root@ceph-rgw0:/etc/ceph# radosgw-admin user modify --max-buckets=1500 --uid=testuser
2016-06-01 03:38:43.950813 7f683f726900  0 RGWZoneParams::create(): error creating default zone params: (17) File exists
{
    "user_id": "testuser",
    "display_name": "First User",
    "email": "",
    "suspended": 0,
    "max_buckets": 1500,
    "auid": 0,
    "subusers": [
        {
            "id": "testuser:swift",
            "permissions": "full-control"
        }
    ],
    "keys": [
        {
            "user": "testuser",
            "access_key": "7EP1UJXSOVFA4TGPC40V",
            "secret_key": "oy5nlLrVRc3UC03TchKTYPMS0j7iZJIZrAwl73FH"
        }
    ],
    "swift_keys": [
        {
            "user": "testuser:swift",
            "secret_key": "KoGjzJwDPSQXKnFY8RwdgGrztesfqVysygCRkU8q"
        }
    ],
    "caps": [],
    "op_mask": "read, write, delete",
    "default_placement": "",
    "placement_tags": [],
    "bucket_quota": {
        "enabled": false,
        "max_size_kb": -1,
        "max_objects": -1
    },
    "user_quota": {
        "enabled": true,
        "max_size_kb": -1,
        "max_objects": 10
    },
    "temp_url_keys": []
}