# logstash > An Elasticsearch ETL (extract, transform and load) tool. > Commonly used to load data from various sources (such as databases and log files) into Elasticsearch. > More information: . - Check validity of a logstash configuration: `logstash --configtest --config {{logstash_config.conf}}` - Run logstash using configuration: `sudo logstash --config {{logstash_config.conf}}` - Run logstash with the most basic inline configuration string: `sudo logstash -e 'input {} filter {} output {}'`