feat: integrate rollback sentinel as NixOS module

Add rollback-sentinel NixOS module that:
- Deploys sentinel-check.sh (inline) and nixos-rollback.sh (from file) as
  system packages
- Runs a boot-time systemd oneshot service after multi-user.target with
  configurable delay — checks Tier-1 services, triggers rollback on failure
- Runs a post-rebuild service via activation script after every
  nixos-rebuild switch
- Exposes options for tier1Services, tier2Services, tier3InfoServices,
  bootDelay, rollbackMode (set-default/rollback-now/dry-run), and
  enablePostRebuild

Module wired into flake.nix for lazyworkhorse and enabled in
configuration.nix with standard Tier-1/2 service lists and 120s delay.

flake.nix

@@ -61,6 +61,7 @@
               ./modules/nixos/services/open_code_server.nix
               ./modules/nixos/services/ollama_init_custom_models.nix
               ./modules/nixos/services/openclaw_node.nix
+              ./modules/nixos/services/rollback-sentinel.nix
               ./modules/nixos/security/ai-worker-restricted.nix
               ./users/gortium.nix
               ./users/ai-worker.nix

hosts/lazyworkhorse/configuration.nix

@@ -321,11 +321,41 @@
   environment.etc."ssh/ssh_host_ed25519_key.pub".text =
     "${keys.hosts.lazyworkhorse.main}";
 
+  # ── Boot sentinel: auto-rollback on critical service failure ───────────────
+  services.rollbackSentinel.enable = true;
+  # Tier-1: failure triggers rollback
+  services.rollbackSentinel.tier1Services = [
+    "sshd" "docker" "traefik" "authelia"
+  ];
+  # Tier-2: warn only
+  services.rollbackSentinel.tier2Services = [
+    "gitea" "hermes" "ollama" "synapse" "nextcloud"
+    "vaultwarden" "wireguard" "homeassistant" "fail2ban"
+  ];
+  # Wait 2 minutes after boot before checking (lets services initialize)
+  services.rollbackSentinel.bootDelay = "120";
+  # Change boot default only (not --rollback-now) for safety
+  services.rollbackSentinel.rollbackMode = "set-default";
+
   services.fstrim.enable = true;
 
   services.zfs.autoSnapshot.enable = true;
   services.zfs.autoScrub.enable = true;
 
+  # Ensure com.sun:auto-snapshot is set on ZFS datasets so auto-snapshots actually run
+  systemd.services."zfs-set-auto-snapshot" = {
+    description = "Set com.sun:auto-snapshot=true on ZFS datasets";
+    after = [ "zfs-import.target" ];
+    wants = [ "zfs-import.target" ];
+    wantedBy = [ "multi-user.target" ];
+    path = with pkgs; [ zfs ];
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+      ExecStart = "${pkgs.zfs}/bin/zfs set -r com.sun:auto-snapshot=true rpool";
+    };
+  };
+  
   # Mi50 config
   hardware.graphics = {
     enable = true;

modules/nixos/security/README-ai-worker.md

@@ -1,44 +1,10 @@
 # AI Worker Restricted Access
 
-This module provides SSH access for the AI worker (hermes-agent) to run docker commands on the host.
+This module provides SSH access for the AI worker (hermes-agent) to run ollama benchmarks on the host.
 
 ## Security Model
 
-### Overview
+The `ai-worker` user has:
-
-The `ai-worker` user has **no direct docker group access**. All docker commands must go through `sudo`, and only specific subcommands are whitelisted:
-
-- **Container lifecycle**: `docker ps`, `docker inspect`, `docker logs`, `docker images`, `docker info`, `docker version`, `docker stats`
-- **Control**: `docker start`, `docker stop`, `docker restart`, `docker rm`, `docker rmi`, `docker wait`
-- **Image management**: `docker pull`, `docker build`, `docker run`, `docker compose`
-- **Disk cleanup**: `docker system`
-- **Network/Volume**: `docker network ls`, `docker volume ls` (read-only)
-
-### EXPLICITLY BLOCKED (not in sudo whitelist)
-
-| Command | Risk | Result |
-|---------|------|--------|
-| `docker exec` | Execute arbitrary commands inside containers (FILE MODIFICATION) | Blocked by sudo |
-| `docker cp` | Copy files between containers and host | Blocked by sudo |
-| `docker commit` | Create images from running containers (data exfil) | Blocked by sudo |
-| `docker diff` | Inspect filesystem changes | Blocked by sudo |
-| `docker export` | Export container filesystem | Blocked by sudo |
-| `docker import` | Import filesystem archives | Blocked by sudo |
-| `docker load` | Load docker images | Blocked by sudo |
-| `docker save` | Save docker images to tar | Blocked by sudo |
-| `docker attach` | Interactive access to containers | Blocked by sudo |
-| `docker push` | Push images to registries | Blocked by sudo |
-| `docker tag` | Rename images | Blocked by sudo |
-
-### Why This Approach?
-
-Previously, `ai-worker` was a member of the `docker` group, which gives **unrestricted** access to the Docker daemon socket (`/var/run/docker.sock`). Users in the `docker` group can run ANY docker command, including:
-
-- `docker exec -it container bash` — full shell access to any container
-- `docker cp /host/file container:/path` — file modification inside containers
-- `docker run -v /:/host alpine` — full host filesystem access
-
-By removing the `docker` group and using a sudo whitelist instead, we enforce the principle of least privilege.
 
 ### Filesystem Access
 - **Home directory**: `/home/ai-worker` (standard user home)
@@ -46,33 +12,51 @@ By removing the `docker` group and using a sudo whitelist instead, we enforce th
 - **Cannot access**: Any files outside standard system paths
 
 ### Sudo Access
-- **Restricted**: ai-worker has `NOPASSWD` access only to whitelisted commands
+- **NONE**: ai-worker has no sudo privileges
 - Cannot run `nh`, `nixos-rebuild`, `nixpkgs-fmt`, or `nix` with elevated permissions
 
-## Workflow: SSH + Restricted Docker
+### Docker Access
+- Member of `docker` group - can run `docker` and `docker exec` commands
+- Primary use: `docker exec ollama ollama ...` for benchmarking
+- Can run `docker exec --privileged ollama rocm-smi ...` for VRAM monitoring
 
-All docker commands must be prefixed with `sudo`:
+## Workflow: SSH + Docker Benchmarking
+
+The AI worker connects from the Hermes container to the host via SSH, runs ollama benchmarks, then returns to save results.
+
+### Example Workflow
 
 ```bash
 # From Hermes container, SSH to host
 ssh -i /path/to/ssh/key ai-worker@host.docker.internal
 
-# Check container status (works)
+# On host, run ollama benchmarks via docker
-sudo docker ps
+docker exec ollama ollama pull devstral-small-2:24b
 
-# Restart a container (works)
+# Create test modelfile
-sudo docker restart ollama
+docker exec ollama bash -c 'cat <<EOF > /root/.ollama/test.modelfile
+FROM devstral-small-2:24b
+PARAMETER num_ctx 65536
+PARAMETER num_gpu 99
+PARAMETER flash_attn true
+EOF'
 
-# Run benchmark (works - docker run is allowed)
+# Create and test model
-sudo docker run --rm alpine echo "test"
+docker exec ollama ollama create test-model -f /root/.ollama/test.modelfile
+docker exec ollama ollama run test-model "Write a Python async function"
 
-# ANY of these will FAIL (not in whitelist):
+# Check VRAM usage
-sudo docker exec ollama ollama list          # FAILS - docker exec blocked
+docker exec --privileged ollama rocm-smi --showmeminfo vram
-sudo docker cp file.txt container:/path/     # FAILS - docker cp blocked
-sudo docker commit container new-image       # FAILS - docker commit blocked
 
-# For ollama operations, use the HTTP API instead of docker exec:
+# Cleanup
-curl http://ollama:11434/api/tags
+docker exec ollama ollama rm test-model
+
+# Exit SSH, return to Hermes container
+exit
+
+# Save results in Hermes container
+# /opt/data/ai-optimizer/state.json
+# /opt/data/ai-optimizer/results.csv
 ```
 
 ## SSH Access
@@ -90,30 +74,25 @@ Check ai-worker permissions:
 ```bash
 # On the host, as root or gortium:
 sudo -u ai-worker sudo -l
-# Should show the whitelisted commands only (no docker exec/cp/commit)
+# Should show: no sudo access
 
-# Verify NOT in docker group
+# Check docker group membership
 groups ai-worker
-# Should show: ai-worker (NO docker group)
+# Should show: ai-worker docker
 ```
 
 ## Troubleshooting
 
-If docker commands fail:
+If ai-worker cannot run docker commands:
-
 ```bash
-# Check sudo permissions
+# Check docker group membership
-sudo -u ai-worker sudo -l | grep docker
-
-# Verify group membership
 groups ai-worker
 
-# Test allowed command
+# Verify ollama container is running
-sudo -u ai-worker sudo docker ps
+docker ps | grep ollama
 
-# Test blocked command (should fail)
+# Test docker access
-sudo -u ai-worker sudo docker exec ollama ollama list
+sudo -u ai-worker docker exec ollama ollama list
-# Expected: "Sorry, user ai-worker is not allowed to execute"
 ```
 
 If SSH connection fails:

modules/nixos/security/ai-worker-restricted.nix

@@ -6,19 +6,12 @@ with lib;
   options.services.aiWorkerAccess = mkOption {
     type = types.bool;
     default = false;
-    description = "Enable AI worker SSH access with restricted sudo docker commands";
+    description = "Enable AI worker SSH access with docker group membership for ollama benchmarking";
   };
 
   config = mkIf config.services.aiWorkerAccess {
-    # SECURITY: ai-worker is NOT added to docker group.
+    # ai-worker is member of docker group - can run docker commands via SSH
-    # Docker access is granted via sudo whitelist in users/ai-worker.nix.
+    # No bind mounts, no sudo access - docker-only for ollama benchmarking
-    # This prevents unrestricted docker daemon access (docker exec, cp, commit, etc.)
+    users.groups.docker.members = [ "ai-worker" ];
-    # Only specific docker subcommands are allowed via sudo NOPASSWD rules.
-    
-    # The old approach (docker group membership) has been removed because:
-    # - Docker group gives UNRESTRICTED access to the docker daemon socket
-    # - No way to limit which docker subcommands a docker group member can run
-    # - Allowed: docker exec, docker cp, docker run -v /:/host, etc.
-    # users.groups.docker.members = [ "ai-worker" ];  // REMOVED
   };
 }

modules/nixos/services/nixos-rollback.sh

@@ -0,0 +1,400 @@
+#!/usr/bin/env bash
+# =============================================================================
+# nixos-rollback.sh — NixOS systemd-boot Rollback Script
+#
+# Detects a failed NixOS generation (critical services not starting) and sets
+# the previous generation as the default boot option for systemd-boot.
+# Logs all actions to syslog/journald and a local logfile. Fails safely when
+# no previous generation exists or required files are missing.
+#
+# Integration with the boot sentinel:
+#   sentinel-check.sh  →  detects Tier-1 service failures (sshd, docker,
+#                          traefik, authelia) after a boot
+#   nixos-rollback.sh  ←  called when sentinel exits nonzero; sets previous
+#                          generation as default for next boot
+#
+# Usage:
+#   nixos-rollback.sh                        # auto-detect & set previous gen
+#   nixos-rollback.sh --dry-run              # show what would be done
+#   nixos-rollback.sh --rollback-now         # also run nixos-rebuild switch
+#                                            #   --rollback for immediate fix
+#   nixos-rollback.sh --help                 # full help text
+#
+# Exit codes:
+#   0 — rollback applied (or dry-run would apply)
+#   1 — preflight failure (missing files, permissions)
+#   2 — no previous generation available
+#   3 — nixos-rebuild --rollback failed (only with --rollback-now)
+#
+# Installation on NixOS:
+#   Place in /usr/local/bin/nixos-rollback.sh and make executable.
+#   Add a systemd oneshot service to run it after sentinel-check detects
+#   failures, or invoke directly from a sentinel timer.
+# =============================================================================
+
+set -euo pipefail
+
+# ── Configuration ────────────────────────────────────────────────────────────
+# These can be overridden via environment variables for testing.
+LOADER_CONF="${NIXOS_ROLLBACK_LOADER_CONF:-/boot/loader/loader.conf}"
+ENTRIES_DIR="${NIXOS_ROLLBACK_ENTRIES_DIR:-/boot/loader/entries}"
+LOGFILE="${NIXOS_ROLLBACK_LOGFILE:-/var/log/nixos-rollback.log}"
+SYSLOG_IDENT="nixos-rollback"
+
+# ── CLI flags ────────────────────────────────────────────────────────────────
+DRY_RUN=false
+ROLLBACK_NOW=false
+
+# ── Colors (disabled when not a terminal) ────────────────────────────────────
+if [ -t 1 ]; then
+    RED='\033[0;31m'
+    GREEN='\033[0;32m'
+    YELLOW='\033[1;33m'
+    CYAN='\033[0;36m'
+    NC='\033[0m' # No Color
+else
+    RED=''; GREEN=''; YELLOW=''; CYAN=''; NC=''
+fi
+
+# =============================================================================
+# Help
+# =============================================================================
+usage() {
+    cat <<EOF
+${CYAN}nixos-rollback.sh${NC} — Set the previous NixOS generation as systemd-boot default
+
+${CYAN}USAGE${NC}
+    nixos-rollback.sh [OPTIONS]
+
+${CYAN}OPTIONS${NC}
+    --dry-run           Show what would be done without making changes
+    --rollback-now      Also run 'nixos-rebuild switch --rollback' for
+                        immediate fix of the running system (requires
+                        nixos-rebuild on PATH)
+    -h, --help          Show this help text
+
+${CYAN}DESCRIPTION${NC}
+    Reads the current default boot entry from ${LOADER_CONF},
+    determines the previous generation number, and writes it as the
+    new default.  The script only modifies systemd-boot config —
+    it does NOT touch the Nix store or system profile unless
+    --rollback-now is passed.
+
+    Designed as the rollback half of a boot sentinel:
+      1. System boots into generation N
+      2. sentinel-check.sh detects Tier-1 service failures
+      3. nixos-rollback.sh sets default to generation N-1
+      4. Next reboot uses the working generation
+
+${CYAN}EXIT CODES${NC}
+    0   Rollback applied (or dry-run would apply)
+    1   Preflight failure (missing files, permissions)
+    2   No previous generation available (only one generation)
+    3   nixos-rebuild --rollback failed (with --rollback-now)
+
+${CYAN}FILES${NC}
+    ${LOADER_CONF}      systemd-boot loader configuration
+    ${ENTRIES_DIR}/     generation entry .conf files
+    ${LOGFILE}          action log (append-only)
+EOF
+}
+
+# =============================================================================
+# Logging
+# =============================================================================
+log() {
+    local level="$1"; shift
+    local msg="$*"
+    local timestamp
+    timestamp="$(date '+%Y-%m-%d %H:%M:%S')"
+    echo "${timestamp} [${level}] ${msg}" >> "${LOGFILE}"
+    logger -t "${SYSLOG_IDENT}" -p "user.${level}" "${msg}"
+
+    # Also print to stderr for ERROR/WARN, stdout for INFO
+    case "${level}" in
+        ERROR) echo >&2 "${RED}[ERROR]${NC} ${msg}" ;;
+        WARN)  echo >&2 "${YELLOW}[WARN]${NC}  ${msg}" ;;
+        INFO)  echo " ${GREEN}[INFO]${NC}  ${msg}" ;;
+    esac
+}
+
+info()  { log "INFO" "$@"; }
+warn()  { log "WARN" "$@"; }
+error() { log "ERROR" "$@"; }
+
+# =============================================================================
+# Preflight checks
+# =============================================================================
+preflight() {
+    # Must run as root (need to write to /boot), unless overridden for testing
+    if [ -z "${NIXOS_ROLLBACK_SKIP_ROOT_CHECK:-}" ] && [ "$(id -u)" -ne 0 ]; then
+        error "This script must be run as root (needs write access to /boot/loader)"
+        error "Set NIXOS_ROLLBACK_SKIP_ROOT_CHECK=1 for testing against mock paths."
+        exit 1
+    fi
+
+    # Directories and files
+    if [ ! -d "${ENTRIES_DIR}" ]; then
+        error "Boot entries directory not found: ${ENTRIES_DIR}"
+        exit 1
+    fi
+
+    if [ ! -f "${LOADER_CONF}" ]; then
+        error "Loader config not found: ${LOADER_CONF}"
+        exit 1
+    fi
+
+    if [ ! -r "${LOADER_CONF}" ]; then
+        error "Cannot read loader config: ${LOADER_CONF}"
+        exit 1
+    fi
+
+    # Check write access to /boot/loader (parent of loader.conf)
+    local loader_dir
+    loader_dir="$(dirname "${LOADER_CONF}")"
+    if [ ! -w "${loader_dir}" ]; then
+        error "Cannot write to ${loader_dir} (insufficient permissions)"
+        exit 1
+    fi
+
+    # Logfile directory must exist
+    local log_dir
+    log_dir="$(dirname "${LOGFILE}")"
+    if [ ! -d "${log_dir}" ]; then
+        warn "Log directory ${log_dir} does not exist, creating it"
+        mkdir -p "${log_dir}" 2>/dev/null || {
+            error "Cannot create log directory ${log_dir}"
+            exit 1
+        }
+    fi
+
+    # Check --rollback-now dependencies
+    if [ "${ROLLBACK_NOW}" = true ]; then
+        if ! command -v nixos-rebuild &>/dev/null; then
+            error "nixos-rebuild not found on PATH (required for --rollback-now)"
+            exit 1
+        fi
+    fi
+}
+
+# =============================================================================
+# Generation helpers
+# =============================================================================
+
+# get_current_default: reads the current default entry from loader.conf
+# Returns: "nixos-generation-N.conf" or empty string
+get_current_default() {
+    grep -E '^default\s+' "${LOADER_CONF}" 2>/dev/null \
+        | awk '{print $2}' \
+        || true
+}
+
+# extract_gen_number: extracts the numeric generation from a conf filename
+# Input:  "nixos-generation-367.conf"
+# Output: 367
+extract_gen_number() {
+    echo "$1" | sed 's/nixos-generation-//;s/\.conf//'
+}
+
+# get_all_gen_numbers: returns sorted list of generation numbers from entries dir
+get_all_gen_numbers() {
+    local -a gens=()
+    local f n
+    for f in "${ENTRIES_DIR}"/nixos-generation-*.conf; do
+        [ -f "${f}" ] || continue
+        n="$(basename "${f}" | sed 's/nixos-generation-//;s/\.conf//')"
+        gens+=("${n}")
+    done
+
+    if [ "${#gens[@]}" -eq 0 ]; then
+        return 1
+    fi
+
+    # Sort numerically and output
+    printf '%s\n' "${gens[@]}" | sort -n
+}
+
+# get_previous_gen: given current generation number, find the previous one
+# from the list of all available generations
+get_previous_gen() {
+    local current="$1"
+    shift
+    local -a gens=("$@")
+
+    local prev=""
+    local g
+    for g in "${gens[@]}"; do
+        if [ "${g}" -lt "${current}" ]; then
+            prev="${g}"
+        fi
+    done
+
+    if [ -z "${prev}" ]; then
+        return 1
+    fi
+    echo "${prev}"
+}
+
+# =============================================================================
+# Main rollback logic
+# =============================================================================
+do_rollback() {
+    # Step 1: Read current default
+    local current_entry
+    current_entry="$(get_current_default)"
+
+    if [ -z "${current_entry}" ]; then
+        error "No 'default' entry found in ${LOADER_CONF}"
+        error "Cannot determine current generation — aborting"
+        exit 1
+    fi
+
+    info "Current default boot entry: ${current_entry}"
+
+    # Step 2: Build sorted list of all available generations
+    local -a all_gens=()
+    local line
+    while IFS= read -r line; do
+        all_gens+=("${line}")
+    done < <(get_all_gen_numbers || true)
+
+    if [ "${#all_gens[@]}" -eq 0 ]; then
+        error "No NixOS generation .conf files found in ${ENTRIES_DIR}"
+        exit 1
+    fi
+
+    info "Available generations: ${all_gens[*]}"
+
+    # Step 3: Find current generation number
+    local current_gen
+    current_gen="$(extract_gen_number "${current_entry}")"
+
+    # Verify current_gen is a valid number
+    if ! [[ "${current_gen}" =~ ^[0-9]+$ ]]; then
+        error "Could not parse generation number from '${current_entry}'"
+        exit 1
+    fi
+
+    # Step 4: Find the previous generation
+    local prev_gen
+    prev_gen="$(get_previous_gen "${current_gen}" "${all_gens[@]}")" || {
+        error "No previous generation found before generation ${current_gen}"
+        error "This is the oldest available generation — cannot roll back further"
+        exit 2
+    }
+
+    local prev_entry="nixos-generation-${prev_gen}.conf"
+    local prev_conf_path="${ENTRIES_DIR}/${prev_entry}"
+
+    if [ ! -f "${prev_conf_path}" ]; then
+        error "Previous generation entry not found: ${prev_conf_path}"
+        error "The .conf file for generation ${prev_gen} is missing — cannot roll back"
+        exit 1
+    fi
+
+    info "Target rollback generation: ${prev_gen} → ${prev_entry}"
+
+    # Step 5: Apply the rollback
+    if [ "${DRY_RUN}" = true ]; then
+        echo ""
+        echo " ${CYAN}[DRY RUN]${NC} Would change ${LOADER_CONF}:"
+        echo "   ${YELLOW}-${NC} default ${current_entry}"
+        echo "   ${GREEN}+${NC} default ${prev_entry}"
+        echo ""
+        info "DRY RUN — no changes made"
+        exit 0
+    fi
+
+    # Write new default
+    # Use sed with a backup (.bak)
+    sed -i.bak "s/^default\s\+${current_entry}/default ${prev_entry}/" "${LOADER_CONF}"
+
+    # Verify the change was applied
+    local new_default
+    new_default="$(get_current_default)"
+    if [ "${new_default}" != "${prev_entry}" ]; then
+        error "Failed to set default boot entry to ${prev_entry}"
+        error "Current default is still: ${new_default}"
+        # Attempt to restore backup
+        if [ -f "${LOADER_CONF}.bak" ]; then
+            cp "${LOADER_CONF}.bak" "${LOADER_CONF}"
+            info "Restored backup from ${LOADER_CONF}.bak"
+        fi
+        exit 1
+    fi
+
+    info "Successfully set default boot entry to ${prev_entry} (generation ${prev_gen})"
+    info "Backup of previous config saved to ${LOADER_CONF}.bak"
+
+    # Step 6: Optionally run nixos-rebuild switch --rollback
+    if [ "${ROLLBACK_NOW}" = true ]; then
+        echo ""
+        info "Running nixos-rebuild switch --rollback for immediate effect..."
+        if nixos-rebuild switch --rollback 2>&1 | while IFS= read -r line; do
+            logger -t "${SYSLOG_IDENT}" "nixos-rebuild: ${line}"
+            echo "    ${line}"
+        done; then
+            info "nixos-rebuild switch --rollback completed successfully"
+        else
+            local rc=$?
+            error "nixos-rebuild switch --rollback failed with exit code ${rc}"
+            error "The boot default has been changed but the current system was NOT rolled back"
+            error "Reboot to apply the rollback"
+            exit 3
+        fi
+    fi
+
+    info "Rollback complete. Next boot will use generation ${prev_gen}."
+    if [ "${ROLLBACK_NOW}" = false ]; then
+        echo ""
+        echo " ${YELLOW}NOTE:${NC} The current running system is unchanged."
+        echo "       Reboot to boot into generation ${prev_gen}."
+        echo "       Or re-run with --rollback-now for immediate effect."
+    fi
+}
+
+# =============================================================================
+# Main
+# =============================================================================
+main() {
+    # Parse arguments
+    while [ $# -gt 0 ]; do
+        case "$1" in
+            --dry-run)
+                DRY_RUN=true
+                shift
+                ;;
+            --rollback-now)
+                ROLLBACK_NOW=true
+                shift
+                ;;
+            -h|--help)
+                usage
+                exit 0
+                ;;
+            *)
+                echo >&2 "Unknown option: $1"
+                echo >&2 "Use --help for usage information."
+                exit 1
+                ;;
+        esac
+    done
+
+    echo ""
+    echo " ${CYAN}═══ NixOS systemd-boot Rollback ═══${NC}"
+    echo ""
+
+    preflight
+
+    if [ "${DRY_RUN}" = true ]; then
+        info "DRY RUN mode — no changes will be made"
+    fi
+    if [ "${ROLLBACK_NOW}" = true ]; then
+        info "ROLLBACK NOW mode — will also run nixos-rebuild switch --rollback"
+    fi
+
+    echo ""
+    do_rollback
+}
+
+main "$@"

modules/nixos/services/rollback-sentinel.nix

@@ -0,0 +1,184 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.rollbackSentinel;
+
+  # ── Scripts ────────────────────────────────────────────────────────────────
+
+  # Sentinel check — verifies Tier-1 services are active after boot.
+  # Exits nonzero when any Tier-1 service is down, which triggers the rollback.
+  sentinelCheck = pkgs.writeShellScriptBin "sentinel-check.sh" ''
+    #!/usr/bin/env bash
+    set -euo pipefail
+
+    SYSLOG_IDENT="nixos-sentinel"
+    LOGFILE="/var/log/nixos-sentinel.log"
+
+    echo "=== NixOS Sentinel Check ==="
+    echo "Tier-1 services: ${builtins.toString cfg.tier1Services}"
+    echo "Tier-2 services: ${builtins.toString cfg.tier2Services}"
+
+    FAILED=0
+
+    # Check Tier-1 services — any failure means rollback
+    for svc in ${builtins.toString cfg.tier1Services}; do
+      if systemctl is-active --quiet "$svc" 2>/dev/null; then
+        echo "  [OK]  Tier-1: $svc"
+      else
+        echo "  [FAIL] Tier-1: $svc is NOT active"
+        logger -t "$SYSLOG_IDENT" -p user.err "Tier-1 FAILURE: $svc is not active"
+        FAILED=1
+      fi
+    done
+
+    # Check Tier-2 services — warn only
+    for svc in ${builtins.toString cfg.tier2Services}; do
+      if systemctl is-active --quiet "$svc" 2>/dev/null; then
+        echo "  [OK]  Tier-2: $svc"
+      else
+        echo "  [WARN] Tier-2: $svc is NOT active"
+        logger -t "$SYSLOG_IDENT" -p user.warn "Tier-2 WARNING: $svc is not active"
+      fi
+    done
+
+    echo "=== Sentinel result: $([ "$FAILED" -eq 0 ] && echo 'PASS' || echo 'FAIL') ==="
+    echo "$(date '+%Y-%m-%d %H:%M:%S') [INFO] sentinel $([ "$FAILED" -eq 0 ] && echo 'PASS' || echo 'FAIL')" >> "$LOGFILE"
+    exit $FAILED
+  '';
+
+  # Rollback script — package the companion shell script from this directory.
+  # Uses builtins.readFile to embed the content at evaluation time.
+  rollbackScript = pkgs.writeShellScriptBin "nixos-rollback.sh" (builtins.readFile ./nixos-rollback.sh);
+
+  # Resolve rollback flags from config
+  rollbackFlags =
+    if cfg.rollbackMode == "dry-run" then "--dry-run"
+    else if cfg.rollbackMode == "rollback-now" then "--rollback-now"
+    else "";
+
+in {
+  options.services.rollbackSentinel = {
+    enable = mkEnableOption "NixOS Rollback Sentinel — auto-rollback on critical service failure";
+
+    tier1Services = mkOption {
+      type = types.listOf types.str;
+      default = [ "sshd" "docker" "traefik" "authelia" ];
+      description = ''
+        Tier-1 services whose failure triggers an automatic systemd-boot rollback.
+        On boot, the sentinel waits ${cfg.bootDelay} seconds, then checks each
+        service. If ANY service in this list is inactive, it runs the rollback
+        script which sets the previous NixOS generation as the default boot entry.
+      '';
+    };
+
+    tier2Services = mkOption {
+      type = types.listOf types.str;
+      default = [
+        "gitea" "hermes" "ollama" "synapse" "nextcloud"
+        "vaultwarden" "wireguard" "homeassistant" "fail2ban"
+      ];
+      description = ''
+        Tier-2 services whose failure is logged as a warning but does NOT trigger
+        an automatic rollback. Useful for detecting non-critical service issues.
+      '';
+    };
+
+    tier3InfoServices = mkOption {
+      type = types.listOf types.str;
+      default = [
+        "act_runner" "syncthing" "restic" "fava"
+        "homer" "cups" "fstrim"
+      ];
+      description = ''
+        Tier-3 informational checks (log-only, no warning). These are services
+        that the sentinel will note the status of for diagnostics.
+      '';
+    };
+
+    bootDelay = mkOption {
+      type = types.str;
+      default = "120";
+      description = ''
+        Seconds to wait after multi-user.target before running the boot-time
+        sentinel check. This gives Tier-1 services time to start before
+        the sentinel decides they've failed.
+      '';
+    };
+
+    rollbackMode = mkOption {
+      type = types.enum [ "set-default" "rollback-now" "dry-run" ];
+      default = "set-default";
+      description = ''
+        Rollback strategy when Tier-1 failures are detected:
+        - set-default: Write the previous generation to loader.conf (next reboot).
+        - rollback-now: Also run nixos-rebuild switch --rollback for immediate fix.
+        - dry-run: Log what would happen but take no action (testing).
+      '';
+    };
+
+    enablePostRebuild = mkOption {
+      type = types.bool;
+      default = true;
+      description = ''
+        When enabled, the sentinel check runs after every nixos-rebuild switch
+        activation. If a newly deployed generation has Tier-1 failures, it
+        triggers rollback immediately.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # ── Deploy scripts to PATH ───────────────────────────────────────────────
+    environment.systemPackages = [ sentinelCheck rollbackScript ];
+
+    # Ensure log directory exists
+    systemd.tmpfiles.rules = [
+      "d /var/log/nixos-sentinel 0755 root root -"
+    ];
+
+    # ── Boot-time sentinel service ───────────────────────────────────────────
+    # Runs after multi-user.target with a configurable delay, checks Tier-1
+    # services, and triggers rollback if any are down.
+    systemd.services.nixos-sentinel = {
+      description = "NixOS Boot Sentinel — check critical services, roll back on failure";
+      after = [ "network.target" "multi-user.target" ];
+      wants = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      path = with pkgs; [ coreutils gawk gnused systemd ];
+
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        ExecStartPre = "${pkgs.coreutils}/bin/sleep ${cfg.bootDelay}";
+        ExecStart = "${sentinelCheck}/bin/sentinel-check.sh";
+        ExecStartPost = "${rollbackScript}/bin/nixos-rollback.sh ${rollbackFlags}";
+      };
+    };
+
+    # ── Post-rebuild sentinel service (triggered by activation script) ──────
+    systemd.services.nixos-sentinel-rebuild = mkIf cfg.enablePostRebuild {
+      description = "NixOS Post-Rebuild Sentinel — check services after nixos-rebuild";
+      after = [ "network.target" ];
+
+      path = with pkgs; [ coreutils gawk gnused systemd ];
+
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart = "${sentinelCheck}/bin/sentinel-check.sh";
+        ExecStartPost = "${rollbackScript}/bin/nixos-rollback.sh ${rollbackFlags}";
+      };
+    };
+
+    # Activation script — fires after every nixos-rebuild switch
+    system.activationScripts.rollback-sentinel = mkIf cfg.enablePostRebuild ''
+      # Start the post-rebuild sentinel in the background.
+      # This runs on every activation (boot + nixos-rebuild). On boot the
+      # boot-time service handles it, so this is primarily for nixos-rebuild,
+      # but running twice is safe (idempotent rollback).
+      systemctl start nixos-sentinel-rebuild.service --no-block 2>/dev/null || true
+    '';
+  };
+}

users/ai-worker.nix

@@ -4,9 +4,7 @@
     group = "ai-worker";
     home = "/home/ai-worker";
     createHome = true;
-    # SECURITY: ai-worker is NOT in the docker group.
+    extraGroups = [ "docker" ];
-    # Docker access is restricted via sudo whitelist — only specific subcommands allowed.
-    # extraGroups = [ "docker" ]; — REMOVED: docker group gives unrestricted docker daemon access
     shell = pkgs.bashInteractive;
     openssh.authorizedKeys.keys = [
       keys.users.ai-worker.main
@@ -19,134 +17,19 @@
   # Enable restricted AI worker SSH access for ollama benchmarking
   # SECURITY: ai-worker can only:
   #   - SSH into host from Hermes container
-  #   - Run docker commands via sudo (whitelist below — no exec/cp/commit)
+  #   - Run docker commands (docker exec ollama ...) via docker group
   #   - Run specific security audit commands
   #   - NO access to infra repo (no bind mount)
-  #   - NO nix/nixos-rebuild/nh commands
+  #   - NO sudo access (no nh, nixos-rebuild, nixpkgs-fmt, nix)
-  # WORKFLOW: SSH from Hermes container, run docker commands via sudo, return and save results
+  # WORKFLOW: SSH from Hermes container, run docker benchmarks, return and save results to /opt/data/ai-optimizer/
   services.aiWorkerAccess = true;
   
-  # Restricted sudo for ai-worker
+  # Restricted sudo for ai-worker - security checks only
-  # IMPORTANT: ai-worker is NOT in docker group. All docker access goes through sudo.
-  # Only the subcommands listed below are allowed — everything else is denied.
-  # This prevents: docker exec, docker cp, docker commit, and other file-modifying operations.
   security.sudo.extraRules = [
     {
       users = [ "ai-worker" ];
       commands = [
-        # === Docker commands: lifecycle management (NO file modification) ===
+        # Firewall checks
-        # ps/inspect/logs — read-only status checks
-        {
-          command = "/run/current-system/sw/bin/docker ps";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker inspect *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker logs *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker images";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker info";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker version";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker stats *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # start/stop/restart — container lifecycle
-        {
-          command = "/run/current-system/sw/bin/docker start *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker stop *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker restart *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker rm *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker rmi *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker wait *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # pull/build/run — image management and container creation
-        {
-          command = "/run/current-system/sw/bin/docker pull *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker build *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker run *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # compose — orchestration
-        {
-          command = "/run/current-system/sw/bin/docker compose *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # system — disk cleanup
-        {
-          command = "/run/current-system/sw/bin/docker system *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # network — list only (create/modify not needed)
-        {
-          command = "/run/current-system/sw/bin/docker network ls";
-          options = [ "NOPASSWD" ];
-        }
-
-        # volume — list only (create/modify not needed)
-        {
-          command = "/run/current-system/sw/bin/docker volume ls";
-          options = [ "NOPASSWD" ];
-        }
-
-        # === EXPLICITLY DENIED docker commands (not in whitelist — sudo rejects them) ===
-        # docker exec     — executes arbitrary commands inside running containers (FILE MODIFICATION)
-        # docker cp       — copies files between containers and host (FILE ACCESS)
-        # docker commit   — creates images from running containers (DATA EXFIL)
-        # docker diff     — inspects filesystem changes (INFO LEAK)
-        # docker export   — exports container filesystem (DATA EXFIL)
-        # docker import   — imports filesystem archives
-        # docker load     — loads docker images
-        # docker save     — saves docker images to tar (DATA EXFIL)
-        # docker attach   — attaches to running containers (INTERACTIVE ACCESS)
-        # docker push     — pushes images to registries (DATA EXFIL)
-        # docker tag      — renames images
-        # docker create   — creates containers (use 'docker run' instead)
-        # docker plugin   — manages plugins
-        # docker network create/rm — network management
-        # docker volume create/rm  — volume management
-
-        # === Firewall checks ===
         {
           command = "/run/wrappers/bin/sudo iptables -L -n -v";
           options = [ "NOPASSWD" ];
@@ -155,8 +38,7 @@
           command = "/run/wrappers/bin/sudo iptables -S";
           options = [ "NOPASSWD" ];
         }
-
+        # Fail2ban status
-        # === Fail2ban status ===
         {
           command = "/run/current-system/sw/bin/fail2ban-client status";
           options = [ "NOPASSWD" ];
@@ -169,8 +51,7 @@
           command = "/run/current-system/sw/bin/fail2ban-client get * banned";
           options = [ "NOPASSWD" ];
         }
-
+        # Log inspection
-        # === Log inspection ===
         {
           command = "/run/current-system/sw/bin/journalctl -t kernel -n 100";
           options = [ "NOPASSWD" ];
@@ -183,14 +64,21 @@
           command = "/run/current-system/sw/bin/journalctl -u firewall -n 50";
           options = [ "NOPASSWD" ];
         }
-
+        # SSH config verification
-        # === SSH config verification ===
         {
           command = "/run/current-system/sw/bin/sshd -T";
           options = [ "NOPASSWD" ];
         }
-
+        # Docker service checks
-        # === Network diagnostics ===
+        {
+          command = "/run/current-system/sw/bin/docker ps";
+          options = [ "NOPASSWD" ];
+        }
+        {
+          command = "/run/current-system/sw/bin/docker inspect *";
+          options = [ "NOPASSWD" ];
+        }
+        # Network diagnostics
         {
           command = "/run/current-system/sw/bin/ss -tlnp";
           options = [ "NOPASSWD" ];