Hey Michael. I've looked further into this, and it seems to be even worse than originally thought.
udisks mounts the fs readable (actually even if it would mount it ro, it might still cause writes to it)... which may easily cause data corruption if a user unplugs a removable device... because there is no reason for him to believe that the fs will be automagically mounted. I'd even say this is a security issue seem my arguing at https://github.com/storaged-project/udisks/issues/1145#issuecomment-1637258668 . Upstream has some commits with respect to that issue... but (purely by the commit message) it would seem to me that they still do this unwarranted mounting for XFS/ext*. Would be great if any fixes, so upstream recognises the issue, could be pulled into Debian ASAP. :-) Also, perhaps you know anything about this: - me, opening LUKS container... Jul 17 03:22:22 heisenberg kernel: BTRFS: device label data-b-1 devid 1 transid 7188 /dev/dm-1 scanned by (udev-worker) (1086718) Jul 17 03:22:22 heisenberg kernel: BTRFS info (device dm-1): using crc32c (crc32c-intel) checksum algorithm Jul 17 03:22:22 heisenberg kernel: BTRFS info (device dm-1): using free space tree - even without any restart, udisks seems to do its foul play and already mount any new device, but that's not the point here Jul 17 03:22:22 heisenberg kernel: BTRFS info: devid 1 device path /dev/mapper/data-b-1_unformatted changed to /dev/dm-1 scanned by (udev-worker) (1086718) Jul 17 03:22:22 heisenberg kernel: BTRFS info: devid 1 device path /dev/dm-1 changed to /dev/mapper/data-b-1 scanned by (udev-worker) (1086718) => do you perhaps know anything about that "_unformatted"?? This seems new to me (and wrong, as there is an fs within the container). Not sure if it's from the udisks upgrade or perhaps the recent udev/system upgrade 254~rc2-3? Looks at least strange. Previously these messages looked like: 2023-06-21T12:58:53.840720+02:00 heisenberg kernel: [ 63.194874] BTRFS info: devid 1 device path /dev/mapper/data-b-1 changed to /dev/dm-0 scanned by (udev-worker) (2282) 2023-06-21T12:58:53.840720+02:00 heisenberg kernel: [ 63.197048] BTRFS info: devid 1 device path /dev/dm-0 changed to /dev/mapper/data-b-1 scanned by (udev-worker) (2282) (i.e. some back and forth renaming) Thanks :-) Chris.