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syslog-ng Premium Edition 7.0.14 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng PE quick-start guide The syslog-ng PE configuration file Collecting log messages — sources and source drivers
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) osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes 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 unix-stream, unix-dgram: Collecting messages from UNIX domain sockets windowsevent: Collecting Windows event logs
Sending and storing log messages — destinations and destination drivers
elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Event Collector file: Storing messages in plain-text files hdfs: Storing messages on the Hadoop Distributed File System (HDFS) http: Posting messages over HTTP kafka: Publishing messages to Apache Kafka logstore: Storing messages in encrypted files mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) pipe: Sending messages to named pipes program: Sending messages to external applications python: writing custom Python destinations smtp: Generating SMTP messages (e-mail) from logs splunk-hec: Sending messages to Splunk HTTP Event Collector sql: Storing messages in an SQL database stackdriver: Sending logs to the Google Stackdriver cloud 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) unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal — usertty() destination Client-side failover
Routing messages: log paths, flags, and filters Global options of syslog-ng PE TLS-encrypted message transfer Advanced Log Transfer Protocol Reliability and minimizing the loss of log messages Manipulating messages parser: Parse and segment structured messages Processing message content with a pattern database Correlating log messages Enriching log messages with external data Monitoring statistics and metrics of syslog-ng Multithreading and scaling in syslog-ng PE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages

unix-stream, unix-dgram: Collecting messages from UNIX domain sockets

The unix-stream() and unix-dgram() drivers open an AF_UNIX socket and start listening on it for messages. The unix-stream() driver is primarily used on Linux and uses SOCK_STREAM semantics (connection oriented, no messages are lost), while unix-dgram() is used on BSDs and uses SOCK_DGRAM semantics: this may result in lost local messages if the system is overloaded.

To avoid denial of service attacks when using connection-oriented protocols, the number of simultaneously accepted connections should be limited. This can be achieved using the max-connections() parameter. The default value of this parameter is quite strict, you might have to increase it on a busy system.

Both unix-stream and unix-dgram have a single required argument that specifies the filename of the socket to create. For the list of available optional parameters, see unix-stream() and unix-dgram() source options

unix-stream(filename [options]);
unix-dgram(filename [options]);


syslogd on Linux originally used SOCK_STREAM sockets, but some distributions switched to SOCK_DGRAM around 1999 to fix a possible DoS problem. On Linux you can choose to use whichever driver you like as syslog clients automatically detect the socket type being used.

Example: Using the unix-stream() and unix-dgram() drivers
source s_stream {
    unix-stream("/dev/log" max-connections(10));
source s_dgram {

windowsevent: Collecting Windows event logs

Event log messages collected by the Windows Event Collector for syslog-ng PE use this special source. To collect Windows event log messages, include this source in one of your source statements.

The Windows Event Collector tool for syslog-ng PE collects the log messages of Windows-based hosts in Unix datagram sockets, and then forwards them to a syslog-ng PE server over HTTPS (using TLS encryption and mutual authentication). syslog-ng PE reads the log messages using the windowsevent() source, and then parses the logs into key-value paris using the XML parser.

The XML parser uses the list-handling functionality to handle lists in the XML. Note that you cannot disable the list-handling functionality for the windowsevent() source.

For more information, see Windows Event Collector Administration Guide.

source s_wec {

Starting with version 7.0.13, the syslog-ng PE windowsevent() source can process XML arrays and make the elements of the arrays available as name-value pairs. For example, the following XML array becomes available as name-value pairs:

<Event xmlns="">
    <Data Name="SubjectUserSid">S-1-5-18</Data>
    <Data Name="SubjectUserName">WIN-K1678A68SQ6$</Data>

From the previous example, the following name-value pairs become available: ${Event.System.EventID} (5059), ${Event.EventData.SubjectUserSid} (S-1-5-18), ${Event.EventData.SubjectUserName} (WIN-K1678A68SQ6$).


The name-value pairs are only created from EventData.Data xml paths, that is, only for <Data> tags that are the children of an <EventData> tag and have the Name attribute.

If the array-like structure is not a Data tag under EventData tag, or it misses the Name attribute, then the regular XML-parser logic is used.

windowsevent() source options

The windowsevent() driver has the following options:

Type: string
Default: ".windowsevent."

Description: The prefix that you wish to append to the key-value pairs.

If you want to send Windows event logs to SDATA, then set prefix(".SDATA."). This can be useful, for example, when you forward Windows event logs to a syslog-ng Store Box.

Type: string
Default: /opt/syslog-ng/var/run/wec.sock

Description: The path to the Unix domain socket to read messages from.

Sending and storing log messages — destinations and destination drivers

A destination is where a log message is sent if the filtering rules match. Similarly to sources, destinations consist of one or more drivers, each defining where and how messages are sent.


If no drivers are defined for a destination, all messages sent to the destination are discarded. This is equivalent to omitting the destination from the log statement.

To define a destination, add a destination statement to the syslog-ng configuration file using the following syntax.

destination <identifier> {
Example: A simple destination statement

The following destination statement sends messages to the TCP port 1999 of the host.

destination d_demo_tcp {
    network("" port(1999));

If name resolution is configured, you can use the hostname of the target server as well.

destination d_tcp {
    network("target_host" port(1999));

  • Do not define the same drivers with the same parameters more than once, because it will cause problems. For example, do not open the same file in multiple destinations.

  • Do not use the same destination in different log paths, because it can cause problems with most destination types. Instead, use filters and log paths to avoid such situations.

  • Sources and destinations are initialized only when they are used in a log statement. For example, syslog-ng PE starts listening on a port or starts polling a file only if the source is used in a log statement. For details on creating log statements, see Routing messages: log paths, flags, and filters.

  • Hazard of data loss! If your log files are on an NFS-mounted network file system, see NFS file system for log files.

The following table lists the destination drivers available in syslog-ng PE.

Table 11: Destination drivers available in syslog-ng
Name Description
elasticsearch-http() Sends messages to an Elasticsearch server over HTTP using its REST API.
file() Writes messages to the specified file.
graphite() Sends metrics to a Graphite server to store numeric time-series data.
hdfs() Sends messages into a file on a Hadoop Distributed File System (HDFS) or MapR-FS node.
http() Sends messages over the HTTP protocol.
kafka() Publishes log messages to the Apache Kafka message bus, where subscribers can access them.
logstore() Writes messages securely into encrypted, compressed, and timestamped binary files.
mongodb() Sends messages to a MongoDB database.
network() Sends messages to a remote host using the BSD-syslog protocol over IPv4 and IPv6. Supports the TCP, UDP, ALTP, and TLS network protocols.
pipe() Writes messages to the specified named pipe.
program() Forks and launches the specified program, and sends messages to its standard input.
python() Send messages to a custom destination written in Python.
smtp() Sends e-mail messages to the specified recipients.
splunk-hec() Forward your log messages to Splunk.
sql() Sends messages into an SQL database. In addition to the standard syslog-ng packages, the sql() destination requires database-specific packages to be installed. Refer to the section appropriate for your platform in Installing syslog-ng.
syslog() Sends messages to the specified remote host using the IETF-syslog protocol. The IETF standard supports message transport using the UDP, TCP, and TLS networking protocols.
syslog-ng() The syslog-ng() destination driver forwards log messages to another syslog-ng node in EWMM format.
unix-dgram() Sends messages to the specified unix socket in SOCK_DGRAM style (BSD).
unix-stream() Sends messages to the specified unix socket in SOCK_STREAM style (Linux).
usertty() Sends messages to the terminal of the specified user, if the user is logged in.
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