Introduction

journald and syslog are two popular logging systems used in Linux environments. While they share some similarities, they have distinct differences in their design, functionality, and use cases.

Overview

journald

• Introduced by systemd, a system and service manager for Linux operating systems.
• Designed to provide a more modern, efficient, and feature-rich logging system.
• Stores log messages in a binary format, allowing for faster querying and indexing.
• Supports structured logging, enabling easier parsing and analysis of log data.
• Integrates well with other systemd components, such as systemctl and systemd-analyze.

To learn more about using journald, check out our guide on What is Journald and how to do centralized journald logging

syslog

• A traditional logging system that has been widely used in Unix-like systems for decades.
• Uses a plain text format for storing log messages, making it easy to read and parse.
• Supports remote logging, allowing log messages to be sent to a central log server.
• Has a wide range of implementations, including rsyslog, syslog-ng, and syslogd.

To learn more about using syslog, check out our guide on Parsing Syslog Messages

Key Differences

1. Log format: journald uses a binary format, while syslog uses plain text.
2. Structured logging: journald supports structured logging, making it easier to parse and analyze log data. Syslog does not have built-in support for structured logging.
3. Performance: journald is designed for performance and can handle high volumes of log messages. Syslog can become bottlenecked under heavy loads.
4. Integration: journald is tightly integrated with systemd, making it a good choice for systems that use systemd. Syslog is more widely supported and can be used with various system managers.
5. Remote logging: Syslog has built-in support for remote logging, while journald relies on external tools.
6. Log rotation: journald automatically rotates logs based on size and time, while syslog requires manual configuration for log rotation.

Choosing Between journald and syslog

1. Use journald:
   • If you're running a systemd-based system and want a modern, efficient logging system.
   • If you need structured logging and easy parsing of log data.
   • If you prioritize performance and security.
2. Use syslog:
   • If you need to support legacy systems or applications that rely on traditional syslog.
   • If you require remote logging capabilities without additional tools.
   • If you prefer a widely supported, plain-text logging format.

For the most part, you will be using both the systems in conjunction with each other. journald is the default logging system on most linux systems these days. Most networking devices will log to syslog though. You could even forward journal logs to syslog by configuring journald using below setting.

[ForwardToSyslog]
yes

To learn more about journald configuration, check out our guide on journald configuration

Conclusion

journald and syslog are both popular logging systems used in Linux environments. While they have some similarities, they are designed for different use cases and have distinct differences in their functionality and features.