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syslog-ng Open Source Edition 3.25 - 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 linux-audit: Collecting messages from Linux audit logs network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local email 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 python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources 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 collectd: sending metrics to collectd elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Bulk API 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 (Java implementation) kafka: Publishing messages to Apache Kafka (C implementation, using the librdkafka client) loggly: Using Loggly logmatic: Using Logmatic.io 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() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (email) from logs snmp: Sending SNMP traps 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(): Forward logs 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 Client-side failover
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 Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License Glossary

Notes about the configuration syntax

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 3.5, you can use suffixes for kilo-, mega-, and gigabytes. Use the Kb, Mb, or Gb suffixes for the base-10 version, and Kib, Mib, or Gib for the base-2 version. That is, 2MB means 2000000, while 2MiB means 2097152. For example, to set the log-msg-size() option to 2000000 bytes, use log-msg-size(2Mb).

  • 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.

Defining configuration objects inline

Starting with syslog-ng OSE 3.4, you can define configuration objects inline, where they are actually used, without having to define them in a separate placement. This is useful if you need an object only once, for example, a filter or a rewrite rule. Every object can be defined inline: sources, destinations, filters, parsers, rewrite rules, and so on.

To define an object inline, use braces instead of parentheses. That is, instead of <object-type> (<object-id>);, you use <object-type> {<object-definition>};

Example: Using inline definitions

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");
    };
};

Using channels in configuration objects

Starting with syslog-ng OSE3.4, every configuration object is a log expression. Every configuration object is essentially a configuration block, and can include multiple objects. To reference the block, only the top-level object must be referenced. That way you can use embedded log statements, junctions and in-line object definitions within source, destination, filter, rewrite and parser definitions. For example, a source can include a rewrite rule to modify the messages received by the source, and that combination can be used as a simple source in a log statement. This feature allows you to preprocess the log messages very close to the source itself.

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>
    };
};
Example: Using channels

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.

NOTE:

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);
        };
    };
};

Global and environmental variables

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 (\).

TIP:

The environmental variables of the host are automatically imported and can be used as global variables.

In syslog-ng OSE 3.24 and later, the location of the syslog-ng configuration file is available as the `syslog-ng-sysconfdir` variable.

Example: Using global variables

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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