syslog-ng Premium Edition 6.0.21 - Administration Guide

The main body of the configuration file consists of object definitions: sources, destinations, log paths define which log message are received and where they are sent. All identifiers, option names and attributes, and any other strings used in the syslog-ng configuration file are case sensitive. Objects must be defined before they are referenced in another statement. Object definitions (also called statements) have the following syntax:

object_type object_id {<options>};

For example, the following line defines a source and calls it s_internal.

source s_internal { internal(); };

The object can be later referenced in other statements using its ID, for example, the previous source is used as a parameter of the following log statement:

log { source(s_internal); destination(d_file); };

The parameters and options within a statement are similar to function calls of the C programming language: the name of the option followed by a list of its parameters enclosed within brackets and terminated with a semicolon.

option(parameter1, parameter2); option2(parameter1, parameter2);

For example, the file() driver in the following source statement has three options: the filename (/var/log/apache/access.log), follow-freq(), and flags(). The follow-freq() option also has a parameter, while the flags() option has two parameters.

source s_tail { file("/var/log/apache/access.log"
    follow-freq(1) flags(no-parse, validate-utf8)); };

Objects may have required and optional parameters. Required parameters are positional, meaning that they must be specified in a defined order. Optional parameters can be specified in any order using the option(value) format. If a parameter (optional or required) is not specified, its default value is used. The parameters and their default values are listed in the reference section of the particular object.

source s_demo_stream1 {
        unix-stream("<path-to-socket>" max-connections(10) group(log)); };
source s_demo_stream2 {
        unix-stream("<path-to-socket>" group(log) max-connections(10)); };

Some options are global options, or can be set globally, for example, whether syslog-ng PE should use DNS resolution to resolve IP addresses. Global options are detailed in Chapter 9, Global options of syslog-ng PE.

options { use-dns(no); };

All identifiers, attributes, and any other strings used in the syslog-ng configuration file are case sensitive.

Objects can be used before definition.

To add comments to the configuration file, start a line with # and write your comments. These lines are ignored by syslog-ng.

# Comment: This is a stream source
source s_demo_stream {
        unix-stream("<path-to-socket>" max-connections(10) group(log)); };

The configuration file can contain a maximum of 6665 source / destination / log elements.

When writing the names of options and parameters (or other reserved words), the hyphen (-) and underscore (_) characters are equivalent, for example max-connections(10) and max_connections(10) are both correct.

Numbers can be prefixed with + or - to indicate positive or negative values. Numbers beginning with zero (0) or 0x are treated as octal or hexadecimal numbers, respectively.

You can use commas (,) to separate options or other parameters for readability, syslog-ng completely ignores them. The following declarations are equivalent:

source s_demo_stream {
        unix-stream("<path-to-socket>" max-connections(10) group(log)); };
source s_demo_stream {
        unix-stream("<path-to-socket>", max-connections(10), group(log)); };

When enclosing object IDs (for example the name of a destination) between double-quotes ("mydestination"), the ID can include whitespace as well, for example:

source "s demo stream" {
        unix-stream("<path-to-socket>" max-connections(10) group(log)); };

For notes on using regular expressions, see the section called “Regular expressions”.

Without any quotes, as long as the value does not contain any spaces or special characters. In other word, it contains only the following characters: a-zA-Z0-9_..

Between apostrophes, in case the value does not contain apostrophes.

Between double quotes, in which case special characters must be escaped using backslashes (\).