silod

silod is a tiny Rust daemon that monitors the TS‑SILO super‑capacitor backup power supply and orchestrates a graceful shutdown (plus any user‑defined helper scripts) when input power is lost. It is intended for embedded Linux systems that use the tssilo kernel driver (exposed via sysfs).

Features:

• Watches the kernel uevent multicast stream for power‑supply change events (no polling).
• Executes event‑specific hooks in /etc/silod/scripts.d/:
  • power-fail
  • power-restored
  • fully-charged
  • critical
• Applies configuration to the driver on startup (charge_behaviour, capacity thresholds, current limits…).
• Logs to stdout when run interactively, or to syslog (LOG_DAEMON) when run as a background service.
• Re‑execs shutdown -p now automatically once a critical capacity threshold is crossed.

Install

Build on the target platform

Install rust if it is not already present, either through the distribution or rustup

# Fetch and build
git clone https://github.com/embeddedTS/silod.git
cd silod
cargo build --release

# Install the binary (requires root for /usr/sbin)
sudo install -m 0755 target/release/silod /usr/sbin/
sudo mkdir -p /etc/silod/scripts.d/{power-fail,power-restored,fully-charged,critical}

Usage

# As root:
silod
systemctl start silod.service

Default behaviour

Event	Condition	Hook executed
Initial charge	First run after boot	–
Fully charged	Online and capacity == 100 %	fully-charged
Power‑fail	Input lost while current capacity ≥ threshold	power-fail
Power‑restored	Input restored	power-restored
Critical	capacity < critical_pct	critical

Configuration file

/etc/silod/silo.toml

# Mandatory: percent below which the system shuts down
critical_pct = 60

# Optional: enable or inhibit charging (maps to charge_behaviour)
enable_charging = true

# Optional: minimum capacity required before the board may power on again
min_power_on_pct = 80

# Optional: initial charge current (mA) applied after a brown‑out
startup_charge_current_ma = 500

All values are written to /sys/class/power_supply/tssilo/… and logged back for verification.

Scripts

Place any executable files in /etc/silod/scripts.d in one of the directories:

• power-fail
• power-restored
• fully-charged
• critical

Example:

#!/bin/sh
#/etc/silod/scripts.d/critical/01-send-shutdown-message.sh

curl -X POST http://your-server.example.com/log \
     -H "Content-Type: application/json" \
     -d '{"level": "info", "message": "System is shutting down due supercaps draining", "timestamp": "'"$(date -Is)"'"}'

Scripts are executed sequentially in filename order. Failures are logged, but do not abort the chain.

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Running as a systemd service

# /etc/systemd/system/silod.service
[Unit]
Description=TS‑SILO supercap backup monitor
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/sbin/silod
Restart=always
User=root
Group=root

[Install]
WantedBy=multi-user.target

sudo systemctl enable --now silod.service

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Logging

• Interactive run → stderr/stdout with ANSI colours.
• Background/service run → syslog (LOG_DAEMON), view with journalctl -t silod on systemd systems.

Set the log level with the RUST_LOG environment variable, e.g.:

sudo RUST_LOG=debug silod