syslog-ng Open Source Edition 3.16 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local e-mail messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP elasticsearch: Sending messages directly to Elasticsearch version 1.x elasticsearch2: Sending logs directly to Elasticsearch and Kibana 2.0 or higher file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka loggly: Using Loggly logmatic: Using mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann smtp: Generating SMTP messages (e-mail) from logs Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng: Forwarding messages and tags to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages db-parser: Process message content with a pattern database (patterndb) Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Third-party contributions Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License About us

Modules in syslog-ng OSE

The syslog-ng OSE application is modular, to increase its flexibility and also to simplify the development of additional modules. Most of the functionality of syslog-ng OSE is in separate modules. That way it becomes also possible to finetune the resource requirements of syslog-ng OSE, for example, by loading only the modules that are actually used in the configuration, or simply omitting modules that are not used but require large amount of memory.

Each module contains one or more plugins, which add some functionality to syslog-ng OSE, for example, a destination or a source driver.

  • To display the list of available modules, execute the syslog-ng --version command.

  • To the description of the available modules, execute the syslog-ng --module-registry command.

  • To customize which modules are loaded automatically when syslog-ng OSE is started, use the --default-modules command-line option of syslog-ng OSE.

  • To request loading a module from the syslog-ng OSE configuration file, see Loading modules.

For details on the command-line parameters of syslog-ng OSE mentioned in the previous list, see the syslog-ng OSE man page at The syslog-ng manual page.

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Loading modules

The syslog-ng Open Source Edition application loads every available module during startup.

To load a module that is not loaded automatically, include the following statement in the syslog-ng OSE configuration file:

@module <module-name>

Note the following points about the @module statement:

  • The @module statement is a top-level statement, that is, it cannot be nested into any other statement. Usually it is used immediately after the @version statement.

  • Every @module statement loads a single module: loading multiple modules requires a separate @module statement for every module.

  • In the configuration file, the @module statement of a module must be earlier than the module is used.


To disable loading every module automatically, set the autoload-compiled-modules global variable to 0 in your configuration file:

@define autoload-compiled-modules 0

Note that in this case, you have to explicitly load the modules you want to use.

Use the @requires statement to ensure that the specified module is loaded

To ensure that a module is loaded, include the following statement in the syslog-ng OSE configuration file or the external files included in the configuration file:

@requires <module-name>


If you include the @requires statement in the:

  • syslog-ng OSE configuration file, syslog-ng OSE attempts to load the required module. If it fails to load the module, syslog-ng OSE stops and an error message is displayed.
  • external files included in the configuration file, syslog-ng OSE attempts to load the required module. If it fails to load the module, only the external file is not processed.

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Managing complex syslog-ng configurations

The following sections describe some methods that can be useful to simplify the management of large-scale syslog-ng installations.

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Including configuration files

The syslog-ng application supports including external files in its configuration file, so parts of its configuration can be managed separately. To include the contents of a file in the syslog-ng configuration, use the following syntax:

@include "<filename>"

This imports the entire file into the configuration of syslog-ng OSE, at the location of the include statement. The <filename> can be one of the following:

  • A filename, optionally with full path. The filename (not the path) can include UNIX-style wildcard characters (*, ?). When using wildcard characters, syslog-ng OSE will include every matching file. For details on using wildcard characters, see glob.

  • A directory. When including a directory, syslog-ng OSE will try to include every file from the directory, except files beginning with a ~ (tilde) or a . (dot) character. Including a directory is not recursive. The files are included in alphabetic order, first files beginning with uppercase characters, then files beginning with lowercase characters. For example, if the directory contains the a.conf, B. conf, c.conf, D.conf files, they will be included in the following order: B.conf, D. conf, a.conf, c.conf.

When including configuration files, consider the following points:

  • Defining an object twice is not allowed, unless you use the @define allow-config-dups 1 definition in the configuration file. If an object is defined twice (for example the original syslog-ng configuration file and the file imported into this configuration file both define the same option, source, or other object), then the object that is defined later in the configuration file will be effective. For example, if you set a global option at the beginning of the configuration file, and later include a file that defines the same option with a different value, then the option defined in the imported file will be used.

  • Files can be embedded into each other: the included files can contain include statements as well, up to a maximum depth of 15 levels.

  • You cannot include complete configuration files into each other, only configuration snippets can be included. This means that the included file cannot have a @version statement.

  • Include statements can only be used at top level of the configuration file. For example, the following is correct:

    @version: 3.16
    @include "example.conf"

    But the following is not:

    source s_example {
        @include "example.conf"


The syslog-ng application will not start if it cannot find a file that is to be included in its configuration. Always double-check the filenames, paths, and access rights when including configuration files, and use the --syntax-only command-line option to check your configuration.

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