Rancher uses etcd as datastore. When using the Single Node Install, the embedded etcd is being used. The persistent data is at the following path in the container: /var/lib/rancher. You can bind mount a host volume to this location to preserve data on the host it is running on. When using RancherOS, please check what persistent storage directories you can use to store the data.

Command:
docker run -d --restart=unless-stopped \
  -p 80:80 -p 443:443 \
  -v /opt/rancher:/var/lib/rancher \
  rancher/rancher:latest