fluentd(1)
Fluentd is an open-source data collector that unifies logging across multiple sources and destinations.
Synopsis
fluentd [OPTION]... [-c CONFIG_FILE]Description
Fluentd is a lightweight, language-agnostic log aggregation daemon written in Ruby. It collects logs from various sources (files, syslog, HTTP, applications), parses them, buffers them, and routes them to multiple outputs (files, databases, cloud services, monitoring tools) in a unified way.
Fluentd uses a simple configuration file to define data flow with input plugins (sources), filter plugins (processing), and output plugins (destinations). It handles high-volume streaming data with minimal overhead and includes built-in reliability features like retries and buffering.
Common options
| Flag | What it does |
|---|---|
-c, --config FILE | Read configuration from specified file (default: /etc/fluent/fluent.conf) |
-d, --daemon PIDFILE | Run as daemon and write PID to specified file |
-v, --verbose | Enable verbose logging output |
-q, --quiet | Suppress verbose output; only show warnings and errors |
-l, --log FILE | Write log output to specified file instead of stdout |
--dry-run | Validate configuration file without starting the daemon |
-p, --plugin DIR | Add directory to plugin load path |
--emit-error-log-interval TIME | Set interval (seconds) for error log emission (default: 30s) |
Examples
Start Fluentd with the specified configuration file in foreground
fluentd -c /etc/fluent/fluent.confRun Fluentd as a daemon with PID file tracking
fluentd -c /etc/fluent/fluent.conf -d /var/run/fluentd.pidValidate the configuration file syntax without starting the service
fluentd --dry-run -c /etc/fluent/fluent.confStart Fluentd with verbose logging written to a log file
fluentd -c /etc/fluent/fluent.conf -l /var/log/fluentd.log -vStart Fluentd with custom plugin directory in the load path
fluentd -c /etc/fluent/fluent.conf -p /usr/lib/fluent/pluginsRun with minimal output; only warnings and errors are logged
fluentd -c fluent.conf -q