# Fenris — NVMe Wear Monitor & Live Dashboard

Created by Bongbetic.

Periodically reads your NVMe drive's SMART health data, logs it over time, and serves a self-contained HTML dashboard estimating SSD lifespan from your actual daily usage trend.

## Requirements

- **Python 3.7+**
- **smartmontools** (`smartctl`) installed
- Root access to read NVMe SMART logs

### Setting up passwordless smartctl

Fenris runs `sudo -n smartctl ...` (no-prompt sudo). Either run with sudo or allow passwordless access:

```bash
sudo visudo
# Add this line (replace youruser with your username):
youruser ALL=(root) NOPASSWD: /usr/sbin/smartctl
```

## Quick Start

### Interactive Menu

```bash
./fenris.sh
```

### CLI

```bash
# Start daemon + dashboard in background
python3 fenris.py start

# Check status and latest wear stats
python3 fenris.py status

# Take one sample now
python3 fenris.py sample

# Stop the daemon
python3 fenris.py stop
```

Dashboard available at: `http://localhost:8420`

## CLI Reference

### fenris.py start

Start monitoring in background (daemon + dashboard).

```bash
python3 fenris.py start [OPTIONS]

Options:
  --device PATH     NVMe device (default: auto-detect, e.g. /dev/nvme0)
  --interval SEC    Seconds between samples (default: 300)
  --port PORT       Dashboard HTTP port (default: 8420)
```

### fenris.py stop

Stop background monitoring and clean up PID file.

### fenris.py status

Show daemon status and latest wear statistics.

### fenris.py sample

Take one sample immediately and print it.

```bash
python3 fenris.py sample [--device /dev/nvme0]
```

### fenris.py run

Run in foreground (used internally by `start`). Not intended for direct use.

## Interactive Menu

Run `./fenris.sh` for a guided interface:

```
 1) Start monitoring (background daemon + dashboard)
 2) Stop monitoring
 3) Status / current wear stats
 4) Take one sample right now
 5) Open dashboard URL
 ---
 h) Help / how this works
 q) Exit
```

## Data Collected

| Field | Description |
|-------|-------------|
| `percentage_used` | SSD's own wear indicator (0-100%) |
| `bytes_written` / `bytes_read` | Total data written/read |
| `available_spare` | Remaining spare capacity (%) |
| `media_errors` | Number of uncorrectable errors |
| `power_on_hours` | Total power-on hours |
| `temperature_c` | Current temperature |
| `critical_warning` | NVMe critical warning flags |

## Dashboard Features

- Real-time wear level + projected life remaining in **hours / days / years** from the actual **rolling-24h write rate** and implied TBW endurance
- Exact **GB written in the last 24 hours** + GB/h and GB/day rate (updates every poll interval)
- Wear-over-time chart + **trailing-24h per-hour write bars**
- Dense layout with sticky header, ETag-cached polling synced to the daemon interval, countdown and live badge, stale/preliminary banners
- API: `GET /api/data`, `/api/hourly`, `/api/summary`, `/api/config`, `/api/status`

## File Structure

```
fenris/
├── fenris.py          # Main Python script
├── fenris.sh          # Interactive menu wrapper
├── README.md
└── data/
    ├── history.jsonl   # Raw sample log (JSONL)
    ├── hourly.jsonl    # Per-hour aggregates (rebuilt from history on restart)
    ├── fenris.pid      # Daemon PID file
    └── fenris.log      # Daemon log output
```

## Troubleshooting

**"smartctl not found"**
```bash
sudo apt install smartmontools    # Debian/Ubuntu
sudo pacman -S smartmontools      # Arch
```

**"needs root" / permission denied**
Set up passwordless sudo (see Requirements) or run with sudo.

**Dashboard shows "stale"**
Daemon not running. Check with `python3 fenris.py status` and restart if needed.