What is the difference between system log and other log files in Linux?

Understanding System Logs and Other Log Files in Linux

In the Linux operating system, log files play a crucial role in providing information about the system's activities, errors, and events. These log files can be categorized into two main types: system logs and other log files.

System Logs

System logs, also known as system journal or systemd logs, are the primary logs maintained by the Linux operating system. These logs contain information about the overall system's behavior, including:

Boot and Shutdown Events: System logs record the details of when the system was booted up and when it was shut down.
Kernel Messages: The system logs capture messages from the Linux kernel, which is the core of the operating system. These messages can include information about hardware initialization, driver activities, and kernel-level errors.
Service and Daemon Logs: System logs record the activities and events related to various system services and daemons (background processes) running on the Linux system.
Security-related Events: The system logs may include information about security-related events, such as failed login attempts, unauthorized access attempts, and other security-relevant occurrences.

System logs are typically managed by the systemd service, which is the default init system and service manager in many modern Linux distributions. The systemd service provides a centralized logging mechanism known as the "systemd journal," which collects and organizes the system's log entries.

Other Log Files

In addition to the system logs, Linux also maintains various other log files that provide more detailed information about specific applications, services, or system components. These log files are typically stored in the /var/log directory and can include:

Application Logs: These logs contain information about the activities and events of specific applications running on the Linux system, such as web servers, database management systems, or custom-developed software.
Service Logs: Similar to application logs, service logs provide detailed information about the operation of various system services, such as the network service, the cron job scheduler, or the SSH server.
Error Logs: These logs capture information about errors, warnings, and other issues that have occurred within the system or specific applications.
Access Logs: Access logs record information about user access to various system resources, such as web server logs or user login/logout events.

Unlike the centralized system logs managed by systemd, these other log files are typically managed by the individual applications or services that generate them. The location, format, and content of these logs can vary depending on the specific software or service.

graph TB A[Linux Operating System] B[System Logs] B1[Boot and Shutdown Events] B2[Kernel Messages] B3[Service and Daemon Logs] B4[Security-related Events] C[Other Log Files] C1[Application Logs] C2[Service Logs] C3[Error Logs] C4[Access Logs] A --> B A --> C

In summary, the key difference between system logs and other log files in Linux is the scope and centralization of the information they contain. System logs provide a comprehensive overview of the system's overall behavior and events, while other log files focus on more specific applications, services, or system components. Understanding the purpose and location of these different log files can be crucial for effectively troubleshooting and monitoring a Linux system.