FakeNotify

Transparent inotify injection for NFS filesystems

FakeNotify solves the fundamental problem that NFS mounts don't emit inotify events, breaking applications like Jellyfin, Plex, Sonarr, Radarr, and qBittorrent that rely on filesystem change notifications.

How It Works

┌─────────────────────────────────────────────────┐
│ Application (Jellyfin, Sonarr, etc.)            │
│                                                  │
│ inotify_init() ──→ [HOOK] ──→ returns pipe fd   │
│ inotify_add_watch() ──→ [HOOK] ──→ returns wd   │
│ read(fd) ←── receives inotify_event structs ────┤
└─────────────────────────────────────────────────┘
                    ↑
          LD_PRELOAD=libfakenotify.so
                    ↑
              Unix Socket IPC
                    ↓
┌─────────────────────────────────────────────────┐
│ fakenotifyd (daemon)                            │
│                                                  │
│ • Polls NFS mounts for changes                  │
│ • Tracks watch descriptors ↔ paths              │
│ • Writes synthetic inotify_event to pipes       │
│ • CLI for runtime configuration                 │
└─────────────────────────────────────────────────┘

Two components:

1. libfakenotify.so - LD_PRELOAD library that intercepts inotify_init, inotify_add_watch, inotify_rm_watch, returns pipe fds instead, and connects to the daemon
2. fakenotifyd - Background daemon that polls NFS paths, detects changes, and writes synthetic inotify_event structs to connected applications

Features

• Transparent - No application modifications needed, just LD_PRELOAD
• Docker-friendly - Works with containerized apps via volume-mounted socket
• Configurable polling - Adjust intervals per-path based on your needs
• Runtime CLI - Add/remove watched paths without restart

Installation

One-Liner (Recommended)

curl -sSL https://raw.githubusercontent.com/zachhandley/FakeNotify/main/install-release.sh | sudo bash

Then configure and start:

sudo nano /etc/fakenotify/config.toml  # Add your NFS paths
sudo systemctl enable --now fakenotify

From Source

git clone https://github.com/zachhandley/FakeNotify.git
cd FakeNotify
cargo build --release
sudo ./install.sh

Usage

Start the daemon

# Start with default config
fakenotifyd start

# Or specify config file
fakenotifyd start --config /etc/fakenotify/config.toml

Configure watched paths

# Add an NFS path to monitor
fakenotifyd add /mnt/media --poll-interval 5s

# Remove a path
fakenotifyd remove /mnt/media

# List watched paths
fakenotifyd list

# Check status
fakenotifyd status

Run applications with injection

# Single application
LD_PRELOAD=/usr/lib/libfakenotify.so jellyfin

# Docker container
docker run -e LD_PRELOAD=/fakenotify/libfakenotify.so \
           -v /usr/lib/libfakenotify.so:/fakenotify/libfakenotify.so:ro \
           -v /run/fakenotify.sock:/run/fakenotify.sock \
           jellyfin/jellyfin

Docker Integration

The daemon runs on the host, containers just need the library and socket mounted.

# docker-compose.yml
services:
  jellyfin:
    image: jellyfin/jellyfin
    environment:
      - LD_PRELOAD=/usr/local/lib/libfakenotify_preload.so
    volumes:
      # Mount the socket directory and library
      - /run/fakenotify:/run/fakenotify:ro
      - /usr/local/lib/libfakenotify_preload.so:/usr/local/lib/libfakenotify_preload.so:ro
      # Your NFS media
      - /mnt/media:/media

Two mounts: the socket directory and the library file.

LinuxServer.io Containers (DockerMod)

For LSIO containers (Sonarr, Radarr, etc.), use the DockerMod - zero config needed:

services:
  sonarr:
    image: linuxserver/sonarr
    environment:
      - DOCKER_MODS=ghcr.io/zachhandley/fakenotify-mod:latest
    volumes:
      - /run/fakenotify:/run/fakenotify:ro
      - /usr/local/lib/libfakenotify_preload.so:/usr/local/lib/libfakenotify_preload.so:ro
      - /mnt/media:/media

The mod automatically configures LD_PRELOAD.

Configuration

/etc/fakenotify/config.toml:

[daemon]
socket = "/run/fakenotify.sock"
log_level = "info"

[[watch]]
path = "/mnt/media"
poll_interval = "5s"
recursive = true

[[watch]]
path = "/mnt/downloads"
poll_interval = "2s"
recursive = true

How NFS + inotify Breaks

Linux's inotify monitors filesystem changes at the kernel VFS layer. When files change on an NFS server (or from another NFS client), the local kernel never sees the operation - it happens remotely. Therefore, inotify watches on NFS mounts are silent.

This affects:

• Jellyfin/Plex/Emby - Library not updating when new media added
• Sonarr/Radarr - Downloads not detected (when using folder watching)
• qBittorrent - Watched folders not triggering
• Any app using inotify, fswatch, watchdog, etc.

Technical Details

LD_PRELOAD Library

Uses the redhook crate to intercept:

• inotify_init() / inotify_init1() - Returns a pipe fd instead
• inotify_add_watch() - Registers path with daemon, returns synthetic wd
• inotify_rm_watch() - Unregisters path with daemon

The pipe fd is indistinguishable from a real inotify fd to the application - it works with poll(), epoll(), select(), and blocking read().

Daemon Polling

Uses the notify crate with PollWatcher backend:

• Periodic stat() calls to detect mtime/ctime changes
• Directory listing comparison for create/delete detection
• Debouncing via notify-debouncer-full to coalesce rapid changes

Event Format

Writes standard inotify_event structs to pipes:

struct inotify_event {
    int      wd;       // Watch descriptor
    uint32_t mask;     // Event mask (IN_CREATE, IN_MODIFY, etc.)
    uint32_t cookie;   // Cookie for rename pairing
    uint32_t len;      // Length of name field
    char     name[];   // Filename (variable length)
};

Limitations

• Only affects dynamically linked binaries - Static binaries bypass LD_PRELOAD
• Polling latency - Changes detected on poll interval, not instantly
• NFS attribute caching - May need actimeo=0 mount option for immediate visibility
• No rename cookie pairing - IN_MOVED_FROM/IN_MOVED_TO won't have matching cookies across polls

Requirements

• Linux (uses Linux-specific inotify API)
• Rust 1.75+ (for building)
• NFS mounts accessible to the daemon

License

MIT