This section describes how to start, stop and check the status of syslog-ng Open Source Edition (syslog-ng OSE) service on Linux.
To start syslog-ng OSE, execute the following command as root.
systemctl start syslog-ng
If the service starts successfully, no output will be displayed.
The following message indicates that syslog-ng OSE can not start (see Checking syslog-ng OSE status):
Job for syslog-ng.service failed because the control process exited with error code. See systemctl status syslog-ng.service and journalctl -xe for details.
To stop syslog-ng OSE
systemctl stop syslog-ng
Check the status of syslog-ng OSE service (see Checking syslog-ng OSE status).
To restart syslog-ng OSE, execute the following command as root.
systemctl restart syslog-ng
To reload the configuration file without restarting syslog-ng OSE, execute the following command as root.
systemctl reload syslog-ng
To check the following status-related components, observe the suggestions below.
Checking the status of syslog-ng OSE service
To check the status of syslog-ng OSE service
Execute the following command as root.
systemctl --no-pager status syslog-ng
Check the Active: field, which shows the status of syslog-ng OSE service. The following statuses are possible:
active (running) - syslog-ng OSE service is up and running
syslog-ng.service - System Logger Daemon Loaded: loaded (/lib/systemd/system/syslog-ng.service; enabled; vendor preset: enabled) Active: active (running) since Tue 2019-06-25 08:58:09 CEST; 5s ago Main PID: 6575 (syslog-ng) Tasks: 3 Memory: 13.3M CPU: 268ms CGroup: /system.slice/syslog-ng.service 6575 /opt/syslog-ng/libexec/syslog-ng -F --no-caps --enable-core
inactive (dead) - syslog-ng service is stopped
syslog-ng.service - System Logger Daemon Loaded: loaded (/lib/systemd/system/syslog-ng.service; enabled; vendor preset: enabled) Active: inactive (dead) since Tue 2019-06-25 09:14:16 CEST; 2min 18s ago Process: 6575 ExecStart=/opt/syslog-ng/sbin/syslog-ng -F --no-caps --enable-core $SYSLOGNG_OPTIONS (code=exited, status=0/SUCCESS) Main PID: 6575 (code=exited, status=0/SUCCESS) Status: "Shutting down... Tue Jun 25 09:14:16 2019" Jun 25 09:14:31 as-syslog-srv systemd: Stopped System Logger Daemon.
Checking the process of syslog-ng OSE
To check the process of syslog-ng OSE, execute one of the following commands.
ps u `pidof syslog-ng`
Expected output example:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND syslogng 6709 0.0 0.6 308680 13432 ? Ss 09:17 0:00 /opt/syslog-ng/libexec/syslog-ng -F --no-caps --enable-core
ps axu | grep syslog-ng | grep -v grep
Expected output example:
syslogng 6709 0.0 0.6 308680 13432 ? Ss 09:17 0:00 /opt/syslog-ng/libexec/syslog-ng -F --no-caps --enable-core
Checking the internal logs of syslog-ng OSE
The internal logs of syslog-ng OSE contains informal, warning and error messages.
By default, syslog-ng OSE log messages (generated on the internal() source) are written to /var/log/messages.
Check the internal logs of syslog-ng OSE for any issue.
Message processing
The syslog-ng OSE application collects statistics about the number of processed messages on the different sources and destinations.
Central statistics
To check the central statistics, execute the following command to see the number of received and queued (sent) messages by syslog-ng OSE.
watch "/opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^center"
The output will be updated in every 2 seconds.
If the numbers are changing, syslog-ng OSE is processing the messages.
Every 2.0s: /opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^center Tue Jun 25 10:33:25 2019 center;;queued;a;processed;112 center;;received;a;processed;28
Source statistics
To check the source statistics, execute the following command to see the number of received messages on the configured sources.
watch "/opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^source"
The output will be updated in every 2 seconds.
If the numbers are changing, syslog-ng OSE is receiving messages on the sources.
Every 2.0s: /opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^source Tue Jun 25 10:40:50 2019 source;s_null;;a;processed;0 source;s_net;;a;processed;0 source;s_local;;a;processed;90
Destination statistics
To check the source statistics, execute the following command to see the number of received messages on the configured sources.
watch "/opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^source"
The output will be updated in every 2 seconds.
If the numbers are changing, syslog-ng OSE is receiving messages on the sources.
Every 2.0s: /opt/syslog-ng/sbin/syslog-ng-ctl stats | grep ^destination Tue Jun 25 10:41:02 2019 destination;d_logserver2;;a;processed;90 destination;d_messages;;a;processed;180 destination;d_logserver;;a;processed;90 destination;d_null;;a;processed;0
NOTE:If you find error messages in the internal logs, messages are not processed by syslog-ng OSE or you encounter any issue, you have the following options:
Location of the syslog-ng configuration file
The configuration syntax in detail
Notes about the configuration syntax
Defining configuration objects inline
Using channels in configuration objects
Global and environmental variables
Managing complex syslog-ng configurations
To configure syslog-ng OSE, edit the syslog-ng.conf file with any regular text editor application.
Every syslog-ng configuration file must begin with a line containing the version information of syslog-ng. For syslog-ng version 3.25, this line looks like:
@version: 3.25
Versioning the configuration file was introduced in syslog-ng 3.0. If the configuration file does not contain the version information, syslog-ng assumes that the file is for syslog-ng version 2.x. In this case it interprets the configuration and sends warnings about the parts of the configuration that should be updated. Version 3.0 and later will correctly operate with configuration files of version 2.x, but the default values of certain parameters have changed since 3.0.
The following is a very simple configuration file for syslog-ng: it collects the internal messages of syslog-ng and the messages from /dev/log into the /var/log/messages_syslog-ng.log file.
@version: 3.25 source s_local { unix-dgram("/dev/log"); internal(); }; destination d_file { file("/var/log/messages_syslog-ng.log"); }; log { source(s_local); destination(d_file); };
As a syslog-ng user described on a mailing list:
Alan McKinnon The syslog-ng's config file format was written by programmers for programmers to be understood by programmers. That may not have been the stated intent, but it is how things turned out. The syntax is exactly that of C, all the way down to braces and statement terminators.
The main body of the configuration file consists of object definitions: sources, destinations, logpaths define which log message are received and where they are sent. All identifiers, option names and attributes, and any other strings used in the syslog-ng configuration file are case sensitive. Object definitions (also called statements) have the following syntax:
type-of-the-object identifier-of-the-object {<parameters>};
Type of the object: One of source, destination, log, filter, parser, rewrite rule, or template.
Identifier of the object: A unique name identifying the object. When using a reserved word as an identifier, enclose the identifier in quotation marks.
All identifiers, attributes, and any other strings used in the syslog-ng configuration file are case sensitive.
Use identifiers that refer to the type of the object they identify. For example, prefix source objects with s_, destinations with d_, and so on.
Repeating a definition of an object (that is, defining the same object with the same id more than once) is not allowed, unless you use the @define allow-config-dups 1 definition in the configuration file.
Parameters: The parameters of the object, enclosed in braces {parameters}.
Semicolon: Object definitions end with a semicolon (;).
For example, the following line defines a source and calls it s_internal.
source s_internal { internal(); };
The object can be later referenced in other statements using its ID, for example, the previous source is used as a parameter of the following log statement:
log { source(s_internal); destination(d_file); };
The parameters and options within a statement are similar to function calls of the C programming language: the name of the option followed by a list of its parameters enclosed within brackets and terminated with a semicolon.
option(parameter1, parameter2); option2(parameter1, parameter2);
For example, the file() driver in the following source statement has three options: the filename (/var/log/apache/access.log), follow-freq(), and flags(). The follow-freq() option also has a parameter, while the flags() option has two parameters.
source s_tail { file("/var/log/apache/access.log" follow-freq(1) flags(no-parse, validate-utf8)); };
Objects may have required and optional parameters. Required parameters are positional, meaning that they must be specified in a defined order. Optional parameters can be specified in any order using the option(value) format. If a parameter (optional or required) is not specified, its default value is used. The parameters and their default values are listed in the reference section of the particular object.
The unix-stream() source driver has a single required argument: the name of the socket to listen on. Optional parameters follow the socket name in any order, so the following source definitions have the same effect:
source s_demo_stream1 { unix-stream("<path-to-socket>" max-connections(10) group(log)); }; source s_demo_stream2 { unix-stream("<path-to-socket>" group(log) max-connections(10)); };
Some options are global options, or can be set globally, for example, whether syslog-ng OSE should use DNS resolution to resolve IP addresses. Global options are detailed in Global options of syslog-ng OSE.
options { use-dns(no); };
Objects can be used before definition.
Objects can be defined inline as well. This is useful if you use the object only once (for example, a filter). For details, see Defining configuration objects inline.
To add comments to the configuration file, start a line with # and write your comments. These lines are ignored by syslog-ng.
# Comment: This is a stream source source s_demo_stream { unix-stream("<path-to-socket>" max-connections(10) group(log)); };
Before activating a new configuration, check that your configuration file is syntactically correct using the syslog-ng --syntax-only command.
To activate the configuration, reload the configuration of syslog-ng using the /etc/init.d/syslog-ng reload command.
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