syslog-ng Open Source Edition 3.25 - Administration Guide

bad-hostname()

Description: A regexp containing hostnames which should not be handled as hostnames.

chain-hostnames()

Description: Enable or disable the chained hostname format. If a client sends the log message directly to the syslog-ng OSE server, the chain-hostnames() option is enabled on the server, and the client sends a hostname in the message that is different from its DNS hostname (as resolved from DNS by the syslog-ng OSE server), then the server can append the resolved hostname to the hostname in the message (separated with a / character) when the message is written to the destination.

For example, consider a client-server scenario with the following hostnames: client-hostname-from-the-message, client-hostname-resolved-on-the-server, server-hostname. The hostname of the log message written to the destination depends on the keep-hostname() and the chain-hostnames() options. How keep-hostname() and chain-hostnames() options are related is described in the following table.

If the log message is forwarded to the syslog-ng OSE server via a syslog-ng OSE relay, the hostname depends on the settings of the keep-hostname() and the chain-hostnames() options both on the syslog-ng OSE relay and the syslog-ng OSE server.

For example, consider a client-relay-server scenario with the following hostnames: client-hostname-from-the-message, client-hostname-resolved-on-the-relay, client-hostname-resolved-on-the-server, relay-hostname-resolved-on-the-server. How keep-hostname() and chain-hostnames() options are related is described in the following table.

check-hostname()

Description: Enable or disable checking whether the hostname contains valid characters.

create-dirs()

Description: Enable or disable directory creation for destination files and sockets.

dir-group()

Description: The default group for newly created directories.

dir-owner()

Description: The default owner of newly created directories.

dir-perm()

Description: The permission mask of directories created by syslog-ng. Log directories are only created if a file after macro expansion refers to a non-existing directory, and directory creation is enabled (see also the create-dirs() option). For octal numbers prefix the number with 0, for example, use 0755 for rwxr-xr-x.

To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-perm(). Note that when creating a new directory without specifying attributes for dir-perm(), the default permission of the directories is masked with the umask of the parent process (typically 0022).

Starting with version 3.16, the default value of this option is -1, so syslog-ng OSE does not change the ownership, unless explicitly configured to do so.

dns-cache()

Description: Enable or disable DNS cache usage.

dns-cache-expire()

Description: Number of seconds while a successful lookup is cached.

dns-cache-expire-failed()

Description: Number of seconds while a failed lookup is cached.

dns-cache-hosts()

Description: Name of a file in /etc/hosts format that contains static IP->hostname mappings. Use this option to resolve hostnames locally without using a DNS. Note that any change to this file triggers a reload in syslog-ng and is instantaneous.

dns-cache-size()

Description: Number of hostnames in the DNS cache.

file-template()

Description: Specifies a template that file-like destinations use by default. For example:

template t_isostamp { template("$ISODATE $HOST $MSGHDR$MSG\n"); };

options { file-template(t_isostamp); };

flush-lines()

Description: Specifies how many lines are flushed to a destination at a time. The syslog-ng OSE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.

The syslog-ng OSE application flushes the messages if it has sent flush-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng OSE or in case of network sources, the connection with the client is closed, syslog-ng OSE automatically sends the unsent messages to the destination.

group()

Description: The default group of output files. By default, syslog-ng changes the privileges of accessed files (for example, /dev/null) to root.root 0600. To disable modifying privileges, use this option with the -1 value.

jvm-options()

Description: Specify the Java Virtual Machine (JVM) settings of your Java destination from the syslog-ng OSE configuration file.

For example:

jvm-options("-Xss1M -XX:+TraceClassLoading")

log-fifo-size()

Description: The number of messages that the output queue can store.

log-msg-size()

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.

mark() (DEPRECATED)

Description: The mark-freq() option is an alias for the deprecated mark() option. This is retained for compatibility with syslog-ng version 1.6.x.

on-error()

Description: Controls what happens when type-casting fails and syslog-ng OSE cannot convert some data to the specified type. By default, syslog-ng OSE drops the entire message and logs the error. Currently the value-pairs() option uses the settings of on-error().

• drop-message: Drop the entire message and log an error message to the internal() source. This is the default behavior of syslog-ng OSE.

• drop-property: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the internal() source.

• fallback-to-string: Convert the property to string and log an error message to the internal() source.

• silently-drop-message: Drop the entire message silently, without logging the error.

• silently-drop-property: Omit the affected property (macro, template, or message-field) silently, without logging the error.

• silently-fallback-to-string: Convert the property to string silently, without logging the error.

owner()

Description: The default owner of output files. If set, syslog-ng changes the owner of accessed files (for example, /dev/null) to this value, and the permissions to the value set in the perm() option.

Starting with version 3.16, the default value of this option is -1, so syslog-ng OSE does not change the ownership, unless explicitly configured to do so.

pass-unix-credentials()

Description: Enable syslog-ng OSE to collect UNIX credential information (that is, the PID, user ID, and group of the sender process) for messages received using UNIX domain sockets. Available only in syslog-ng Open Source Edition 3.7 and later. Note that collecting UNIX credential information from sockets in high-traffic environments can be resource intensive, therefore pass-unix-credentials() can be disabled globally, or separately for each source.

perm()

Description: The default permission for output files. If set, syslog-ng changes the permissions of accessed files (for example, /dev/null) to this value, and the onwer to the value set in the owner() option.

Starting with version 3.16, the default value of this option is -1, so syslog-ng OSE does not change the permissions, unless explicitly configured to do so.

proto-template()

Description: Specifies a template that protocol-like destinations (for example, network() and syslog()) use by default. For example:

template t_isostamp { template("$ISODATE $HOST $MSGHDR$MSG\n"); };

options { proto-template(t_isostamp); };

recv-time-zone()

Description: Specifies the time zone associated with the incoming messages, if not specified otherwise in the message or in the source driver. For details, see also Timezones and daylight saving and A note on timezones and timestamps.

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.

send-time-zone()

Description: Specifies the time zone associated with the messages sent by syslog-ng, if not specified otherwise in the message or in the destination driver. For details, see Timezones and daylight saving.

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.

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.

stats-freq()

Description: The period between two STATS messages in seconds. STATS are log messages sent by syslog-ng, containing statistics about dropped log messages. Set to 0 to disable the STATS messages.

stats-level()

Description: Specifies the detail of statistics syslog-ng collects about the processed messages.

• Level 0 collects only statistics about the sources and destinations.

• Level 1 contains details about the different connections and log files, but has a slight memory overhead.

• Level 2 contains detailed statistics based on the hostname.

• Level 3 contains detailed statistics based on various message parameters like facility, severity, or tags.

Note that level 2 and 3 increase the memory requirements and CPU load. For details on message statistics, see Statistics of syslog-ng.

stats-max-dynamics()

Description: To avoid performance issues or even overloading syslog-ng OSE (for example, if a script starts to send logs from different IP addresses to syslog-ng OSE), you might want to limit the number of registered dynamic counters in the message statistics. For details on message statistics, see Statistics of syslog-ng.

• Unlimited dynamic counters:

  If you do not use this option, dynamic counters will not be limited. This can be useful in cases where you are extremely interested in dynamic counters, and use these statistics extensively.

  Caution: In some cases, there might be even millions of dynamic counters

• Limited dynamic counter clusters:

  To limit dynamic counters, enter a number, and only a maximum of <number> counters will be registered in the statistics.

  In practice, this means dynamic counter clusters. A program name produces one dynamic counter cluster, that can include several counters, such as processed, stamp, and so on.

  Example: Limiting dynamic counter clusters 1

  If you set stats-max-dynamics() to 1, and 2 programs send messages, only one of these programs will be tracked in the dynamic counters, but it will have more than one counters.

  Example: Limiting dynamic counter clusters 2

  If you have 500 clients, and set stats-max-dynamics() to 1000, you will have enough number of counters reserved for these clients, but at the same time, you limit the use of your resources and therefore protect your system from being overloaded.

• No dynamic counters:

  To disable dynamic counters completely, set the value of this option to 0. This is the recommended value if you do not use statistics, or if you are not interested in dynamic counters in particular (for example, the number of logs arriving from programs).

sync() or sync-freq() (DEPRECATED)

Description: Obsolete aliases for flush-lines()

threaded()

Description: Enable syslog-ng OSE to run in multithreaded mode and use multiple CPUs. Available only in syslog-ng Open Source Edition 3.3 and later. Note that setting threaded(no) does not mean that syslog-ng OSE will use only a single thread. For details, see Multithreading and scaling in syslog-ng OSE.

time-reap()

Description: The time to wait in seconds before an idle destination file or pipe is closed. Note that only destination files having macros in their filenames are closed automatically.

Starting with version 3.23, the way how time-reap() works is the following.

1. If the time-reap() option of the destination is set, that value is used, for example:

   destination d_fifo {
       pipe(
           "/tmp/test.fifo",
           time-reap(30)  # sets time-reap() for this destination only
       );
   };

2. If the time-reap() option of the destination is not set, and the destination does not use a template or macro in its filename or path, time-reap() is automatically set to 0. For example:

   destination d_fifo {
       pipe(
           "/tmp/test.fifo",
       );
   };

3. Otherwise, the value of the global time-reap() option is used, which defaults to 60 seconds.

time-sleep() (DEPRECATED)

Description: The time to wait in milliseconds between each invocation of the poll() iteration.

trim-large-messages()

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.

ts-format()

Description: Specifies the timestamp format used when syslog-ng itself formats a timestamp and nothing else specifies a format (for example: STAMP macros, internal messages, messages without original timestamps). For details, see also A note on timezones and timestamps.

By default, timestamps include only seconds. To include fractions of a second (for example, milliseconds) use the frac-digits() option. For details, see frac-digits().

use-rcptid()

Description: When the use-rcptid global option is set to yes, syslog-ng OSE automatically assigns a unique reception ID to every received message. You can access this ID and use it in templates via the ${RCPTID} macro. The reception ID is a monotonously increasing 48-bit integer number, that can never be zero (if the counter overflows, it restarts with 1).

use-uniqid()

Description: This option enables generating a globally unique ID. It is generated from the HOSTID and the RCPTID in the format of HOSTID@RCPTID. It has a fixed length: 16+@+8 characters. You can include the unique ID in the message by using the macro. For details, see UNIQID.

Enabling this option automatically generates the HOSTID. The HOSTID is a persistent, 32-bits-long cryptographically secure pseudo random number, that belongs to the host that the syslog-ng is running on. If the persist file is damaged, the HOSTID might change.

Enabling this option automatically enables the RCPTID functionality. For details, see RCPTID