syslog-ng Open Source Edition 3.22 - Administration Guide

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:

• The default path where syslog-ng OSE looks for the file depends on where syslog-ng OSE is installed. The syslog-ng --version command displays this path as Include-Path.

• 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: 3.22
  @include "example.conf"

  But the following is not:

  source s_example {
      @include "example.conf"
  };

Reusing configuration blocks

To create a reusable configuration snippet and reuse parts of a configuration file, you have to define the block (for example, a source) once, and reference it later. (Such reusable blocks are sometimes called a Source Configuration Library, or SCL.) Any syslog-ng object can be a block. Use the following syntax to define a block:

block type name() {<contents of the block>};

Type must be one of the following: destination, filter, log, options, parser, rewrite, root, source. The root blocks can be used in the "root" context of the configuration file, that is, outside any other statements.

Note that options can be used in blocks only in version 3.22 and later.

Blocks may be nested into each other, so for example a block can be built from other blocks. Blocks are somewhat similar to C++ templates.

The type and name combination of each block must be unique, that is, two blocks can have the same name if their type is different.

To use a block in your configuration file, you have to do two things:

• Include the file defining the block in the syslog-ng.conf file — or a file already included into syslog-ng.conf. Version 3.7 and newer automatically includes the *.conf files from the <directory-where-syslog-ng-is-installed>/scl/*/ directories.

• Reference the name of the block in your configuration file. This will insert the block into your configuration. For example, to use a block called myblock, include the following line in your configuration:

  myblock()

  Blocks may have parameters, but even if they do not, the reference must include opening and closing parentheses like in the previous example.

The contents of the block will be inserted into the configuration when syslog-ng OSE is started or reloaded.

block source myappsource() {
        file("/opt/var/myapplication.log" follow-freq(1) default-facility(syslog)); };

@version: 3.22
@include "<correct/path>/myblocks.conf"
source s_myappsource { myappsource(); };
...
log { source(s_myappsource); destination(...); };

To define a block that defines more than one object, use root as the type of the block, and reference the block from the main part of the syslog-ng OSE configuration file.

block root mylogs() {
    source s_file {
        file("/var/log/mylogs.log" follow-freq(1));
    };
    destination d_local {
        file("/var/log/messages");
    };
    log {
        source(s_file); destination(d_local);
    };
};

block source my_tcp_source(localport() flags("")) {
    network(port(`localport`) transport(tcp) flags(`flags`));
};

my_tcp_source(localport(8080))

network(port(8080) transport(tcp) flags());

block type block_name(argument1(<default-value-of-the-argument>) argument2(<default-value-of-the-argument>) argument3())

block source s_logfile (filename("messages")) {
    file("/var/log/`filename`" );
};

source s_example {
    s_logfile(filename("logfile.log"));
};

block source s_logfile(filename("messages") ...) {
    file("/var/log/`filename`" `__VARARGS__`);
};

source s_example {
    s_logfile(
        filename("logfile.log")
        follow-freq(1)
        flags(no-parse)
    );
};

block source pacct(file("/var/log/account/pacct") follow-freq(1) ...) {
    @module pacctformat
    file("`file`" follow-freq(`follow-freq`) format("pacct") tags(".pacct") `__VARARGS__`);
};

block options setup-dns(use-dns()) {
    keep-hostname(no);
    use-dns(`use-dns`);
    use-fqdn(`use-dns`);
dns-cache(`use-dns`);
};

options {
    setup-dns(use-dns(yes));
};