If InfluxDB uses significant amount of disk space, you can follow our guide and suppress data export for hosts. If it does not work for your case, you can reduce amount of metrics which it stores by default (7 days of metrics)
Open command line management interface for InfluxDB:
Delete old database (it will remove all data, please be careful):
drop database fastnetmon
And recreate it with new retention configuration (you can replace 7d by any value):
CREATE DATABASE fastnetmon WITH DURATION 7d REPLICATION 1 NAME fastnetmon_default_rp
After these changes, InfluxDB will remove automatically all metrics older then specified value.