ceph mount: libceph: no secret set (for auth_x protocol)

1. Problem

sudo mount.ceph ip:6789:/ /mnt/demofs/
mount error 22 = Invalid argument
sudo dmesg|tail
[1343874.057458] libceph: no secret set (for auth_x protocol)
[1343874.057469] libceph: error -22 on auth protocol 2 init
[1343874.057477] libceph: client34169 fsid 388fe838-f746-48cb-a067-2cf73859994d
[1343898.536751] libceph: no secret set (for auth_x protocol)
[1343898.536762] libceph: error -22 on auth protocol 2 init
[1343898.536771] libceph: client34172 fsid 388fe838-f746-48cb-a067-2cf73859994d

2. Fix

$sudo mount -t ceph 147.2.208.109:6789:/ /mnt/demofs/ -o name=admin,secret=`ceph-authtool -p ceph.client.admin.keyring`
$mount|grep ceph
147.2.208.109:6789:/ on /mnt/demofs type ceph (rw,relatime,name=admin,secret=<hidden>,acl)

3. ceph-fuse

Another way to mount cephfs:

$sudo ceph-fuse -m 147.2.208.109:6789 /mnt/demofs/