When using biggest_free, you are unable to specify a drive

Binary package hint: partman-auto

With the Dell factory process, we have a specific scheme that two partitions are created before Ubiquity (and consequently partman-auto) activate. These two partitions must remain in place.

In our seed file we are specifying:

     d-i partman-auto/init_automatically_partition select biggest_free
     d-i partman-auto/expert_recipe string ......

The expected behavior is that the expert_recipe is placed into the free space. This works properly when only a single drive is present.

When a second drive is added to the mix, it always chooses the bigger drive because it doesn't have those two existing partitions.

Logically, you might expect that it would be able to specify which disks to check like this:

     d-i partman-auto/disk string /dev/sda

Unfortunately, the biggest_free recipe ignores this variable. The only time it is used is when you also specify:

    d-i partman-auto/method string regular

In doing this, free space isn't taken into consideration at all. The recipe gets used, but wipes away both of the existing partitions on /dev/sda.

So I see two possible solutions:

1) Letting init_automatically_partition listen to the disk debconf option, and then restrict the disks it's allowed to check
2) Expand display.d/initial_auto to cover this case, perhaps adding a new method like regular_freespace.

The former option seems like a better solution though to me.