syslog-ng Open Source Edition 3.25 - Administration Guide

Collects log messages from plain-text files, for example, from the logfiles of an Apache webserver. If you want to use wildcards in the filename, use the wildcard-file() source.

The syslog-ng application notices if a file is renamed or replaced with a new file, so it can correctly follow the file even if logrotation is used. When syslog-ng is restarted, it records the position of the last sent log message in the /opt/syslog-ng/var/syslog-ng.persist file, and continues to send messages from this position after the restart.

The file driver has a single required parameter specifying the file to open. If you want to use wildcards in the filename, use the wildcard-file() source. For the list of available optional parameters, see file() source options.

Declaration:

file("filename");

Example: Using the file() driver

source s_file {
    file("/var/log/messages");
};

Example: Tailing files

The following source checks the access.log file every second for new messages.

source s_tail {
    file("/var/log/apache/access.log" follow-freq(1) flags(no-parse));
};

NOTE:

If the message does not have a proper syslog header, syslog-ng treats messages received from files as sent by the kern facility. Use the default-facility() and default-priority() options in the source definition to assign a different facility if needed.

Notes on reading kernel messages

source: Read, receive, and collect log messages > file: Collecting messages from text files > Notes on reading kernel messages

Note the following points when reading kernel messages on various platforms.

The kernel usually sends log messages to a special file (/dev/kmsg on BSDs, /proc/kmsg on Linux). The file() driver reads log messages from such files. The syslog-ng application can periodically check the file for new log messages if the follow-freq() option is set.
On Linux, the klogd daemon can be used in addition to syslog-ng to read kernel messages and forward them to syslog-ng. klogd used to preprocess kernel messages to resolve symbols and so on, but as this is deprecated by ksymoops there is really no point in running both klogd and syslog-ng in parallel. Also note that running two processes reading /proc/kmsg at the same time might result in dead-locks.
When using syslog-ng to read messages from the /proc/kmsg file, syslog-ng automatically disables the follow-freq() parameter to avoid blocking the file.
To read the kernel messages on HP-UX platforms, use the following options in the source statement:
```
file("/dev/klog" program-override("kernel") flags(kernel) follow-freq(0));
```

file() source options

source: Read, receive, and collect log messages > file: Collecting messages from text files > file() source options

The file() driver has the following options:

default-facility()

Type:	facility string
Default:	kern

Description: This parameter assigns a facility value to the messages received from the file source if the message does not specify one.

default-priority()

Type:	priority string
Default:

Description: This parameter assigns an emergency level to the messages received from the file source if the message does not specify one. For example, default-priority(warning).

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-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 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 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.

follow-freq()

Type:	number
Default:	1

Description: Indicates that the source should be checked periodically. This is useful for files which always indicate readability, even though no new lines were appended. If this value is higher than zero, syslog-ng will not attempt to use poll() on the file, but checks whether the file changed every time the follow-freq() interval (in seconds) has elapsed. Floating-point numbers (for example, 1.5) can be used as well.

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")
        )
     );
};

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).

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:	10000

Description: The size of the initial window, this value is used during flow control. Make sure that log-iw-size() is larger than the value of log-fetch-limit().

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.

log-prefix() (DEPRECATED)

Type:	string
Default:

Description: A string added to the beginning of every log message. It can be used to add an arbitrary string to any log source, though it is most commonly used for adding kernel: to the kernel messages on Linux.

NOTE:

This option is deprecated. Use program-override() instead.

multi-line-garbage()

Type:	regular expression
Default:	empty string

Description: Use the multi-line-garbage() option when processing multi-line messages that contain unneeded parts between the messages. Specify a string or regular expression that matches the beginning of the unneeded message parts. If the multi-line-garbage() option is set, syslog-ng OSE ignores the lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix(). See also the multi-line-prefix() option.

When receiving multi-line messages from a source when the multi-line-garbage() option is set, but no matching line is received between two lines that match multi-line-prefix(), syslog-ng OSE will continue to process the incoming lines as a single message until a line matching multi-line-garbage() is received.

To use the multi-line-garbage() option, set the multi-line-mode() option to prefix-garbage.

Caution:

If the multi-line-garbage() option is set, syslog-ng OSE discards lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix().

multi-line-mode()

Type:	indented\|regexp
Default:	empty string

Description: Use the multi-line-mode() option when processing multi-line messages. The syslog-ng OSE application provides the following methods to process multi-line messages:

The indented mode can process messages where each line that belongs to the previous line is indented by whitespace, and the message continues until the first non-indented line. For example, the Linux kernel (starting with version 3.5) uses this format for /dev/log, as well as several applications, like Apache Tomcat.
Example: Processing indented multi-line messages
```
source s_tomcat {
    file("/var/log/tomcat/xxx.log" multi-line-mode(indented));
};
```
The prefix-garbage mode uses a string or regular expression (set in multi-line-prefix()) that matches the beginning of the log messages, ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. For details on using multi-line-mode(prefix-garbage), see the multi-line-prefix() and multi-line-garbage() options.
The prefix-suffix mode uses a string or regular expression (set in multi-line-prefix()) that matches the beginning of the log messages, ignores newline characters from the source until a line matches the regular expression set in multi-line-suffix(), and treats the lines between multi-line-prefix() and multi-line-suffix() as a single message. Any other lines between the end of the message and the beginning of a new message (that is, a line that matches the multi-line-prefix() expression) are discarded. For details on using multi-line-mode(prefix-suffix), see the multi-line-prefix() and multi-line-suffix() options.

The prefix-suffix mode is similar to the prefix-garbage mode, but it appends the garbage part to the message instead of discarding it.

TIP:

To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:
```
destination d_file {
    file ("/var/log/messages"
        template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n")
    );
};
```
For details on using templates, see Templates and macros.
To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.

multi-line-prefix()

Type:	regular expression starting with the ^ character
Default:	empty string

Description: Use the multi-line-prefix() option to process multi-line messages, that is, log messages that contain newline characters (for example, Tomcat logs). Specify a string or regular expression that matches the beginning of the log messages (always start with the ^ character). Use as simple regular expressions as possible, because complex regular expressions can severely reduce the rate of processing multi-line messages. If the multi-line-prefix() option is set, syslog-ng OSE ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. See also the multi-line-garbage() option.

TIP:

To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:
```
destination d_file {
    file ("/var/log/messages"
        template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n")
    );
};
```
For details on using templates, see Templates and macros.
To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.

Example: Processing Tomcat logs

The log messages of the Apache Tomcat server are a typical example for multi-line log messages. The messages start with the date and time of the query in the YYYY.MM.DD HH:MM:SS format, as you can see in the following example.

2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start:
LifecycleException:  service.getName(): "Catalina";  Protocol handler start failed: java.net.BindException: Address already in use null:8080
       at org.apache.catalina.connector.Connector.start(Connector.java:1138)
       at org.apache.catalina.core.StandardService.start(StandardService.java:531)
       at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
       at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
       at java.lang.reflect.Method.invoke(Method.java:597)
       at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177)
2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
INFO: Server startup in 1206 ms
2010.06.09. 12:45:08 org.apache.coyote.http11.Http11Protocol pause
INFO: Pausing Coyote HTTP/1.1 on http-8080
2010.06.09. 12:45:09 org.apache.catalina.core.StandardService stop
INFO: Stopping service Catalina

To process these messages, specify a regular expression matching the timestamp of the messages in the multi-line-prefix() option. Such an expression is the following:

source s_file{file("/var/log/tomcat6/catalina.2010-06-09.log" follow-freq(0) multi-line-mode(regexp) multi-line-prefix("[0-9]{4}\.[0-9]{2}\.[0-9]{2}\.") flags(no-parse));};
};

Note that flags(no-parse) is needed to prevent syslog-ng OSE trying to interpret the date in the message.

multi-line-suffix()

Type:	regular expression
Default:	empty string

Description: Use the multi-line-suffix() option when processing multi-line messages. Specify a string or regular expression that matches the end of the multi-line message.

To use the multi-line-suffix() option, set the multi-line-mode() option to prefix-suffix. See also the multi-line-prefix() option.

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

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.

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.

wildcard-file: Collecting messages from multiple text files

source: Read, receive, and collect log messages > wildcard-file: Collecting messages from multiple text files

The wildcard-file() source collects log messages from multiple plain-text files from multiple directories. The wildcard-file() source is available in syslog-ng OSE version 3.10 and later.

The syslog-ng OSE application notices if a file is renamed or replaced with a new file, so it can correctly follow the file even if logrotation is used. When syslog-ng OSE is restarted, it records the position of the last sent log message in the persist file, and continues to send messages from this position after the restart. The location of the persist file depends on the package you installed syslog-ng OSE from, typically it is /var/lib/syslog-ng/syslog-ng.persist or /opt/syslog-ng/var/syslog-ng.persist.

Declaration:

wildcard-file(
    base-dir("<pathname>")
    filename-pattern("<filename>")
);

Note the following important points:

You can use the * and ? wildcard characters in the filename (the filename-pattern() option), but not in the path (the base-dir() option).
If you use multiple wildcard-file() sources in your configuration, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss.
When using wildcards, syslog-ng OSE monitors every matching file (up to the limit set in the max-files() option), and can receive new log messages from any of the files. However, monitoring (polling) many files (that is, more than ten) has a significant overhead and may affect performance. On Linux this overhead is not so significant, because syslog-ng OSE uses the inotify feature of the kernel. Set the max-files() option at least to the number of files you want to monitor. If the wildcard-file source matches more files than the value of the max-files() option, it is random which files will syslog-ng OSE actually monitor. The default value of max-files() is 100.
If the message does not have a proper syslog header, syslog-ng OSE treats messages received from files as sent by the user facility. Use the default-facility() and default-priority() options in the source definition to assign a different facility if needed.
For every message that syslog-ng OSE reads from the source files, the path and name of the file is available in the ${FILE_NAME} macro.

Required parameters: base-dir(), filename-pattern(). For the list of available optional parameters, see wildcard-file() source options.

Example: Using the wildcard-file() driver

The following example monitors every file with the .log extension in the /var/log directory for log messages.

source s_files {
    wildcard-file(
        base-dir("/var/log")
        filename-pattern("*.log")
        recursive(no)
        follow-freq(1)
    );
};

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syslog-ng Open Source Edition 3.25 - Administration Guide

file: Collecting messages from text files

Declaration:

Example: Using the file() driver

Example: Tailing files

Notes on reading kernel messages

file() source options

default-facility()

default-priority()

encoding()

flags()

follow-freq()

hook-commands()

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

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

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

keep-timestamp()

log-fetch-limit()

log-iw-size()

log-msg-size()

log-prefix() (DEPRECATED)

multi-line-garbage()

multi-line-mode()

Example: Processing indented multi-line messages

multi-line-prefix()

Example: Processing Tomcat logs

multi-line-suffix()

pad-size()

program-override()

tags()

time-zone()

wildcard-file: Collecting messages from multiple text files

Declaration:

Example: Using the wildcard-file() driver

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