I installed the `ceph` meta-package on a Debian 13 server, and then attempted to perform a manual installation of Ceph as described on <https://docs.ceph.com/en/reef/install/index_manual/#install-manual>. ceph-mgr failed to load modules, showing a "MGR_MODULE_DEPENDENCY: 13 mgr modules have failed dependencies" message in `ceph health detail`.
Logs for ceph-mgr show the below:

Jul 11 16:06:03 dp-1191 ceph-mgr[37463]: 2026-07-11T16:06:03.673+0000 7f7167a480c0 -1 mgr[py] Class not found in module 'iostat'
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]: 2026-07-11T16:06:03.673+0000 7f7167a480c0 -1 mgr[py] Error loading module 'iostat': (22) Invalid argument
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]: 2026-07-11T16:06:03.737+0000 7f7167a480c0 -1 mgr[py] Module not found: 'mgr_module'
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]: 2026-07-11T16:06:03.737+0000 7f7167a480c0 -1 mgr[py] Traceback (most recent call last):
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:   File "/usr/share/ceph/mgr/mgr_module.py", line 29, in <module>
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:     from mgr_util import profile_method
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:   File "/usr/share/ceph/mgr/mgr_util.py", line 6, in <module>
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:     import bcrypt
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:   File "/lib/python3/dist-packages/bcrypt/__init__.py", line 13, in <module>
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:     from ._bcrypt import (
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:     ...<11 lines>...
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]:     )
Jul 11 16:06:03 dp-1191 ceph-mgr[37463]: ImportError: PyO3 modules do not yet support subinterpreters, see https://github.com/PyO3/pyo3/issues/576

I am on Debian 13.5 and the installed Python version is 3.13.5.

This is an duplicate of #1102751. Apparently ceph-mgr uses subinterpreters and the native code of python3-bcrypt doesn't support this. previous versions allowed this silently, but with trixie this was turned into an Exception.
In upstream Ceph this was fixed a year ago[1], but there hasn't been an backport of this fix.

[1]: https://github.com/ceph/ceph/pull/62951

close 1102751 20.2.2+ds-1
thanks

Hi,

this is not an issue anymore with ceph 20, thus closing this bug.

Regards,
Danie