ulog

USB serial port logger with automatic session management for Linux.

Features

• Logs serial data from USB devices with syslog-style timestamps
• Multi-device support - single service handles multiple USB devices
• Session tracking - each session gets a unique ID (format: MMDD-HHMM-xxxx)
• USB device identity - tracks vendor:product:serial to detect device swaps
• Export tool - list and export sessions by device, session ID, or USB identity
• Automatic daily log rotation (new folder per day)
• New log file on service restart
• Auto-start on device hotplug
• Config file changes auto-applied (no manual reload needed)
• Security hardened (dedicated user, systemd sandboxing, input validation)

Supported Systems

Linux distributions with systemd:

Distribution	Package
Arch Linux / Manjaro	AUR
Debian 11+ / Ubuntu 20.04+	.deb
Fedora / RHEL / CentOS	Manual
Other systemd-based	Manual

Requirements: Linux kernel 4.x+, systemd, bash 4.4+

Not supported: macOS, Windows, BSD, non-systemd Linux (OpenRC, runit, etc.)

Installation

Arch Linux (AUR)

yay -S ulog

Or manually:

git clone https://github.com/matterizelabs/ulog.git
cd ulog/packaging/arch
makepkg -si

Debian/Ubuntu

Download from releases:

sudo dpkg -i ulog_1.1.1_all.deb

Manual (root-only systems)

git clone https://github.com/matterizelabs/ulog.git
cd ulog
./install.sh

Configuration

Single Device (Simple)

Edit /etc/ulog.conf:

DEVICE=/dev/ttyUSB0
BAUD=115200
LOG_DIR=/var/log/ulog/ttyUSB0

Multiple Devices

Create a config file per device in /etc/ulog.d/:

# /etc/ulog.d/sensor1.conf
DEVICE=/dev/ttyUSB0
BAUD=115200

# /etc/ulog.d/sensor2.conf
DEVICE=/dev/ttyUSB1
BAUD=9600

# /etc/ulog.d/gps.conf
DEVICE=/dev/ttyACM0
BAUD=38400

Each device gets its own log directory: /var/log/ulog/<device_name>/

Changes are auto-applied when config files are saved.

Usage

Enable and start:

systemctl enable --now ulog.service ulog-rollover.timer ulog-genconfig.path

View logs:

# Single device
tail -f /var/log/ulog/ttyUSB0/$(date +%Y-%m-%d)/*.log

# All devices
tail -f /var/log/ulog/*/$(date +%Y-%m-%d)/*.log

Check status:

systemctl status ulog.service
journalctl -u ulog.service -f

Session Management

Each logging session is assigned a unique ID in the format MMDD-HHMM-xxxx (e.g., 0120-1830-a1b2). Sessions are tracked in a session.index file per device with start/end times and USB device identity.

USB Device Identity

ulog tracks the USB vendor ID, product ID, and serial number for each device. This allows:

• Detecting when a different physical device is connected to the same port
• Filtering exports by specific hardware (useful with multiple identical adapters)

Identity format: vendor:product:serial (e.g., 10c4:ea60:0001a2b3)

List Sessions

# List all sessions for a device
ulog-export --list --device ttyUSB0

# List sessions from all devices
ulog-export --list --all

Output:

SESSION            START                  END                       IDENTITY             FILES
====================================================================================================
0120-1830-a1b2     2026-01-20 18:30:00    2026-01-20 19:45:00       10c4:ea60:0001a2b3   2 file(s)
0120-2000-c3d4     2026-01-20 20:00:00    ongoing                   10c4:ea60:0001a2b3   1 file(s)

Export Sessions

# Export specific session
ulog-export --session 0120-1830-a1b2 --device ttyUSB0 --output session.log

# Export latest/current session
ulog-export --device ttyUSB0 --output latest.log

# Export multiple sessions combined
ulog-export --session 0120-1830-a1b2,0120-2000-c3d4 --device ttyUSB0 --output combined.log

Filter by USB Identity

# Export all sessions from Silicon Labs adapters (vendor 10c4)
ulog-export --vendor 10c4 --output silabs.log

# Export from specific vendor and product (CP210x)
ulog-export --vendor 10c4 --product ea60 --output cp210x.log

# Export from specific physical device (by serial, prefix match)
ulog-export --vendor 10c4 --product ea60 --serial 0001a2b3 --output device1.log

Add a new device:

cat > /etc/ulog.d/mydevice.conf << EOF
DEVICE=/dev/ttyUSB2
BAUD=115200
EOF
chown root:ulog /etc/ulog.d/mydevice.conf
chmod 0640 /etc/ulog.d/mydevice.conf
# Service auto-restarts to pick up new device

Log Format

Logs use syslog-style timestamps:

Jan 18 14:30:00 sensor reading: 42.5
Jan 18 14:30:01 sensor reading: 43.1

Log Directory Structure

/var/log/ulog/
  ttyUSB0/
    session.index         # Session tracking database
    2026-01-18/
      2026-01-18_14-30-00.log
    2026-01-19/
      2026-01-19_00-00-01.log
  ttyUSB1/
    session.index
    2026-01-18/
      2026-01-18_14-30-00.log
  ttyACM0/
    ...

/var/lib/ulog/
  sessions/               # Runtime state
    ttyUSB0.session       # Current session ID
    ttyUSB0.identity      # Last known USB identity

Configuration Reference

Key	Description	Default
DEVICE	Serial device path	/dev/ttyUSB0
BAUD	Baud rate (300-921600)	115200
LOG_DIR	Log directory (must be under /var/log/)	/var/log/ulog/<device>

Valid baud rates: 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600

Project Structure

ulog/
  src/                    # Source files
    ulog.sh               # Main logger script (multi-device)
    ulog-export           # Session export/list tool
    ulog-genconfig        # Config generator
    ulog.conf             # Default configuration
  services/               # Systemd units
    ulog-genconfig.path   # Watch config for changes
    ulog-genconfig.service
    ulog-rollover.service
    ulog-rollover.timer
  packaging/              # Distribution packages
    arch/                 # Arch Linux (AUR)
    debian/               # Debian/Ubuntu

Security

• Runs as dedicated ulog user (not root)
• Systemd sandboxing (ProtectSystem, PrivateTmp, NoNewPrivileges)
• Input validation on all config values
• Config files must be root-owned (0640)
• Device paths strictly validated
• See SECURITY.md for details

Dependencies

• socat
• moreutils (provides ts)
• coreutils (provides realpath)

License

MIT