partman/unmount_active is not preseedable

[Jonathan Reed]

The partman/unmount_active question is not preseedable. This is a problem.

Due to some other d-i bug introduced in trusty, the mountmedia command is extremely ... insistent, and when we re-install machines in an unattended mode, it finds /dev/sda1 (a /boot partition) and insists on mounting it on /media, even when anna/retriever is set to net-retriever. This causes partman to complain about mounted partitions. I should be able to pre-seed this question, but I can't, because it forces the seen flag to false. It is a bit presumptuous of d-i to think that it knows my installation environment better than I do: these are unattended machines installed over the network, and any mounted partitions should get overwritten. I do understand the desire not to accidentally scribble over installation media, but at the same time, consider letting sysadmins who know what they're doing preseed answers to questions here. If you're concerned, introduce another debconf key partman/disable_all_safety_checks or something that defaults to false.

For another example of people getting bitten by this problem, see:
http://ubuntuforums.org/showthread.php?t=2215103&p=12977473#post12977473

[Jonathan Reed (jdreed)]

And before someone bothers to point out that partman/filter_mounted is preseedable, that doesn't help. All that does is tell partman not to filter out mounted partitions. So if I set that to false, partman doesn't display the warning, but will attempt to create a partition on a mounted filesystem, which doesn't work. There is absolutely no way to tell partman "No, really, there should not be any local block devices mounted." short of forcing things in an early_command, which is a fairly large hammer.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Max Brustkern (nuclearbob)]

I can preseed this on xenial desktop and server images. I think this is resolved now.

[Azat Kurbanov (cordalace)]

But I cannot preseed this on xenial (server). See screenshot in attachement. I see "FSET partman/unmount_active seen false" instruction in debconf debug log.

[Stefan H (ilendir)]

#3 How did you preseed this away? I try to do this with a current xenial server image and it doesn't work.

I've looked through the syslog and found at one point that partman/unmount_active is set to true and later I see:

SUBST partman/unmount_active DISKS /dev/sda
Adding [DISKS] -> [/dev/sda]

and then

FSET partman/unmount_active seen false
0 false