syslog-ng Open Source Edition 3.16 - Administration Guide

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.

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.

@define autoload-compiled-modules 0

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>

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.

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"
  };