Well, no doubt logging is the nervous system of any IT infrastructure. From troubleshooting outages to satisfying compliance audits and threat management, having the right log management pipeline can make the difference between smooth operations and chaotic firefighting. For decades, syslog-ng and rsyslog have been two of the most widely used log management tools for Unix and Linux environments. Both provide implementations of the original 1980s syslog protocol and are designed to collect, process, and forward log messages across networks.
At first glance, these two tools look similar: they share the same goal and offer comparable capabilities, such as support for structured data formats, flexible filtering, transformations, and multiple transport protocols. However, the differences between them become evident when you dive into their configuration models, performance characteristics, scalability, and ecosystem support.
In this article we will walk through the strengths and weaknesses of syslog-ng and rsyslog, highlight their differences, so finally you can decide which to go with, building your log shipping and telemetry management over in heterogeneous, cloud-native and hybrid environments.
The origins of syslog, rsyslog and syslog-ng
Before diving into the details, it’s worth revisiting where these tools came from.
The syslog protocol originated in the 1980s as part of the Unix operating system.
Initially, syslog was a very simple way for daemons and applications to write log messages into a centralized logging service.
Messages were tagged with a priority and facility and then written to a flat text file, typically /var/log/syslog.
Over time, as networks grew and distributed systems became the norm, syslog evolved into a network log forwarding protocol. It was standardized under RFC 3164 (informal) and later RFC 5424 (formal, supporting structured data and UTF-8).
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syslog-ng (developed in 1998 by Balabit, now One Identity) was one of the first major enhancements to the original syslogd daemon. Its goal was to modernize syslog by adding stronger filtering, modular configuration, and support for secure transports like TLS.
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rsyslog (created in 2004 by Rainer Gerhards) started as a drop-in replacement for syslogd, but quickly grew into a high-performance log processing engine with advanced features such as database logging, encryption, and support for massive message throughput.
Today, both remain popular — often bundled by default in Linux distributions — but they tend to appeal to slightly different user bases.
syslog-ng: A flexible and modular log daemon
syslog-ng is often described as the "Swiss army knife" of log management. It takes the simplicity of syslogd and extends it with modular configuration blocks that allow precise control over how logs are collected, parsed, filtered, and routed.
Key features of syslog-ng:
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Modular and highly configurable: Its configuration language is expressive, enabling fine-grained control over log flows.
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Structured logging: Natively supports JSON and other structured formats, making it easier to forward logs into SIEMs and analytics platforms.
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Advanced filtering and parsing: Complex conditions can be applied to determine where and how messages are routed.
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High reliability under load: syslog-ng has been tested extensively in large-scale enterprise environments.
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Security features: Native support for TLS encryption, mutual authentication, and digital signatures.
To better understand its role, let’s look at the strengths that make syslog-ng a good fit for enterprises, as well as some drawbacks you may encounter.
| Pros of syslog-ng | Cons of syslog-ng |
|---|---|
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You may find syslog-ng applicable in typical use cases such as:
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Enterprises needing custom log routing and filtering.
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Environments with mixed log formats that need normalization.
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Security-conscious organizations requiring TLS and message integrity validation.
rsyslog: A high-performance logging powerhouse
rsyslog has become the default logging daemon in many Linux distributions, including Red Hat Enterprise Linux, Ubuntu, and Debian. While it started as a syslogd replacement, its scope grew into a high-performance event processor capable of handling millions of log messages per second.
Key features of rsyslog:
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Multi-protocol support — Handles UDP, TCP, and RELP (Reliable Event Logging Protocol) for guaranteed delivery.
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High throughput — Optimized for speed, often outperforming syslog-ng in benchmarks.
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Extensibility — Rich ecosystem of plugins for inputs, outputs, and processing.
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Structured data handling — Supports JSON, CEE, and other formats.
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Database integration — Can log directly into MySQL, PostgreSQL, or MongoDB.
Now, let’s explore where rsyslog really shines and where it may present challenges.
| Pros of rsyslog | Cons of rsyslog |
|---|---|
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Typical use cases for rsyslog may be summarized as follows:
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High-throughput environments (telecoms, ISPs, cloud-scale systems).
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Database logging when applications require direct persistence.
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Linux admins who want a default, well-supported logging stack without external dependencies.
syslog-ng vs rsyslog: A side-by-side comparison
| Feature or aspect | syslog-ng | rsyslog |
|---|---|---|
First Release |
1998 |
2004 |
Design Focus |
Flexibility & filtering |
Performance & reliability |
Config Language |
Domain-specific (DSL) |
Traditional, rule-based syntax |
Protocol Support |
UDP, TCP, TLS, RFC5424 |
UDP, TCP, RELP, TLS, RFC5424 |
Structured Data |
JSON, XML, custom formats |
JSON, CEE, custom formats |
Database Logging |
Limited support |
Strong (MySQL, PostgreSQL, MongoDB) |
Cross-Platform |
Linux/Unix, minimal Windows |
Linux/Unix, minimal Windows |
Performance |
Good, scalable |
Very high (millions of EPS) |
Ease of Use |
Moderate to difficult |
Moderate to difficult |
Best Fit |
Enterprises with custom routing |
High-performance, large volumes |
Another option to consider: NXLog Platform
While syslog-ng and rsyslog remain excellent choices for traditional Unix/Linux systems, modern IT environments often span Windows, Linux, macOS, cloud VMs, and containers. This is where NXLog Platform and NXLog Agent stand out. Unlike the Unix-centric daemons, NXLog Agent is a true cross-platform log and telemetry shipper, supporting:
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Operating systems: Windows, Linux, macOS, Solaris, AIX, FreeBSD (x32/x64, ARM).
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Log sources and formats: Windows Event Logs, syslog, JSON, XML, CEF, and more.
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Destinations: SIEMs, APM tools, observability platforms (Splunk, Elasticsearch, Datadog, etc.)
You may consider NXLog Platform and the bundled NXLog Agent for a set of reasons:
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Cross-platform by design: No need to run different tools for different OSes.
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Performance: Efficient parsing and routing with minimal CPU/memory overhead.
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Security-first: Built-in TLS/SSL encryption and authentication.
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Extended functionality: File integrity monitoring (FIM), trace/metric collection, and compliance support (PCI DSS, HIPAA, SOX).
Conclusion
Both syslog-ng and rsyslog have proven their worth as battle-tested, reliable log shippers in Unix/Linux infrastructures of any scale and grade. Choose syslog-ng if you need complex filtering, structured data handling, and enterprise-grade security features. If raw performance, scalability, and reliable delivery are your top priorities - you could opt to rsyslog.
However, for organizations running hybrid, multi-OS, or cloud-native environments, neither tool fully addresses the challenges of cross-platform telemetry. In these cases, a more modern telemetry pipeline solution like NXLog Platform offers the flexibility, performance, and coverage required to unify logging across diverse systems, formats, protocols or integrations.
Frequently asked questions (FAQ)
Q: Which is easier to configure: rsyslog or syslog-ng?
A: Both have a learning curve. syslog-ng uses a domain-specific configuration language that can feel intuitive once learned, but it is verbose. rsyslog relies on a rule-based syntax that can be cryptic at first but is widely documented. For simple setups, rsyslog might feel quicker, but for complex pipelines, syslog-ng often offers clearer logic.
Q: Can I use rsyslog or syslog-ng on Windows?
A: Both tools are primarily designed for Unix/Linux environments. While there are limited ports for Windows, they are not widely supported. For production-grade Windows logging, a cross-platform agent like NXLog Agent is usually a better choice.
Q: Which tool performs better under heavy load?
A: rsyslog generally outperforms syslog-ng in benchmarks, especially when handling millions of events per second. This is due to its RELP protocol support and optimized buffering. However, syslog-ng is still highly reliable and more than capable of handling large-scale enterprise workloads.
Q: Do syslog-ng and rsyslog support modern log formats like JSON?
A: Yes, both support structured log formats such as JSON, CEE, and XML. This makes them compatible with modern observability and SIEM platforms, which expect structured data instead of plain text logs.
Q: Should I replace syslog-ng or rsyslog with NXLog Platform?
A: Not necessarily. If your infrastructure is Unix/Linux-only and your current setup works, sticking with rsyslog or syslog-ng may be fine. However, if you run a hybrid environment (Windows, Linux, cloud, containers) and need advanced features like file integrity monitoring, metrics, or compliance support, NXLog Platform provides a unified and more scalable solution. Also, migrating to NXLog Platform is seamless whatever endpoints (like SIEM) your existing pipeline has.
