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syslog-ng Premium Edition 7.0.12 - 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 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
elasticsearch: Sending messages directly to Elasticsearch version 1.x elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher 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 syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng: Forwarding messages and tags 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 About us

syslog: Collecting messages using the IETF syslog protocol (syslog() driver)

The syslog() driver can receive messages from the network using the standard IETF-syslog protocol (as described in RFC5424-26). UDP, TCP, and TLS-encrypted TCP can all be used to transport the messages.

NOTE:

The syslog() driver can also receive BSD-syslog-formatted messages (described in RFC 3164, see BSD-syslog or legacy-syslog messages) if they are sent using the IETF-syslog protocol.

In syslog-ng PE versions 3.1 and earlier, the syslog() driver could handle only messages in the IETF-syslog (RFC 5424-26) format.

For the list of available optional parameters, see syslog() source options.

Declaration:
syslog(ip() port() transport() options());
Example: Using the syslog() driver

TCP source listening on the localhost on port 1999.

source s_syslog {
    syslog(
        ip(127.0.0.1)
        port(1999)
        transport("tcp")
    );
};

UDP source with defaults.

source s_udp { syslog( transport("udp")); };

Encrypted source where the client is also authenticated. For details on the encryption settings, see TLS options.

source s_syslog_tls{
    syslog(
        ip(10.100.20.40)
        transport("tls")
        tls(
            peer-verify(required-trusted)
            ca-dir('/opt/syslog-ng/etc/syslog-ng/keys/ca.d/')
            key-file('/opt/syslog-ng/etc/syslog-ng/keys/server_privatekey.pem')
            cert-file('/opt/syslog-ng/etc/syslog-ng/keys/server_certificate.pem')
        )
    );
};

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 PE 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 such 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.

syslog() source options

The syslog() driver has the following options.

encoding()
Type: string
Default:

Description: Specifies the characterset (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 PE removes empty lines automatically.

  • expect-hostname: If the expect-hostname flag is enabled, syslog-ng PE 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.

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

  • no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng PE 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 PE 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 PE 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 PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

  • 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 PE 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 7.0.9 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 theBOM1character 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 PE.

    NOTE:

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

host-override()
Type: string
Default:

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

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

Description: The IP address to bind to. By default, syslog-ng PE 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 PE 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 PE 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 PE 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 PE. For details on using name resolution in syslog-ng PE, see Using name resolution in syslog-ng.

NOTE:

If the log message does not contain a hostname in its HOST field, syslog-ng PE 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 PE 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 PE server and also on every relay, otherwise syslog-ng PE 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 PE).

log-fetch-limit()
Type: number
Default: 10

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. 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 PE 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.

Description: Maximum length of a 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 (256MB). For messages using the IETF-syslog message format (RFC5424), the maximal size of the value of an SDATA field is 64kB.

In most cases, it is not recommended to set log-msg-size() higher than 10 MiB.

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

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 PE 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: 601

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 PE 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 such 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-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 as using the name of the (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:

altp, udp, tcp, or tls

Default: tcp

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

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 PE 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 such 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.

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 PE 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: Add Fully Qualified Domain Name instead of short hostname. 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.

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

Starting with version 4 F1, syslog-ng PE 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 PE configuration file, syslog-ng PE automatically adds the following sources to the syslog-ng PE configuration.

NOTE:

syslog-ng PE versions 4.1-5.0 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 PE.

The system() driver is also used in the default configuration file of syslog-ng PE. For details on the default configuration file, see Example: The default configuration file of syslog-ng PE. Starting with syslog-ng PE version , 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 PE does not recognize the platform it is installed on, it does not add any sources.

Starting with version 7.0, syslog-ng PE 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 10: Sources automatically added by syslog-ng Premium Edition
Platform Message source
AIX and Tru64
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 PE 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 PE 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 PE is running in a jail or a Linux Container (LXC), it will not read from the /dev/kmsg or /proc/kmsg files.

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

NOTE:

Starting with version 7.0.7, the syslog-ng PE system() 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.

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

NOTE:

Starting with version 7.0.7, the syslog-ng PE system() 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.

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

NOTE:

Starting with version 7.0.7, the syslog-ng PE system() 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.

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 PE adds the .journald. prefix to the name of every parsed value.

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 PE will revert to using systemd-journal() instead.

Caution:

Only one systemd-journal() source can be configured in the configuration file. If there are more than one systemd-journal() sources configured, syslog-ng PE 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: 7.0

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: 7.0

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: 7.0

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 PE application makes this information available in the following 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 PE uses SYSLOG_IDENTIFIER
SYSLOG_FACILITY $FACILITY_NUM
PRIORITY $LEVEL_NUM
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