Ceph » ceph-volume

[root@ceph-nano-to-faa32aebf00b /]# ceph -v
ceph version 13.2.2 (02899bfda814146b021136e9d8e80eba494e1126) mimic (stable)

[root@ceph-nano-to-faa32aebf00b /]# ceph-volume lvm batch -h
-->  AttributeError: 'NoneType' object has no attribute 'startswith'

[root@ceph-nano-to-faa32aebf00b /]# cat /var/log/ceph/ceph-volume.log
[2018-09-28 09:25:38,800][ceph_volume.main][INFO  ] Running command: ceph-volume  lvm batch -h
[2018-09-28 09:25:38,800][ceph_volume.util.disk][ERROR ] unable to list block devices from: /dev/mapper
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ceph_volume/util/disk.py", line 260, in _map_dev_paths
    dev_names = os.listdir(_path)
OSError: [Errno 2] No such file or directory: '/dev/mapper'
[2018-09-28 09:25:38,801][ceph_volume][ERROR ] exception caught by decorator
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ceph_volume/decorators.py", line 59, in newfunc
    return f(*a, **kw)
  File "/usr/lib/python2.7/site-packages/ceph_volume/main.py", line 156, in main
    terminal.dispatch(self.mapper, subcommand_args)
  File "/usr/lib/python2.7/site-packages/ceph_volume/terminal.py", line 182, in dispatch
    instance.main()
  File "/usr/lib/python2.7/site-packages/ceph_volume/devices/lvm/main.py", line 40, in main
    terminal.dispatch(self.mapper, self.argv)
  File "/usr/lib/python2.7/site-packages/ceph_volume/terminal.py", line 182, in dispatch
    instance.main()
  File "/usr/lib/python2.7/site-packages/ceph_volume/decorators.py", line 16, in is_root
    return func(*a, **kw)
  File "/usr/lib/python2.7/site-packages/ceph_volume/devices/lvm/batch.py", line 156, in main
    description=self.print_help(),
  File "/usr/lib/python2.7/site-packages/ceph_volume/devices/lvm/batch.py", line 127, in print_help
    detected_devices=self.get_devices(),
  File "/usr/lib/python2.7/site-packages/ceph_volume/devices/lvm/batch.py", line 116, in get_devices
    all_devices = disk.get_devices()
  File "/usr/lib/python2.7/site-packages/ceph_volume/util/disk.py", line 619, in get_devices
    if is_mapper_device(diskname):
  File "/usr/lib/python2.7/site-packages/ceph_volume/util/disk.py", line 581, in is_mapper_device
    return device_name.startswith(('/dev/mapper', '/dev/dm-'))
AttributeError: 'NoneType' object has no attribute 'startswith'

This is running in a restricted container so /dev/mapper does not exist but asking for the help should not return an error.
The other calls (prepare, activate etc) are not affected, only batch.