When you are editing the syslog-ng configuration file, note the following points:
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.
Starting with syslog-ng OSE version
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 Regular expressions.
You can use if {}, elif {}, and else {} blocks to configure conditional expressions. For details, see if-else-elif: Conditional expressions.
Starting with syslog-ng OSE
To define an object inline, use braces instead of parentheses. That is, instead of <object-type> (<object-id>);, you use <object-type> {<object-definition>};
The following two configuration examples are equivalent. The first one uses traditional statements, while the second uses inline definitions.
source s_local { system(); internal(); }; destination d_local { file("/var/log/messages"); }; log { source(s_local); destination(d_local); };
log { source { system(); internal(); }; destination { file("/var/log/messages"); }; };
Starting with syslog-ng OSE
To embed multiple objects into a configuration object, use the following syntax. Note that you must enclose the configuration block between braces instead of parenthesis.
<type-of-top-level-object> <name-of-top-level-object> { channel { <configuration-objects> }; };
For example, to process a log file in a specific way, you can define the required processing rules (parsers and rewrite expressions) and combine them in a single object:
source s_apache { channel { source { file("/var/log/apache/error.log"); }; parser(p_apache_parser); }; }; log { source(s_apache); ... };
The s_apache source uses a file source (the error log of an Apache webserver) and references a specific parser to process the messages of the error log. The log statement references only the s_apache source, and any other object in the log statement can already use the results of the p_apache_parserparser.
You must start the object definition with a channel even if you will use a junction, for example:
parser demo-parser() { channel { junction { channel { ... }; channel { ... }; }; }; };
If you want to embed configuration objects into sources or destinations, always use channels, otherwise the source or destination will not behave as expected. For example, the following configuration is good:
source s_filtered_hosts { channel{ source { pipe("/dev/pipe"); syslog(ip(192.168.0.1) transport("tcp")); syslog(ip(127.0.0.1) transport("tcp")); }; filter { netmask(10.0.0.0/16); }; }; };
You can define global variables in the configuration file. Global variables are actually name-value pairs. When syslog-ng processes the configuration file during startup, it automatically replaces `name` with value. To define a global variable, use the following syntax:
@define name "value"
The value can be any string, but special characters must be escaped (for details, see Regular expressions). To use the variable, insert the name of the variable enclosed between backticks (`, similarly to using variables in Linux or UNIX shells) anywhere in the configuration file. If backticks are meant literally, repeat the backticks to escape them. For example, ``not-substituted-value``.
The value of the global variable can be also specified using the following methods:
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 (\).
The environmental variables of the host are automatically imported and can be used as global variables.
In syslog-ng OSE
For example, if an application is creating multiple log files in a directory, you can store the path in a global variable, and use it in your source definitions.
@define mypath "/opt/myapp/logs" source s_myapp_1 { file("`mypath`/access.log" follow-freq(1)); }; source s_myapp_2 { file("`mypath`/error.log" follow-freq(1)); }; source s_myapp_3 { file("`mypath`/debug.log" follow-freq(1)); };
The syslog-ng OSE application will interpret this as:
@define mypath "/opt/myapp/logs" source s_myapp_1 { file("/opt/myapp/logs/access.log" follow-freq(1)); }; source s_myapp_2 { file("/opt/myapp/logs/error.log" follow-freq(1)); }; source s_myapp_3 { file("/opt/myapp/logs/debug.log" follow-freq(1)); };
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