/build.func) (host-side: prompts, LXC create, bootstrap) and [`lib/install.func`](lib/install.func) (in-container: apt, users, systemd, http-wait).
 
 ## Security conventions
@@ -50,6 +52,24 @@ Shared libs: [`lib/build.func`](lib/build.func) (host-side: prompts, LXC create,
 - Secrets are generated on the target host and live in `0600` files — never in the repo, the wiki or chat logs.
 - **Runner separation:** the nexus runner is repo-scoped and lives on the production LXC *because* it holds deploy rights; the general `runner` LXC is instance-wide *because* it holds none. Don't mix these scopes.
 
+### CIS Tier-A hardening
+
+[`install/cis-tierA.sh`](install/cis-tierA.sh) applies the Tier-A baseline to an existing Debian 12 LXC: SSH drop-in, `login.defs` aging + YESCRYPT, pwquality/faillock, PAM (pwquality, pwhistory, faillock, `nullok` removed) and auditd rules. It is idempotent, backs everything up to `/root/cis-hardening-backup-<ts>/`, gates the SSH restart on `sshd -t` and rolls PAM back if a referenced module is missing.
+
+```bash
+pct push <id> install/cis-tierA.sh /root/cis-tierA.sh
+pct exec <id> -- bash /root/cis-tierA.sh
+```
+
+Applied to authentik first (2026-07-24), then to 11 further containers. The PVE hosts and the Wazuh manager VM stay unhardened on purpose — they are the break-glass foundation.
+
+Two things worth knowing before touching it:
+
+- **Section 1 rewrites `99-cis-hardening.conf` wholesale on every run.** Host-specific exceptions belong in a separate drop-in that sorts *after* it (e.g. `99-zz-local-forward.conf`), never in that file. A `Match` block extends until the next `Match` — across `Include` file boundaries — so such a drop-in has to stay alphabetically last.
+- **Forwarding is denied per option, not via `DisableForwarding`.** Both are equivalent in effect, but `DisableForwarding` overrides every other forwarding option *and* does not appear in `sshd -T` output. A denied port-forward then reports `administratively prohibited` while `sshd -T` cheerfully claims `allowtcpforwarding yes`, which costs hours to diagnose.
+
+Caveat: auditd is a no-op in unprivileged LXCs (the host owns the audit subsystem); the script probes for it and removes the package again if it cannot load rules. Together with the Section-1 partition/kernel checks that are equally N/A in a container, the achievable SCA score stays well below 100 %.
+
 ## Contributing
 
 **All changes go through a pull request with cross-review** (Claude Code ↔ Codex, or a human) — no direct pushes to `main`. This rule exists because of two real incidents: a pasted VLAN tag carrying an invisible non-UTF-8 byte broke `pct create` mid-run, and the "missing `source build.func`" bug shipped twice — caught in review on the nexus-db PR, but reaching production via an un-reviewed authentik commit (see wiki → Lessons).
@@ -63,7 +83,8 @@ Build new app prompts on `prompt_validated`/`require_valid` from `lib/build.func
 ```
 .
 ├── ct/                 # Host-side scripts, one per app
-├── install/            # In-container installers (+ nexus-runtime.sh re-provisioner)
+├── install/            # In-container installers (+ nexus-runtime.sh re-provisioner,
+│                       #   cis-tierA.sh hardening pass)
 ├── lib/
 │   ├── build.func      # Shared host-side helpers (prompts, LXC create, bootstrap)
 │   └── install.func    # Shared in-container helpers (apt, systemd, users, http-wait)

install/cis-tierA.sh

@@ -0,0 +1,163 @@
+#!/bin/bash
+# CIS Tier-A hardening for a Debian 12 LXC. Idempotent, backs up everything,
+# gates the SSH restart on `sshd -t`, auto-rolls-back PAM on sanity failure.
+# Recovery path if anything breaks: `pct exec <id> -- bash` from the PVE host.
+#
+# Rollout: copy into the target LXC and run as root, e.g.
+#   pct push <id> install/cis-tierA.sh /root/cis-tierA.sh
+#   pct exec <id> -- bash /root/cis-tierA.sh
+# First applied to authentik on 2026-07-24, then to 11 further containers.
+#
+# NOT hardened on purpose (break-glass foundation): the PVE hosts pve-gamer /
+# pve-i5 and the Wazuh manager VM. See the wiki for the break-glass chain.
+#
+# SSH: section 1 rewrites /etc/ssh/sshd_config.d/99-cis-hardening.conf WHOLESALE
+# on every run. Host-specific exceptions therefore do NOT belong in that file —
+# put them in a separate drop-in that sorts AFTER it, e.g.
+# 99-zz-local-forward.conf. Mind that a Match block extends until the next
+# Match, across Include file boundaries, so such a drop-in must stay last.
+#
+# Forwarding is denied per option (AllowTcpForwarding / AllowAgentForwarding /
+# AllowStreamLocalForwarding / X11Forwarding), not via DisableForwarding. Both
+# are equivalent in effect, but DisableForwarding overrides every other
+# forwarding option AND is invisible in `sshd -T` output — which makes a denied
+# port-forward practically undiagnosable. See the wiki entry on that.
+set -u
+TS=$(date +%Y%m%d-%H%M%S)
+BK=/root/cis-hardening-backup-$TS
+mkdir -p "$BK"
+export DEBIAN_FRONTEND=noninteractive
+say(){ echo "[cis] $*"; }
+
+########## 1. SSH hardening (drop-in, validated) ##########
+SSHD=/etc/ssh/sshd_config.d/99-cis-hardening.conf
+grep -q "Include /etc/ssh/sshd_config.d" /etc/ssh/sshd_config || echo "Include /etc/ssh/sshd_config.d/*.conf" > /tmp/_noinc
+[ -f "$SSHD" ] && cp "$SSHD" "$BK/" 2>/dev/null
+printf '%s\n' "Warning: Authorized access only. All activity is monitored." > /etc/issue.net
+cat > "$SSHD" <<'EOF'
+PermitRootLogin prohibit-password
+MaxAuthTries 4
+LoginGraceTime 60
+ClientAliveInterval 15
+ClientAliveCountMax 3
+Banner /etc/issue.net
+MaxStartups 10:30:60
+AllowTcpForwarding no
+AllowAgentForwarding no
+AllowStreamLocalForwarding no
+X11Forwarding no
+Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
+MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com
+KexAlgorithms curve25519-sha256,curve25519-sha256@libssh.org,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512
+EOF
+if sshd -t 2>/tmp/sshderr; then
+  systemctl restart ssh 2>/dev/null || systemctl restart sshd 2>/dev/null
+  say "SSH: drop-in applied + restarted (sshd -t OK, active=$(systemctl is-active ssh 2>/dev/null || systemctl is-active sshd 2>/dev/null))"
+else
+  rm -f "$SSHD"; say "SSH: sshd -t FAILED -> reverted ($(cat /tmp/sshderr))"
+fi
+
+########## 2. login.defs (password aging + hashing) ##########
+cp /etc/login.defs "$BK/"
+setdef(){ if grep -qE "^\s*$1\b" /etc/login.defs; then sed -i -E "s|^\s*$1\b.*|$1 $2|" /etc/login.defs; else echo "$1 $2" >> /etc/login.defs; fi; }
+setdef PASS_MAX_DAYS 365
+setdef PASS_MIN_DAYS 1
+setdef PASS_WARN_AGE 7
+setdef ENCRYPT_METHOD YESCRYPT
+useradd -D -f 30 2>/dev/null
+say "login.defs: aging + YESCRYPT set"
+
+########## 3. pwquality ##########
+apt-get install -y libpam-pwquality >/dev/null 2>&1
+[ -f /etc/security/pwquality.conf ] && cp /etc/security/pwquality.conf "$BK/"
+cat > /etc/security/pwquality.conf <<'EOF'
+minlen = 14
+minclass = 4
+maxrepeat = 3
+dictcheck = 1
+enforcing = 1
+EOF
+[ -f /etc/security/faillock.conf ] && cp /etc/security/faillock.conf "$BK/"
+cat > /etc/security/faillock.conf <<'EOF'
+deny = 5
+unlock_time = 900
+fail_interval = 900
+EOF
+say "pwquality.conf + faillock.conf written"
+
+########## 4. PAM module enablement (backup + sanity + rollback) ##########
+CA=/etc/pam.d/common-auth
+CP=/etc/pam.d/common-password
+cp "$CA" "$BK/"; cp "$CP" "$BK/"
+
+# 5.3.3.4.1 remove nullok
+sed -i 's/[[:space:]]*nullok//g' "$CA" "$CP"
+
+# common-password: full, correctly-formed pwquality + pwhistory lines before pam_unix
+grep -q pam_pwquality.so "$CP" || sed -i '0,/^password[[:space:]].*pam_unix.so/s//password requisite pam_pwquality.so retry=3\n&/' "$CP"
+grep -q pam_pwhistory.so "$CP" || sed -i '0,/^password[[:space:]].*pam_unix.so/s//password required pam_pwhistory.so remember=5 use_authtok\n&/' "$CP"
+grep -qE 'pam_unix.so.*use_authtok' "$CP" || sed -i -E 's/(^password[[:space:]].*pam_unix.so.*)/\1 use_authtok/' "$CP"
+
+# common-auth: faillock preauth/authfail/authsucc (full lines, idempotent)
+if ! grep -q pam_faillock.so "$CA"; then
+  sed -i '1i auth required pam_faillock.so preauth' "$CA"
+  awk 'BEGIN{d=0}{print} (/pam_unix.so/ && d==0){print "auth [default=die] pam_faillock.so authfail"; print "auth sufficient pam_faillock.so authsucc"; d=1}' "$CA" > "$CA.tmp" && mv "$CA.tmp" "$CA"
+fi
+
+# sanity: every referenced module must exist; pam_unix + pam_deny must remain
+MODDIR=$(dirname "$(find /lib /usr/lib -name pam_unix.so 2>/dev/null | head -1)")
+ok=1
+for m in $(grep -hoE 'pam_[a-z_]+\.so' "$CA" "$CP" | sort -u); do
+  [ -f "$MODDIR/$m" ] || { say "PAM sanity: missing $m"; ok=0; }
+done
+grep -q pam_unix.so "$CA" && grep -q pam_unix.so "$CP" || ok=0
+if [ "$ok" != "1" ]; then
+  cp "$BK/common-auth" "$CA"; cp "$BK/common-password" "$CP"
+  say "PAM: sanity FAILED -> rolled back common-auth/common-password"
+else
+  say "PAM: pwquality/pwhistory/faillock enabled, nullok removed (sanity OK)"
+fi
+
+########## 5. auditd (probe LXC support) ##########
+apt-get install -y auditd audispd-plugins >/dev/null 2>&1
+AUOK=0
+if auditctl -l >/dev/null 2>&1 && auditctl -a always,exit -F arch=b64 -S adjtimex -k _probe 2>/dev/null; then
+  auditctl -d always,exit -F arch=b64 -S adjtimex -k _probe 2>/dev/null; AUOK=1
+fi
+if [ "$AUOK" = "1" ]; then
+  cp -n /etc/audit/rules.d/audit.rules "$BK/" 2>/dev/null
+  cat > /etc/audit/rules.d/cis.rules <<'EOF'
+-w /etc/group -p wa -k identity
+-w /etc/passwd -p wa -k identity
+-w /etc/shadow -p wa -k identity
+-w /etc/gshadow -p wa -k identity
+-w /etc/security/opasswd -p wa -k identity
+-w /etc/sudoers -p wa -k scope
+-w /etc/sudoers.d/ -p wa -k scope
+-w /var/log/sudo.log -p wa -k sudo_log
+-a always,exit -F arch=b64 -S adjtimex,settimeofday,clock_settime -k time-change
+-a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale
+-w /etc/hosts -p wa -k system-locale
+-w /etc/network/ -p wa -k system-locale
+-w /var/log/wtmp -p wa -k session
+-w /var/log/btmp -p wa -k session
+-w /var/run/utmp -p wa -k session
+-w /var/log/lastlog -p wa -k logins
+-w /var/run/faillock/ -p wa -k logins
+-a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=4294967295 -k mounts
+-a always,exit -F arch=b64 -S unlink,unlinkat,rename,renameat -F auid>=1000 -F auid!=4294967295 -k delete
+-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chown,fchown,fchownat,lchown -F auid>=1000 -F auid!=4294967295 -k perm_mod
+-a always,exit -F arch=b64 -S init_module,delete_module,finit_module -k modules
+-w /usr/sbin/usermod -p x -k usermod
+EOF
+  systemctl enable auditd >/dev/null 2>&1
+  augenrules --load >/dev/null 2>&1
+  systemctl restart auditd 2>/dev/null || service auditd restart 2>/dev/null
+  say "auditd: FUNCTIONAL in this LXC -> CIS rules loaded ($(auditctl -l 2>/dev/null | wc -l) rules)"
+else
+  systemctl disable --now auditd >/dev/null 2>&1
+  apt-get purge -y auditd audispd-plugins >/dev/null 2>&1
+  say "auditd: NOT supported in this LXC (host owns audit subsystem) -> N/A, removed"
+fi
+
+say "DONE. Backup: $BK"

install/nexus-db-install.sh

@@ -47,6 +47,12 @@ else
   msg_warn "PGDG repo already present, skipping"
 fi
 
+# The server package runs initdb for the `main` cluster on install — its
+# encoding is frozen there. Make a UTF-8 locale active for THIS process first
+# so the cluster is never created as SQL_ASCII (issue #8: a pre-fix LXC was
+# provisioned under LANG=C and ended up SQL_ASCII).
+ensure_utf8_locale_active en_US.UTF-8
+
 msg_info "Installing PostgreSQL $PG_MAJOR + pgvector..."
 apt-get install -y -qq "postgresql-$PG_MAJOR" "postgresql-$PG_MAJOR-pgvector" >/dev/null
 msg_ok "PostgreSQL $(psql --version | awk '{print $3}') installed"
@@ -95,6 +101,13 @@ systemctl restart postgresql
 # ── role + database + extension (idempotent, password kept on re-run) ─────────
 run_psql() { runuser -u postgres -- psql -v ON_ERROR_STOP=1 -qAt "$@"; }
 
+# Re-run safety (issue #8): if the database already exists, verify its
+# encoding BEFORE touching roles/passwords. An old SQL_ASCII database must
+# abort the run with NO side effects — not after rotating credentials.
+if [[ "$(run_psql -c "SELECT 1 FROM pg_database WHERE datname='$DB_NAME'")" == "1" ]]; then
+  assert_db_encoding_utf8 "$DB_NAME"
+fi
+
 if [[ "$(run_psql -c "SELECT 1 FROM pg_roles WHERE rolname='$DB_USER'")" != "1" ]]; then
   msg_info "Creating role $DB_USER + database $DB_NAME..."
   DB_PASS="$(openssl rand -base64 32 | tr -d '/+=' | head -c 32)"
@@ -114,12 +127,18 @@ else
 fi
 
 if [[ "$(run_psql -c "SELECT 1 FROM pg_database WHERE datname='$DB_NAME'")" != "1" ]]; then
-  run_psql -c "CREATE DATABASE $DB_NAME OWNER $DB_USER"
+  # Explicit encoding/collation from template0 — never inherit the cluster
+  # default, which may be SQL_ASCII if initdb ran under a broken locale
+  # (issue #8). template0 is required to override LC_COLLATE/LC_CTYPE.
+  run_psql -c "CREATE DATABASE $DB_NAME OWNER $DB_USER ENCODING 'UTF8' LC_COLLATE 'en_US.UTF-8' LC_CTYPE 'en_US.UTF-8' TEMPLATE template0"
   # Only the owner may connect — no PUBLIC access.
   run_psql -c "REVOKE CONNECT ON DATABASE $DB_NAME FROM PUBLIC"
-  msg_ok "Database $DB_NAME created (owner $DB_USER, PUBLIC revoked)"
+  # Verify what we just created (the pre-existing case was already checked
+  # before the role block, issue #8).
+  assert_db_encoding_utf8 "$DB_NAME"
+  msg_ok "Database $DB_NAME created (UTF8, owner $DB_USER, PUBLIC revoked)"
 else
-  msg_warn "Database $DB_NAME already exists, skipping"
+  msg_warn "Database $DB_NAME already exists, skipping creation"
 fi
 
 # pgvector: CREATE EXTENSION needs superuser; installed now (per ADR-0002:
@@ -141,9 +160,12 @@ Password: $DB_PASS
 DSN for /etc/nexus/env on the nexus LXC (NEXUS_DATABASE_URL):
   postgresql+psycopg://$DB_USER:$DB_PASS@$IP_SELF:$DB_PORT/$DB_NAME
 
+Encoding: UTF8 (LC_COLLATE/LC_CTYPE en_US.UTF-8) — verified at install time.
+
 Access policy (pg_hba): only $NEXUS_APP_IP/32 may connect; all other
-hosts are rejected. Local socket stays peer-auth for maintenance:
-  pct exec <CTID> -- runuser -u postgres -- psql -d $DB_NAME
+hosts are rejected. Local socket stays peer-auth for maintenance (these
+minimal LXCs have no sudo — use su, not sudo):
+  pct exec <CTID> -- su - postgres -c "psql -d $DB_NAME"
 EOF
   chmod 600 "$CRED_FILE"
   msg_ok "Credentials written to $CRED_FILE (chmod 600)"

install/runner-install.sh

@@ -63,8 +63,34 @@ valid_token_word "$RUNNER_LABELS" || { msg_err "RUNNER_LABELS enthält unzuläss
 # der unprivilegierte User darf dort nicht schreiben.
 run_user() { runuser -u "$APP_USER" -- env -C "$RUNNER_DIR" HOME="$APP_HOME" "$@"; }
 
-# ── Pakete: git/rsync, Node (checkout-Action), Docker (Test-Container) ────────
-setup_base_apt git rsync ca-certificates curl
+# ── Pakete: git/rsync, Node (checkout-Action), Docker (Test-Container),
+#    Build-Werkzeuge (Compiler-Sprachen in CI) ─────────────────────────────────
+#
+# make/gcc/protobuf: Der Runner faehrt Host-Mode, also gibt es kein Image, das
+# Werkzeuge mitbringt — was hier nicht liegt, hat kein Job. Konkret gemessen an
+# l.kirchner/patchmgr (Go):
+#   make                 "make: command not found" in jedem Gate-Job
+#   gcc                  ohne gefundenen C-Compiler bleibt cgo aus (go env
+#                        meldet dann CGO_ENABLED=0), und "go test -race" ist
+#                        nicht baubar
+#   protobuf-compiler    protoc fuer die Codegenerierung
+#   libprotobuf-dev      liefert /usr/include/google/protobuf/*.proto; ohne die
+#                        Includes scheitert protoc trotz vorhandenem Binary
+#
+# ACHTUNG protoc: Das bindet jedes Repo der Instanz an die protoc-Fassung der
+# Distribution (Debian 12: 3.21.x). Anders als make/gcc ist protoc ein
+# Codegenerator — ein Distro-Upgrade aendert erzeugten Code fuer alle Nutzer
+# gleichzeitig. Wer eine eigene Fassung braucht, pinnt sie im Projekt
+# (Release-Tarball, buf, oder Docker — der Runner hat Docker) statt sie hier
+# zu heben.
+#
+# Bewusst NICHT installiert: sudo. Ein Workflow soll auf diesem Runner nichts
+# nachinstallieren koennen — was gebraucht wird, steht hier.
+#
+# Go selbst gehoert nicht hierher: Projekte holen es ueber actions/setup-go,
+# weil CI-Matrizen mehrere Fassungen fahren.
+setup_base_apt git rsync ca-certificates curl \
+  make gcc protobuf-compiler libprotobuf-dev
 
 NODE_HAVE="$(command -v node >/dev/null 2>&1 && node -v | sed -E 's/^v([0-9]+).*/\1/' || echo 0)"
 if [[ "$NODE_HAVE" != "$NODE_MAJOR" ]]; then

lib/install.func

@@ -54,6 +54,60 @@ apt_cleanup() {
   apt-get autoclean -qq >/dev/null || true
 }
 
+# ── database installers: UTF-8 locale before initdb ──────────────────────────
+# Pattern for every DB installer. A PostgreSQL cluster/database freezes its
+# encoding at initdb / CREATE DATABASE time and it cannot be changed later —
+# a C (non-UTF-8) locale yields a SQL_ASCII cluster. psycopg3 then returns
+# text as bytes and SQLAlchemy crashes on server-version detection; the app
+# reports "db: unreachable". So: GENERATE the UTF-8 locale AND make it active
+# for THIS process before the server package runs its automatic initdb, then
+# fail loudly if it is not actually available (generating alone is not enough
+# — the locale must be active when initdb runs).
+# Generates+activates a UTF-8 locale (default en_US.UTF-8); the argument
+# honours other UTF-8 locales consistently (match, locale.gen line and the
+# exported value all derive from it). Matching normalises case and dashes so
+# the canonical `en_US.UTF-8` matches `locale -a`'s `en_US.utf8`.
+ensure_utf8_locale_active() {
+  local loc="${1:-en_US.UTF-8}"
+  local norm; norm="$(printf '%s' "$loc" | tr 'A-Z' 'a-z' | tr -d '-')"
+  _locale_present() { locale -a 2>/dev/null | tr 'A-Z' 'a-z' | tr -d '-' | grep -qx "$norm"; }
+  msg_info "Ensuring $loc is generated and active (DB encoding is frozen at initdb)..."
+  if ! _locale_present; then
+    # Uncomment the matching `# <loc> UTF-8` line, then generate.
+    sed -i "s/^# *${loc} UTF-8/${loc} UTF-8/" /etc/locale.gen
+    locale-gen >/dev/null
+  fi
+  if ! _locale_present; then
+    msg_err "Locale $loc not available after locale-gen — refusing to continue (initdb would create a SQL_ASCII cluster)"
+    return 1
+  fi
+  # Activate for the current process so any automatic initdb during the
+  # server package install inherits a UTF-8 locale, not the bare-template C.
+  export LANG="$loc" LC_ALL="$loc"
+  msg_ok "Locale active for initdb: LANG=$LANG"
+}
+
+# Post-install guard: a database MUST be UTF8. Encoding is irreversible, so a
+# wrong value is database damage — abort with a clear, actionable message
+# instead of shipping a broken cluster. Uses argv-clean `runuser ... psql`
+# with a quoted :'db' literal binding (robust regardless of caller); the
+# credentials/README docs use `su - postgres -c` for hand maintenance (these
+# minimal LXCs have no sudo).
+assert_db_encoding_utf8() {
+  local db="$1" enc
+  enc="$(runuser -u postgres -- psql -X -qAt -v db="$db" \
+    -c "SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = :'db'")"
+  if [[ "$enc" != "UTF8" ]]; then
+    msg_err "Database '$db' has encoding '${enc:-<not found>}', expected UTF8."
+    msg_err "Encoding is frozen at creation time — this is DB damage, not cosmetic."
+    msg_err "Fix: regenerate the locale (locale-gen en_US.UTF-8) and recreate the DB"
+    msg_err "     with: CREATE DATABASE $db ... TEMPLATE template0 ENCODING 'UTF8'"
+    msg_err "          LC_COLLATE 'en_US.UTF-8' LC_CTYPE 'en_US.UTF-8';"
+    return 1
+  fi
+  msg_ok "Encoding check: database '$db' is UTF8"
+}
+
 # ── ssh ──────────────────────────────────────────────────────────────────────
 # SSH-Root-Login gemäß Host-Prompt (prompt_lxc_config setzt SSH_ROOT_LOGIN,
 # bootstrap_install_script reicht es als Env durch; Default: yes).