Command Line Option

This article describes the fluentd command line options.

fluentd

Following are the fluentd command line options (fluentd -h):

Usage: fluentd [options]
-s, --setup [DIR=/etc/fluent] install sample configuration file to the directory
-c, --config PATH config file path (default: /etc/fluent/fluent.conf)
--dry-run Check fluentd setup is correct or not
--show-plugin-config=PLUGIN Show PLUGIN configuration and exit(ex: input:dummy)
-p, --plugin DIR add plugin directory
-I PATH add library path
-r NAME load library
-d, --daemon PIDFILE daemonize fluent process
--under-supervisor run fluent worker under supervisor (this option is NOT for users)
--no-supervisor run fluent worker without supervisor
--workers NUM specify the number of workers under supervisor
--user USER change user
--group GROUP change group
-o, --log PATH log file path
--log-rotate-age AGE generations to keep rotated log files
--log-rotate-size BYTES sets the byte size to rotate log files
--log-event-verbose enable log events during process startup/shutdown
-i CONFIG_STRING, inline config which is appended to the config file on-the-fly
--inline-config
--emit-error-log-interval SECONDS
suppress interval seconds of emit error logs
--suppress-repeated-stacktrace [VALUE]
suppress repeated stacktrace
--without-source invoke a fluentd without input plugins
--use-v1-config Use v1 configuration format (default)
--use-v0-config Use v0 configuration format
-v, --verbose increase verbose level (-v: debug, -vv: trace)
-q, --quiet decrease verbose level (-q: warn, -qq: error)
--suppress-config-dump suppress config dumping when fluentd starts
-g, --gemfile GEMFILE Gemfile path
-G, --gem-path GEM_INSTALL_PATH Gemfile install path (default: $(dirname $gemfile)/vendor/bundle)

Important Options

  • -g, --gemfile: Fluentd starts with bundler-managed dependent plugins.

  • --suppress-config-dump: Fluentd starts without configuration dump. If you do not want to show the configuration in fluentd logs, e.g. it contains private keys, then this options is useful.

  • --suppress-repeated-stacktrace: If true, suppresses the stacktrace in fluentd logs. Since v0.12, this option is true by default.

  • --without-source: Fluentd starts without input plugins. This option is useful for flushing buffers with no new incoming events.

  • -i, --inline-config: If fluentd is used on XaaS which does not support persistent disks, this option is useful.

  • --no-supervisor: If you want to use your supervisor tools, this option avoids double supervisor.

Set via Configuration File

Some options can be set via <system> directive via configuration file. See configuration file article for more on <system> directive.

fluent-cat

The fluent-cat command sends an event to fluentd in_forward/in_unix plugin. This is particularly useful for testing.

Here is its usage (fluent-cat --help):

Usage: fluent-cat [options] <tag>
-p, --port PORT fluent tcp port (default: 24224)
-h, --host HOST fluent host (default: 127.0.0.1)
-u, --unix use unix socket instead of tcp
-s, --socket PATH unix socket path (default: /var/run/fluent/fluent.sock)
-f, --format FORMAT input format (default: json)
--json same as: -f json
--msgpack same as: -f msgpack
--none same as: -f none
--message-key KEY key field for none format (default: message)

Example

Send JSON message with debug.log tag to the local fluentd instance:

echo '{"message":"hello"}' | fluent-cat debug.log

Send JSON message to an instance of fluentd on another machine on the network:

echo '{"message":"hello"}' | fluent-cat debug.log --host testserver --port 24225

fluent-plugin-config-format

It generates the formatted configuration document with the specified format for a plugin.

Here is its usage (fluent-plugin-config-format -h):

Usage: fluent-plugin-config-format [options] <type> <name>
Output plugin config definitions
Arguments:
type: input,output,filter,buffer,parser,formatter,storage
name: registered plugin name
Options:
--verbose Be verbose
-c, --compact Compact output
-f, --format=FORMAT Specify format. (markdown,txt,json)
-I PATH Add PATH to $LOAD_PATH
-r NAME Load library
-p, --plugin=DIR Add plugin directory

Example

Generate a README style document from plugin's config parameters:

fluent-plugin-config-format output null

Generate an old style output from plugin's config parameters:

fluent-plugin-config-format -f txt output null

fluent-plugin-generate

It generates Fluentd plugin project template. It is good for starting to Fluentd plugin development for using new API plugin. For more details, refer to the Generating plugin project skeleton section.

Here is its usage (fluent-plugin-generate -h);

Usage: fluent-plugin-generate [options] <type> <name>
Generate a project skeleton for creating a Fluentd plugin
Arguments:
type: input,output,filter,parser,formatter
name: Your plugin name
Options:
--[no-]license=NAME Specify license name (default: Apache-2.0)

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.