existing raid superblocks confuse/break the install

[ceg]

Binary package hint: partman-md

Partman fails if you try to set up raid with existing raid superblocks on some devices. (i.e. on re-installs/updates, if you want to reuse or even if you deleted exsiting raid partitions/devices.)

Partman may get confused as raid devices get set up after partman (re)creates a partition and it happens that there is an superblock (at the beginning or end). Udev/mdadm sets it (partially) up and devices are in use.

The common workaround suggested is to make sure to allways "mdadm --zero-superblock" raid partitions/devices prior to deleting them, or to to "just zero the entire disk between reinstallation attempts" (often heard after bad experiences).

But partman-md should probably really watch out for/expect to see md devices being set up, (with udev/mdadm even after booting) and take them into account. (list them, offer to --stop, re-assemble (use) them as a real non-auxiliary device (not md127 and up), --zero-superblock if needed, ...)

related:
Bug #22301
Bug #33117
Bug #569900