syslog-ng Open Source Edition 3.37 - 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 kubernetes: Collecting and parsing the Kubernetes CRI (Container Runtime Interface) format linux-audit: Collecting messages from Linux audit logs mqtt: receiving messages from an MQTT broker 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 discord: Sending alerts and notifications to Discord 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-c(): Publishing messages to Apache Kafka using the librdkafka client (C implementation) loggly: Using Loggly logmatic: Using mongodb(): Storing messages in a MongoDB database mqtt() destination: sending messages from a local network to an MQTT broker 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 Sumo Logic destinations: sumologic-http() and sumologic-syslog() 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
Parsing syslog messages Parsing messages with comma-separated and similar values Parsing key=value pairs JSON parser XML parser Parsing dates and timestamps Python parser Parsing tags Apache access log parser Linux audit parser Cisco parser Parsing enterprise-wide message model (EWMM) messages iptables parser Netskope parser panos-parser(): parsing PAN-OS log messages Sudo parser MariaDB parser Websense parser Fortigate parser Check Point Log Exporter parser Regular expression (regexp) parser 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

usertty: Sending messages to a user terminal: usertty() destination

This driver writes messages to the terminal of a logged-in user.

The usertty() driver has a single required argument, specifying a username who should receive a copy of matching messages. Use the asterisk * to specify every user currently logged in to the system.


The usertty() does not have any further options nor does it support templates.

Example: Using the usertty() driver
destination d_usertty { usertty("root"); };
Accepted values: number [seconds]
Default: 60

Description: The time to wait in seconds before a dead connection is reestablished.

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Write your own custom destination in Java or Python

The syslog-ng OSE application is open source, so if you have the necessary programming skills, you can extend it if its features are not adequate for your particular environment or needs. You can write destinations and other extensions to syslog-ng OSE in C (the main language of syslog-ng OSE), or using its language bindings, for example, Java or Python. .

NOTE: If you delete all Java destinations from your configuration and reload syslog-ng, the JVM is not used anymore, but it is still running. If you want to stop JVM, stop syslog-ng and then start syslog-ng again.

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Client-side failover

syslog-ng OSE can detect if the remote server of a network destination becomes inaccessible, and start sending messages to a secondary server. You can configure multiple failover servers, so if the secondary server becomes inaccessible as well, syslog-ng OSE switches to the third server in the list, and so on. If there are no more failover servers left, syslog-ng OSE returns to the beginning of a list and attempts to connect to the primary server.

The primary server is the address you provided in the destination driver configuration and it has a special role. syslog-ng OSE nominates this destination over the failover servers, and handles it as the primary address.

When syslog-ng OSE starts up, it always connects to the primary server first. In the failover() option there is a possibility to customize the failover modes.

Depending on how you set the failback() option, syslog-ng OSE behaves as follows:

  • round-robin mode: If failback() is not set, syslog-ng OSE does not attempt to return to the primary server even if it becomes available. In case the failover server fails, syslog-ng OSE attempts to connect the next failover server in the list in round-robin fashion.

    Example: round-robin mode

    In the following example syslog-ng OSE handles the logservers in round-robin fashion if the primary logserver becomes inaccessible (therefore failback() option is not set).

    destination d_network {
              failover( servers("failover-server1", "failover-server2") )
  • failback mode: If failback() is set, syslog-ng OSE attempts to return to the primary server.

    After syslog-ng OSE connects a secondary server during a failover, it sends a probe every tcp-probe-interval() seconds towards the primary server. If the primary logserver responds with a TCP ACK packet, the probe is successful. When the number of successful probes reaches the value set in the successful-probes-required() option, syslog-ng OSE tries to connect the primary server using the last probe.

    NOTE: syslog-ng OSE always waits for the result of the last probe before sending the next message. So if one connection attempt takes longer than the configured interval, that is, it waits for connection time out, you may experience longer intervals between actual probes.

    Example: failback mode

    In the following example syslog-ng OSE attempts to return to the primary logserver, as set in the failback() option: it will check if the server is accessible every tcp-probe-interval() seconds, and reconnect to the primary logserver after three successful connection attempts.

    destination d_network_2 {
    		servers("failover-server1", "failover-server2")

If syslog-ng OSE is restarted, it attempts to connect the primary server.

If syslog-ng OSE uses TLS-encryption to communicate with the remote server, syslog-ng OSE checks the certificate of the failover server as well. The certificates of the failover servers should match their domain names or IP addresses — for details, see Encrypting log messages with TLS. Note that when mutual authentication is used, the syslog-ng OSE client sends the same certificate to every server.

The primary server and the failover servers must be accessible with the same communication method: it is not possible to use different destination drivers or options for the different servers.

NOTE: Client-side failover works only for TCP-based connections (including TLS-encrypted connections), that is, the syslog() and network() destination drivers (excluding UDP transport).

Client-side failover is not supported in the sql() driver, even though it may use a TCP connection to access a remote database.

For details on configuring failover servers, see network() destination options and syslog() destination options.

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log: Filter and route log messages using log paths, flags, and filters

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