Logging Daemon (logd)

Overview

The Logging Daemon (logd) provides centralized logging services for FreeWorld OS, collecting and managing log messages from all system components. It handles log rotation, filtering, and archival.

Features

• Log Message Collection: Receives log entries from all system components
• Log File Rotation: Automatically rotates logs when size limit reached
• Log Level Filtering: Filters logs by severity level (DEBUG, INFO, WARNING, ERROR, CRITICAL)
• Log Archival: Maintains multiple rotated log files
• Structured Logging: Timestamp, level, source, PID, and message
• Daemon Mode: Runs as background daemon

Log Levels

Log Format

Log entries are written in the following format:

[YYYY-MM-DD HH:MM:SS] [LEVEL] [SOURCE] [PID:####] Message text

Example:

[2024-01-15 10:30:45] [INFO] [kernel] [PID:1] Kernel initialized successfully
[2024-01-15 10:30:46] [ERROR] [networkd] [PID:42] Failed to configure interface eth0

Configuration

logd can be configured via command-line arguments:

• --no-daemon - Run in foreground (for debugging)
• --log-dir <path> - Set log directory (default: /var/log)
• --max-size <MB> - Maximum log file size in MB (default: 10MB)
• --min-level <LEVEL> - Minimum log level to record (default: INFO)

Log Rotation

When a log file reaches the maximum size, logd automatically rotates it:

1. Current log (system.log) is renamed to system.log.1
2. Existing rotated logs are shifted (system.log.1 → system.log.2, etc.)
3. Oldest log files beyond the limit are deleted
4. A new system.log is created

Default: Keeps up to 10 rotated log files

IPC Interface

Components send log entries to logd via IPC (stdin in current implementation). The format is:

LEVEL|SOURCE|PID|MESSAGE

Example:

INFO|kernel|1|Kernel initialized
ERROR|networkd|42|Failed to configure interface

Future: Will use Unix domain sockets or named pipes for better IPC

Usage

Starting logd

# Start as daemon (default)
logd

# Start in foreground for debugging
logd --no-daemon

# Custom configuration
logd --log-dir /custom/logs --max-size 50 --min-level WARNING

Sending Log Entries

# From a C program
printf("INFO|myapp|%d|Application started\n", getpid()) | logd

# From shell script
echo "WARNING|script|$$|Disk space low" | logd

File Structure

services/logd/
├── logd.c          # Main daemon implementation
└── Makefile        # Build system

Integration

logd integrates with:

• Kernel Logger: Receives kernel log messages
• System Services: All services send logs to logd
• Applications: User applications can send logs via IPC
• System Monitor: Can read log files for monitoring

Status