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syslog-ng Premium Edition 7.0.24 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng PE 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 google-pubsub: collecting messages from the Google Pub/Sub messaging service wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs mssql, oracle, sql: collecting messages from an SQL database network: Collecting messages using the RFC3164 protocol (network() driver) office365: Fetching logs from Office 365 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 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 udp-balancer: Receiving UDP messages at very high rate 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 google_pubsub: Sending logs to the Google Cloud Pub/Sub messaging service 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 sentinel: Sending logs to the Microsoft Azure Sentinel cloud snmp: Sending SNMP traps smtp: Generating SMTP messages (email) 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 Glossary

Licensing model and modes of operation

A Log Source Host (LSH) is any host, server, or device (including virtual machines, active or passive networking devices, syslog-ng clients and relays, and so on) that is capable of sending log messages. Log Source Hosts are identified by their IP addresses, so virtual machines and vhosts are separately counted.

The syslog-ng Premium Edition application has three distinct modes of operation: Client, Relay, and Server.

  • In Client mode syslog-ng Premium Edition collects local logs generated by the host it is running on, and forwards them through a network connection to the central syslog-ng PE server, a relay, or another network destination. If you install the syslog-ng Premium Edition application in Client mode on a host, it counts as a Log Source Host, even if it does not send log messages to a syslog-ng Premium Edition server.

  • In Relay mode syslog-ng Premium Edition receives logs through the network from Log Source Hosts and forwards them to the central syslog-ng PE server, a relay, or another network destination. If you install the syslog-ng Premium Edition application in Relay mode on a host, it counts as a Log Source Host, even if it does not send log messages to a syslog-ng Premium Edition server.

    Relays cannot store the received log messages in local files, except for the log messages of the relay host. Naturally, relays can use the disk-buffer option for every message.

  • In Server mode syslog-ng Premium Edition acts as a central log-collecting server that receives messages through a network connection, and stores them locally, or forwards them to other destinations or external systems (for example, a SIEM or a database). Installing the syslog-ng Premium Edition application in Server mode requires a license file, this license file determines the number of Log Source Hosts that can send log messages to the syslog-ng Premium Edition server.

Modes of operation in syslog-ng PE

Client mode Relay mode Server mode
Collect the local logs of the host ✔ ✔ ✔
Forward local logs over the network ✔ ✔ ✔
Store local messages in local files ✔ ✔ ✔
Receive logs over the network no ✔ ✔
Forward received logs over the network no ✔ ✔
Store received logs in local files no no ✔
Forward logs using special destinations (for example, databases) no no ✔
Requires license file no no ✔
Notes about counting the licensed hosts

Note that the number of source hosts is important, not the number of hosts that directly sends messages to syslog-ng Premium Edition: every host that send messages to the server (directly or using a relay) counts as a Log Source Host.

  • If the actual IP address of the host differs from the IP address received by looking up its IP address from its hostname in the DNS, the syslog-ng server counts them as two different hosts.

  • The chain-hostnames() option of syslog-ng can interfere with the way syslog-ng PE counts the log source hosts, causing syslog-ng to think there are more hosts logging to the central server, especially if the clients sends a hostname in the message that is different from its real hostname (as resolved from DNS). Disable the chain-hostnames() option on your log sources to avoid any problems related to license counting.

  • If the number of Log Source Hosts reaches the license limit, the syslog-ng PE server will not accept connections from additional hosts. The messages sent by additional hosts will be dropped, even if the client uses a reliable transport method (for example, ALTP).

    To make syslog-ng PE forget old clients that do not exist anymore, enable the reset-license-counter() global option.

  • If the no-parse flag is set in a message source on the syslog-ng PE server, syslog-ng PE assumes that the message arrived from the host (that is, from the last hop) that sent the message to syslog-ng PE, and information about the original sender is lost.

GPL and LGPL licenses

Starting with version 4 F1, the syslog-ng Premium Edition application is based on the syslog-ng Open Source Edition application, and includes elements that are licensed under the LGPL or GPL licenses. You can download the core of syslog-ng PE here. The components located under the /lib directory are licensed under the GNU Lesser General Public License Version 2.1 license, while the rest of the codebase is licensed under the GNU General Public License Version 2 license. External libraries and other dependencies used by syslog-ng PE have their own licenses, typically GPL, LGPL, MIT, or BSD.

Third-party contributions includes the text of the licenses applicable to syslog-ng Premium Edition.

High availability support

Multiple syslog-ng servers can be run in fail-over mode. The syslog-ng application does not include any internal support for this, as clustering support must be implemented on the operating system level. A tool that can be used to create UNIX clusters is Heartbeat (for details, see this page).

One Identity also has a log server appliance called syslog-ng Store Box that supports high-availability. For details, see the syslog-ng Store Box Product Page.

The structure of a log message

The following sections describe the structure of log messages. Currently there are two standard syslog message formats:

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