Eu encontrei o problema:
[dadmin@localhost dashboard]$ sudo tail /var/log/messages
May 11 16:21:41 localhost influxd: [I] 2017-05-11T14:21:41Z Using data dir: /dashboard/influxdb/data service=store
May 11 16:21:41 localhost influxd: run: open server: open tsdb store: open /dashboard/influxdb/data/_internal: permission denied
May 11 16:21:41 localhost systemd: influxdb.service: main process exited, code=exited, status=1/FAILURE
May 11 16:21:41 localhost systemd: Unit influxdb.service entered failed state.
May 11 16:21:41 localhost systemd: influxdb.service failed.
May 11 16:21:41 localhost systemd: influxdb.service holdoff time over, scheduling restart.
May 11 16:21:41 localhost systemd: start request repeated too quickly for influxdb.service
May 11 16:21:41 localhost systemd: Failed to start InfluxDB is an open-source, distributed, time series database.
May 11 16:21:41 localhost systemd: Unit influxdb.service entered failed state.
May 11 16:21:41 localhost systemd: influxdb.service failed.
Quando eu tinha executado
/usr/bin/influxd -config /dashboard/influxdb.conf
As pastas foram criadas com o dadmin como proprietário
Eu removi as pastas e reiniciei o serviço. Agora tudo funciona bem.