nats.docs/jetstream/getting_started/README.md

Getting Started

Getting started with JetStream is straightforward. While we speak of JetStream as if it is a separate component, it's actually a subsystem built into the NATS server that needs to be enabled.

Command Line

Enable JetStream by specifying the -js flag when starting the NATS server.

$ nats-server -js

Configuration File

You can also enable JetStream through a configuration file. By default, the JetStream subsytem will store data in the /tmp directory. Here's a minimal file that will store data in a local "nats" directory, suitable for development and local testing.

$ nats-server -c js.conf

# js.conf
jetstream {
   store_dir=nats
}

Normally JetStream will be run in clustered mode and will replicate data, so the best place to store JetStream data would be locally on a fast SSD. One should specifically avoid NAS or NFS storage for JetStream.

See Using Docker and Using Source for more information.