Filesystem type survives formatting in debian installer?

[Josef Wolf <jw@raven.inka.de>]

Hello!

I am trying to create a customized installation disk with the ability
to create encrypted root filesystem.  In my test installations, I noticed
that the filesystem type is not set properly when I choose to reformat
filesystems in debian installer.

This is what I am doing:

1. While doing a test install, I use "cryptsetup luksFormat /dev/hdaX"
   to create an encrypted filesystem.

2. In the next test install, I choose to reformat /dev/hdaX with ext3.

3. When the system reboots after installation, I get the error message
   that the filesystem could not be mounted causing the boot process to
   abort, and my preseed/late_command (which runs cryptsetup and copies
   the system to encrypted partition) is not run.

4. When I try to mount the filesystem manually, I get the error message
   that filesystem type cyrpto_LUKS in not known.

5. Using "mount -t ext3 /dev/hdaX /mnt" succeeds and "cat /proc/mounts"
   shows that the filesystem type is actually ext3, so the filesystem
   was actually reformatted.

Any ideas why the filesystem type is considered to be crypto_LUKS even
after it was reformatted with ext3?  I even tried to set the volume
label in the installer, but this did not help either.  After I mke2fs
manually, the filesystem type is recognized properly again.