Bug#370487: partitions get formated after unsure confirmation in graphical installer

[James Addison <jay@jp-hosting.net>]

Source: partman-base
Followup-For: Bug #370487

Hi Thomas,

I discovered this bug while wondering about some of the default options during
the disk partition configuration steps (also known as the 'partman' component)
in the Debian 12 (bookworm) alpha 2 installer.

Since disk partition configuration continues to be important, the partman steps
are still in place and the overall intent remains similar to your experience of
the Jun 2006 Debian installer: select an installation disk, determine a
partition layout, confirm the changes, and then write them to the selected disk.

I had two goals in mind:

  * To learn more about whether the default selection of 'no' before changes
    are written to disk makes sense (that's how I found your bugreport)

  * Check whether the bug you reported exists in the Debian 12 installer

Although the menu screens that are involved may vary based on the system
operator's selections during installation, there is currently a two-step
confirmation after a partitioning scheme is determined:

  1. The operator is given the choice to 'undo' the partitioning changes, or
     to 'finish' the partitioning and write the results to disk

  2. If the user selected 'finish', there is a further confirmation dialog --
     with no option to go 'back', and a default 'no', asking whether to write
     the changes to disk

If the user selects 'undo', or if 'no' is selected and the operator continues
from the second step, then the user is taken back to the 'partition disks'
menu without any changes being written to disk (I checked that the modification
time on the file-backed disk image I was using in testing had not been updated;
not a cast-iron guarantee, but a fairly strong indicator I think).

There is another edge case, though: a user can select an entire disk to install
to -- without any partitions.  In that case the confirmation flow is slightly
different:

  1. The operator is notified that they have selected an entire-device to
     install to, and they may 'go back' or they are given a no/yes choice to
     create an empty partition table.

I've confirmed that with either the 'go back' or 'no' choices from that dialog,
the file-backed disk image remains unmodified.

And to answer my own question that brought me here: I think that the default
of 'no' makes sense.  In some cases it could cause a small delay if the user
does not read the dialog text and attempts to continue -- but writing disk
partition changes can be risky, and so I do think it makes sense to use 'no'
as the default on those menus.

Perhaps my explanation could have been more concise, but I hope that provides
a relevant update for this bug ahead of Debian 12's release.