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syslog-ng Open Source Edition 3.36 - 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 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 Logmatic.io 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 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

syslog() source options

The syslog() driver has the following options.

ca-dir()
Accepted values: Directory name
Default: none

Description: The name of a directory that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject's name. This naming can be created using the c_rehash utility in openssl. For an example, see Configuring TLS on the syslog-ng clients. The syslog-ng OSE application uses the CA certificates in this directory to validate the certificate of the peer.

This option can be used together with the optional ca-file() option.

ca-file()
Accepted values: File name
Default: empty

Description: Optional. The name of a file that contains a set of trusted CA certificates in PEM format. The syslog-ng OSE application uses the CA certificates in this file to validate the certificate of the peer.

Example format in configuration:

ca-file("/etc/pki/tls/certs/ca-bundle.crt")

NOTE: The ca-file() option can be used together with the ca-dir() option, and it is relevant when peer-verify() is set to other than no or optional-untrusted.

dynamic-window-size()
Type: number
Default: 0

Description: The size of the dynamic control window used during flow-control. For details on flow-control, see Managing incoming and outgoing messages with flow-control.

encoding()
Type: string
Default:

Description: Specifies the character set (encoding, for example, UTF-8) of messages using the legacy BSD-syslog protocol. To list the available character sets on a host, execute the iconv -l command. For details on how encoding affects the size of the message, see Message size and encoding.

flags()
Type: assume-utf8, empty-lines, expect-hostname, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, store-raw-message, syslog-protocol, validate-utf8
Default: empty set

Description: Specifies the log parsing options of the source.

  • assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.

  • empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng OSE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng OSE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.

  • guess-timezone: Attempt to guess the timezone of the message if this information is not available in the message. Works when the incoming message stream is close to real time, and the timezone information is missing from the timestamp.

  • kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

  • no-header: The no-header flag triggers syslog-ng OSE to parse only the PRI field of incoming messages, and put the rest of the message contents into $MSG.

    Its functionality is similar to that of the no-parse flag, except the no-header flag does not skip the PRI field.

    NOTE: Essentially, the no-header flag signals syslog-ng OSE that the syslog header is not present (or does not adhere to the conventions / RFCs), so the entire message (except from the PRI field) is put into $MSG.

    Example: using the no-header flag with the syslog-parser() parser

    The following example illustrates using the no-header flag with the syslog-parser() parser:

    parser p_syslog {
      syslog-parser(
        flags(no-header)
      );
    };
  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng OSE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:

    source s_dell {
        network(
            port(2000)
            flags(no-hostname)
        );
    };
  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the file() and pipe() drivers support multi-line messages.

  • no-parse: By default, syslog-ng OSE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng OSE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MESSAGE part of the syslog message (available using the ${MESSAGE} macro). This flag is useful for parsing messages not complying to the syslog format.

    If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng OSE generates a new syslog header (timestamp, host, and so on) automatically. Note that even though flags(no-parse) disables message parsing, some flags can still be used, for example, the no-multi-line flag.

  • dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful if the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.

  • sanitize-utf8: When using the sanitize-utf8 flag, syslog-ng OSE converts non-UTF-8 input to an escaped form, which is valid UTF-8.

  • store-raw-message: Save the original message as received from the client in the ${RAWMSG} macro. You can forward this raw message in its original form to another syslog-ng node using the syslog-ng() destination, or to a SIEM system, ensuring that the SIEM can process it. Available only in 3.16 and later.

  • syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

  • validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see IETF-syslog messages). If the BOM1 character is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.

  • threaded: The threaded flag enables multithreading for the source. For details on multithreading, see Multithreading and scaling in syslog-ng OSE.

    NOTE: The syslog source uses multiple threads only if the source uses the tls or tcp transport protocols.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};
host-override()
Type: string
Default:

Description: Replaces the ${HOST} part of the message with the parameter string.

interface()
Type: string
Default: None

Description: Bind to the specified interface instead of an IP address. Available in 3.19 and later.

ip() or localip()
Type: string
Default: 0.0.0.0

Description: The IP address to bind to. By default, syslog-ng OSE listens on every available interface. Note that this is not the address where messages are accepted from.

If you specify a multicast bind address and use the udp transport, syslog-ng OSE automatically joins the necessary multicast group. TCP does not support multicasting.

ip-protocol()
Type: number
Default: 4

Description: Determines the internet protocol version of the given driver (network() or syslog()). The possible values are 4 and 6, corresponding to IPv4 and IPv6. The default value is ip-protocol(4).

Note that listening on a port using IPv6 automatically means that you are also listening on that port using IPv4. That is, if you want to have receive messages on an IP-address/port pair using both IPv4 and IPv6, create a source that uses the ip-protocol(6). You cannot have two sources with the same IP-address/port pair, but with different ip-protocol() settings (it causes an Address already in use error).

For example, the following source receives messages on TCP, using the network() driver, on every available interface of the host on both IPv4 and IPv6.

source s_network_tcp { network( transport("tcp") ip("::") ip-protocol(6) port(601) ); };
ip-tos()
Type: number
Default: 0

Description: Specifies the Type-of-Service value of outgoing packets.

ip-ttl()
Type: number
Default: 0

Description: Specifies the Time-To-Live value of outgoing packets.

keep-alive()
Type: yes or no
Default: yes

Description: Specifies whether connections to sources should be closed when syslog-ng is forced to reload its configuration (upon the receipt of a SIGHUP signal). Note that this applies to the server (source) side of the syslog-ng connections, client-side (destination) connections are always reopened after receiving a HUP signal unless the keep-alive option is enabled for the destination.

keep-hostname()
Type: yes or no
Default: no

Description: Enable or disable hostname rewriting.

  • If enabled (keep-hostname(yes)), syslog-ng OSE assumes that the incoming log message was sent by the host specified in the HOST field of the message.

  • If disabled (keep-hostname(no)), syslog-ng OSE rewrites the HOST field of the message, either to the IP address (if the use-dns() parameter is set to no), or to the hostname (if the use-dns() parameter is set to yes and the IP address can be resolved to a hostname) of the host sending the message to syslog-ng OSE. For details on using name resolution in syslog-ng OSE, see Using name resolution in syslog-ng.

    s

NOTE: If the log message does not contain a hostname in its HOST field, syslog-ng OSE automatically adds a hostname to the message.

  • For messages received from the network, this hostname is the address of the host that sent the message (this means the address of the last hop if the message was transferred via a relay).

  • For messages received from the local host, syslog-ng OSE adds the name of the host.

This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

NOTE: When relaying messages, enable this option on the syslog-ng OSE server and also on every relay, otherwise syslog-ng OSE will treat incoming messages as if they were sent by the last relay.

keep-timestamp()
Type: yes or no
Default: yes

Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

Caution:

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng OSE).

listen-backlog()
Type: integer
Default: 256

Description: Available only for stream based transports (unix-stream, tcp, tls). In TCP, connections are treated incomplete until the three-way handshake is completed between the server and the client. Incomplete connection requests wait on the TCP port for the listener to accept the request. The listen-backlog() option sets the maximum number of incomplete connection requests. For example:

source s_network {
    network(
        ip("192.168.1.1")
        transport("tcp")
        listen-backlog(2048)
        );
};
log-fetch-limit()
Type: number
Default: 100

Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.

log-iw-size()
Type: number
Default: 100

Description: The size of the initial window, this value is used during flow-control. Its value cannot be lower than 100, unless the dynamic-window-size() option is enabled. For details on flow-control, see Managing incoming and outgoing messages with flow-control.

If the max-connections() option is set, the log-iw-size() will be divided by the number of connections, otherwise log-iw-size() is divided by 10 (the default value of the max-connections() option). The resulting number is the initial window size of each connection. For optimal performance when receiving messages from syslog-ng OSE clients, make sure that the window size is larger than the flush-lines() option set in the destination of your clients.

Example: Initial window size of a connection

If log-iw-size(1000) and max-connections(10), then each connection will have an initial window size of 100.

log-msg-size()
Type: number (bytes)
Default: Use the global log-msg-size() option, which defaults to 65536 (64 KiB).

Description: Maximum length of an incoming message in bytes. This length includes the entire message (the data structure and individual fields). The maximal value that can be set is 268435456 bytes (256 MiB).

For messages using the IETF-syslog message format (RFC5424), the maximal size of the value of an SDATA field is 64 KiB.

NOTE: In most cases, log-msg-size() does not need to be set higher than 10 MiB.

For details on how encoding affects the size of the message, see Message size and encoding.

You can use human-readable units when setting configuration options. For details, seeNotes about the configuration syntax.

Uses the value of the global option if not specified.

max-connections()
Type: number
Default: 10

Description: Specifies the maximum number of simultaneous connections.

pad-size()
Type: number
Default: 0

Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. The syslog-ng OSE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:

Padding was set, and couldn't read enough bytes
port() or localport()
Type: number
Default:

In case of TCP transport: 514

In case of UDP transport: 514

Description: The port number to bind to.

program-override()
Type: string
Default:

Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.

so-broadcast()
Type: yes or no
Default: no

Description: This option controls the SO_BROADCAST socket option required to make syslog-ng send messages to a broadcast address. For details, see the socket(7) manual page.

so-keepalive()
Type: yes or no
Default: no

Description: Enables keep-alive messages, keeping the socket open. This only effects TCP and UNIX-stream sockets. For details, see the socket(7) manual page.

so-rcvbuf()
Type: number
Default: 0

Description: Specifies the size of the socket receive buffer in bytes. For details, see the socket(7) manual page.

Caution:

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng OSE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In this cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

so-reuseport()
Type: yes or no
Default: no

Description: Enables SO_REUSEPORT on systems that support it. When enabled, the kernel allows multiple UDP sockets to be bound to the same port, and the kernel load-balances incoming UDP datagrams to the sockets. The sockets are distributed based on the hash of (srcip, dstip, srcport, dstport), so the same listener should be receiving packets from the same endpoint. For example:

source {
        udp(so-reuseport(1) port(2000) persist-name("udp1"));
        udp(so-reuseport(1) port(2000) persist-name("udp2"));
        udp(so-reuseport(1) port(2000) persist-name("udp3"));
        udp(so-reuseport(1) port(2000) persist-name("udp4"));
};

Enables keep-alive messages, keeping the socket open. This only effects TCP and UNIX-stream sockets. For details, see the socket(7) manual page.

so-sndbuf()
Type: number
Default: 0

Description: Specifies the size of the socket send buffer in bytes. For details, see the socket(7) manual page.

tags()
Type: string
Default:

Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example, tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.

time-zone()
Type: name of the timezone, or the timezone offset
Default:

Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.

The timezone can be specified by using the name, for example, time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format, for example, +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

transport()
Type: udp, tcp, tls, proxied-tcp, proxied-tls, proxied-tls-passthrough, text-with-nuls
Default: tcp

Description: Specifies the protocol used to receive messages from the source.

For detailed information about how syslog-ng OSE supports the proxied-tcp, the proxied-tls, and the proxied-tls-passthrough parameters, see Proxy Protocol support.

text-with-nuls: Allows embedded NUL characters in the message from a TCP source, that is, syslog-ng OSE will not delimiter the incoming messages on NUL characters, only on newline characters (contrary to tcp transport, which splits the incoming log on newline characters and NUL characters).

NOTE: The syslog-ng OSE application does not support embedded NUL characters everywhere, so it is recommended that you also use flags(no-multi-line) that causes NUL characters to be replaced by space.

Caution:

When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the syslog-ng OSE server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the so-rcvbuf() option of the source is increased. In this cases, you will need to increase the net.core.rmem_max parameter of the host (for example, to 1024000), but do not modify net.core.rmem_default parameter.

As a general rule, increase the so-rcvbuf() so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the so-rcvbuf() at least to 2 097 152 bytes.

trim-large-messages()
Type: yes|no
Default: Use the global trim-large-messages() option, which defaults to no.

Description: Determines what syslog-ng OSE does with incoming log messages that are received using the IETF-syslog protocol using the syslog() driver, and are longer than the value of log-msg-size(). Other drivers ignore the trim-large-messages() option.

  • If set to no, syslog-ng OSE drops the incoming log message.

  • If set to yes, syslog-ng OSE trims the incoming log message to the size set in log-msg-size(), and adds the trimmed tag to the message. The rest of the message is dropped. You can use the tag to filter on such messages.

    filter f_trimmed {
        tags("trimmed");
    };

    If syslog-ng OSE trims a log message, it sends a debug-level log message to its internal() source.

    As a result of trimming, a parser could fail to parse the trimmed message. For example, a trimmed JSON or XML message will not be valid JSON or XML.

Available in syslog-ng OSE version 3.21 and later.

Uses the value of the global option if not specified.

tls()
Type: tls options
Default: n/a

Description: This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see TLS options.

use-dns()
Type: yes, no, persist_only
Default: yes

Description: Enable or disable DNS usage. The persist_only option attempts to resolve hostnames locally from file (for example, from /etc/hosts). The syslog-ng OSE application blocks on DNS queries, so enabling DNS may lead to a Denial of Service attack. To prevent DoS, protect your syslog-ng network endpoint with firewall rules, and make sure that all hosts which may get to syslog-ng are resolvable. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

NOTE: This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

use-fqdn()
Type: yes or no
Default: no

Description: Use this option to add a Fully Qualified Domain Name (FQDN) instead of a short hostname. You can specify this option either globally or per-source. The local setting of the source overrides the global option if available.

TIP: Set use-fqdn() to yes if you want to use the custom-domain() global option.

NOTE: This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

system: Collecting the system-specific log messages of a platform

Starting with version 3.2, syslog-ng OSE can automatically collect the system-specific log messages of the host on a number of platforms using the system() driver. If the system() driver is included in the syslog-ng OSE configuration file, syslog-ng OSE automatically adds the following sources to the syslog-ng OSE configuration.

NOTE:syslog-ng OSE versions 3.2-3.3 used an external script to generate the system() source, but this was problematic in certain situations, for example, when the host used a strict AppArmor profile. Therefore, the system() source is now generated internally in syslog-ng OSE.

The system() driver is also used in the default configuration file of syslog-ng OSE. For details on the default configuration file, see Example: The default configuration file of syslog-ng OSE. Starting with syslog-ng OSE version 3.6, you can use the system-expand command-line utility (which is a shell script, located in the modules/system-source/ directory) to display the configuration that the system() source will use.

Caution:

If syslog-ng OSE does not recognize the platform it is installed on, it does not add any sources.

Starting with version 3.6, syslog-ng OSE parses messages complying with the Splunk Common Information Model (CIM) and marked with @cim as JSON messages (for example, the ulogd from the netfilter project can emit such messages). That way, you can forward such messages without losing any information to CIM-aware applications (for example, Splunk).

Table 8: Sources automatically added by syslog-ng Open Source Edition
Platform Message source
AIX
unix-dgram("/dev/log");
FreeBSD
unix-dgram("/var/run/log");
unix-dgram("/var/run/logpriv" perm(0600));
file("/dev/klog" follow-freq(0) program-override("kernel") flags(no-parse));

For FreeBSD versions earlier than 9.1, follow-freq(1) is used.

GNU/kFreeBSD
unix-dgram("/var/run/log");
file("/dev/klog" follow-freq(0) program-override("kernel"));
HP-UX
pipe("/dev/log" pad-size(2048));
Linux
unix-dgram("/dev/log");
file("/proc/kmsg" program-override("kernel") flags(kernel));

Note that on Linux, the so-rcvbuf() option of the system() source is automatically set to 8192.

If the host is running under systemd, syslog-ng OSE reads directly from the systemd journal file using the systemd-journal() source.

If the kernel of the host is version 3.5 or newer, and /dev/kmsg is seekable, syslog-ng OSE will use that instead of /proc/kmsg, using the multi-line-mode(indented), keep-timestamp(no), and the format(linux-kmsg) options.

If syslog-ng OSE is running in a jail or a Linux Container (LXC), it will not read from the /dev/kmsg or /proc/kmsg files.

macOS
file("/var/log/system.log" follow-freq(1));

NOTE: Starting with version 3.7, the syslog-ng OSEsystem() driver automatically extracts the msgid from the message (if available), and stores it in the .solaris.msgid macro. To extract the msgid from the message without using the system()driver, use the extract-solaris-msgid() parser. You can find the exact source of this parser in the syslog-ng OSE GitHub repository.

NetBSD
unix-dgram("/var/run/log");

NOTE: Starting with version 3.7, the syslog-ng OSEsystem() driver automatically extracts the msgid from the message (if available), and stores it in the .solaris.msgid macro. To extract the msgid from the message without using the system()driver, use the extract-solaris-msgid() parser. You can find the exact source of this parser in the syslog-ng OSE GitHub repository.

Solaris 8
sun-streams("/dev/log");

NOTE: Starting with version 3.7, the syslog-ng OSEsystem() driver automatically extracts the msgid from the message (if available), and stores it in the .solaris.msgid macro. To extract the msgid from the message without using the system()driver, use the extract-solaris-msgid() parser. You can find the exact source of this parser in the syslog-ng OSE GitHub repository.

Solaris 9
sun-streams("/dev/log" door("/etc/.syslog_door"));

NOTE: Starting with version 3.7, the syslog-ng OSEsystem() driver automatically extracts the msgid from the message (if available), and stores it in the .solaris.msgid macro. To extract the msgid from the message without using the system()driver, use the extract-solaris-msgid() parser. You can find the exact source of this parser in the syslog-ng OSE GitHub repository.

Solaris 10
sun-streams("/dev/log" door("/var/run/syslog_door"));

NOTE: Starting with version 3.7, the syslog-ng OSEsystem() driver automatically extracts the msgid from the message (if available), and stores it in the .solaris.msgid macro. To extract the msgid from the message without using the system()driver, use the extract-solaris-msgid() parser. You can find the exact source of this parser in the syslog-ng OSE GitHub repository.

system() source options

The system() driver has the following options:

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type: string
Default: N/A

Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type: string
Default: N/A

Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

systemd-journal: Collecting messages from the systemd-journal system log storage

The systemd-journal() source is used on various Linux distributions, such as RHEL (from RHEL7) and CentOS. The systemd-journal() source driver can read the structured name-value format of the journald system service, making it easier to reach the custom fields in the message. By default, syslog-ng OSE adds the .journald. prefix to the name of every parsed value. For a list and description of name-value pairs that journald provides, see the documentation of journald for your platform (for example, man systemd.journal-fields).

The systemd-journal() source driver is designed to read only local messages through the systemd-journal API. It is not possible to set the location of the journal files, or the directories.

NOTE: The log-msg-size() option is not applicable for this source. Use the max-field-size() option instead.

NOTE: This source will not handle the following cases:

  • Corrupted journal file

  • Incorrect journal configuration

  • Any other journald-related bugs

NOTE: If you are using RHEL-7, the default source in the configuration is systemd-journal() instead of unix-dgram("/dev/log") and file("/proc/kmsg"). If you are using unix-dgram("/dev/log") or unix-stream("/dev/log") in your configuration as a source, syslog-ng OSE will revert to using systemd-journal() instead.

Caution:

Only one systemd-journal() source can be configured in the configuration file. If there is more than one systemd-journal() source configured, syslog-ng OSE will not start.

Declaration:
systemd-journal(options);
Example: Sending all fields through syslog protocol using the systemd-journal() driver

To send all fields through the syslog protocol, enter the prefix in the following format: ".SDATA.<name>".

@version: 3.36

source s_journald {
    systemd-journal(prefix(".SDATA.journald."));
};

destination d_network {
    syslog("server.host");
};

log {
    source(s_journald);
    destination(d_network);
};
Example: Filtering for a specific field using the systemd-journal() driver
@version: 3.36

source s_journald {
    systemd-journal(prefix(".SDATA.journald."));
};

filter f_uid {"${.SDATA.journald._UID}" eq "1000"};

destination d_network {
    syslog("server.host");
};

log {
    source(s_journald);
    filter(f_uid);
    destination(d_network);
};
Example: Sending all fields in value-pairs using the systemd-journal() driver
@version: 3.36

source s_local {
    systemd-journal(prefix("journald."));
};

destination d_network {
    network("server.host" template("$(format_json --scope rfc5424 --key journald.*)\n"));
};

log {
    source(s_local);
    destination(d_network);
};

The journal contains credential information about the process that sent the log message. The syslog-ng OSE application makes this information available in the following macros:

Table 9: Predefined macros
Journald field syslog-ng predefined macro
MESSAGE $MESSAGE
_HOSTNAME $HOST
_PID $PID
_COMM or SYSLOG_IDENTIFIER $PROGRAM If both _COMM and SYSLOG_IDENTIFIER exists, syslog-ng OSE uses SYSLOG_IDENTIFIER
SYSLOG_FACILITY $FACILITY_NUM
PRIORITY $LEVEL_NUM
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