Problem installing over previous OS when retaining shared data partition

[trueriver]

Qubes OS version:

R4.0

Affected component(s):

Installer iso (on USB stick)

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Steps to reproduce the behavior:

find a computer with an unwanted OS installed on its only disk. (I have ttried this from a Win 10 installation and from a pre-exisiting Qubes installation - my hunch is that the effect will occur with any OS

Create a new partition at the top end ot the disk (shrinking existing partitions if need be) - I will call this the "shared data" partition.

shutdown and reboot into the old OS (to verify that the disk is valid). Check the shared data partition is usable. Format it NTFS (if Windows) or ext4 (if Linux).

Optionally: put some data there, and reboot and check the data reads back OK within the old OS.

shutdown

reboot into Qubes R4.0 installer

When you get to the partitioning page it will say somethoing like 1.8Mb available.

Select "I want to make additional space available"

I unselected encryption (but I do not know if this makes any difference)

Click "Done", top left of screen

In the partitioner, delete all partitions except the shared data partition. The partitioner should show lots of space available.

Click done to exit the partitioner

Expected behavior:

Install proceeds as the partitioner confirmed there is pleanty of space

Actual behavior:

Install fails because the partitioner reverts to showing only 1.8Mb space (or whatever the figure was initially

General notes:

Conjecture: I guess the4 installer may not be allowijng for the fact that the partitions will be deleted in performing its initial sanity checks.

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Related issues:

Related issue to follow shortly