ceph-iscsi on Ubuntu / no attribute cluster about ceph-iscsi HOT 5 OPEN

server03 ~ # cat /etc/ceph/iscsi-gateway.cfg
[config]
# name of the *.conf file. A suitable conf file allowing access to the ceph
# cluster from the gateway node is required.
cluster_name = ceph

# Pool name where internal `gateway.conf` object is stored
pool = config_iscsi

# CephX client name
cluster_client_name = ceph.client.admin.keyring

# API settings.
# The api supports a number of options that allow you to tailor it to your
# local environment. If you want to run the api under https, you will need to
# create crt/key files that are compatible for each gateway node (i.e. not
# locked to a specific node). SSL crt and key files *must* be called
# iscsi-gateway.crt and iscsi-gateway.key and placed in /etc/ceph on *each*
# gateway node. With the SSL files in place, you can use api_secure = true
# to switch to https mode.

# To support the api, the bear minimum settings are;
api_secure = false

# Additional API configuration options are as follows (defaults shown);
api_user = admin
api_password = admin
api_port = 5000
trusted_ip_list = 127.0.0.1

# Refer to the ceph-iscsi-config/settings module for more options

server03 ~ # cat /etc/ceph/ceph.conf
[global]
fsid = 34f09a6f-7aa4-4645-beaa-87cfcce6ad08
mon_initial_members = server03
mon_host = 172.16.0.202
auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx
osd pool default size = 2
crush chooseleaf type = 0
osd pool default pg num = 64
osd pool default pgp num = 64

[client]
rbd cache = true
rbd cache policy = writeback
rbd cache size = 24Gb
rbd cache max dirty = 20Gb
rbd cache target dirty = 16Gb

server03 ~ # cat /var/log/rbd-target-api/rbd-target-api.log
...
2019-10-10 07:56:38,082    ERROR [rbd-target-api:2918:<module>()] - Unable to connect to the cluster (keyring missing?) - [errno 2] error connecting to the cluster
2019-10-10 07:56:38,084 CRITICAL [rbd-target-api:2736:halt()] - Unable to open/read the configuration object