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syslog-ng - Man Page

syslog-ng system logger application


syslog-ng [options]


This manual page is only an abstract, for the complete documentation of syslog-ng, see The Administrator Guide[1] or the official syslog-ng website[2].

The application is a flexible and highly scalable system logging application. Typically, syslog-ng is used to manage log messages and implement centralized logging, where the aim is to collect the log messages of several devices on a single, central log server. The different devices - called syslog-ng clients - all run syslog-ng, and collect the log messages from the various applications, files, and other sources. The clients send all important log messages to the remote syslog-ng server, where the server sorts and stores them.



Run process with the specified POSIX capability flags.

  • If the --no-caps option is not set, and the host supports CAP_SYSLOG, uses the following capabilities: "cap_net_bind_service, cap_net_broadcast, cap_net_raw, cap_dac_read_search, cap_dac_override, cap_chown, cap_fowner=p cap_syslog=ep"
  • If the --no-caps option is not set, and the host does not support CAP_SYSLOG, uses the following capabilities: "cap_net_bind_service, cap_net_broadcast, cap_net_raw,cap_dac_read_search, cap_dac_override, cap_chown, cap_fowner=p cap_sys_admin=ep"

For example:

/usr/local/sbin/syslog-ng -Fv --caps cap_sys_admin,cap_chown,cap_dac_override,cap_net_bind_service,cap_fowner=pi

Note that the capabilities are not case sensitive, the following command is also good: /usr/local/sbin/syslog-ng -Fv --caps CAP_SYS_ADMIN,CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_NET_BIND_SERVICE,CAP_FOWNER=pi

For details on the capability flags, see the following man pages: cap_from_text(3) and capabilities(7)

--cfgfile <file> or -f <file>

Use the specified configuration file.

--chroot <dir> or -C <dir>

Change root to the specified directory. The configuration file is read after chrooting so, the configuration file must be available within the chroot. That way it is also possible to reload the syslog-ng configuration after chrooting. However, note that the --user and --group options are resolved before chrooting.

--control <file> or -c <file>

Set the location of the syslog-ng control socket. Default value: /var/run/syslog-ng.ctl

--debug or -d

Start syslog-ng in debug mode.


Enable syslog-ng to write core files in case of a crash to help support and debugging.

--fd-limit <number>

Set the minimal number of required file descriptors (fd-s). This sets how many files syslog-ng can keep open simultaneously. Default value: 4096. Note that this does not override the global ulimit setting of the host.

--foreground or -F

Do not daemonize, run in the foreground. When running in the foreground, starts from the current directory ($CWD) so it can create core files (normally, starts from $PREFIX/var).

--group <group> or -g <group>

Switch to the specified group after initializing the configuration file.

--help or -h

Display a brief help message.


Display the list and description of the available modules. Available only in and later.


Run syslog-ng as root, without capability-support. This is the default behavior. On Linux, it is possible to run syslog-ng as non-root with capability-support if syslog-ng was compiled with the --enable-linux-caps option enabled. (Execute syslog-ng --version to display the list of enabled build parameters.)

To run with specific capabilities, use the --caps option.

--persist-file <persist-file> or -R <persist-file>

Set the path and name of the syslog-ng.persist file where the persistent options and data are stored.

--pidfile <pidfile> or -p <pidfile>

Set path to the PID file where the pid of the main process is stored.

--preprocess-into <output-file>

After processing the configuration file and resolving included files and variables, write the resulting configuration into the specified output file. Available only in and later.

--process-mode <mode>

Sets how to run syslog-ng: in the foreground (mainly used for debugging), in the background as a daemon, or in safe-background mode. By default, syslog-ng runs in safe-background mode. This mode creates a supervisor process called supervising syslog-ng , that restarts syslog-ng if it crashes.

--stderr or -e

Log internal messages of syslog-ng to stderr. Mainly used for debugging purposes in conjunction with the --foreground option. If not specified, syslog-ng will log such messages to its internal source.

--syntax-only or -s

Verify that the configuration file is syntactically correct and exit.

--user <user> or -u <user>

Switch to the specified user after initializing the configuration file (and optionally chrooting). Note that it is not possible to reload the syslog-ng configuration if the specified user has no privilege to create the /dev/log file.

--verbose or -v

Enable verbose logging used to troubleshoot syslog-ng.

--version or -V

Display version number and compilation information, and also the list and short description of the available modules. For detailed description of the available modules, see the --module-registry option.


Sets the number of worker threads can use, including the main thread. Note that certain operations in can use threads that are not limited by this option. This setting has effect only when is running in multithreaded mode. Available only in and later. See The 4.6 Administrator Guide for details.




See Also



For the detailed documentation of see The 4.6 Administrator Guide[3]

If you experience any problems or need help with syslog-ng, visit the syslog-ng mailing list[4].

For news and notifications about of syslog-ng, visit the syslog-ng blogs[5].


This manual page was written by the Balabit Documentation Team <documentation@balabit.com>.


  1. The  Administrator Guide
  2. the official syslog-ng website
  3. The  4.6 Administrator Guide
  4. syslog-ng mailing list
  5. syslog-ng blogs

Referenced By

dqtool(1), pdbtool(1), persist-tool(1), smartd(8), syslog-ng.conf(5), syslog-ng-ctl(1).

01/25/2024 4.6 The syslog-ng manual page