Bug#1031622: d-i regression since bookworm alpha 1: creates a filesystem with FEATURE_C12 unsupported by the installed e2fsck

[Simon McVittie <smcv@debian.org>]

Package: installation-reports
Severity: grave
Justification: renders package unusable (at least for inexperienced users)
X-Debbugs-Cc: e2fsprogs@packages.debian.org

Boot method: virtual CD
Image version: https://cdimage.debian.org/cdimage/weekly-builds/amd64/iso-cd/debian-testing-amd64-netinst.iso dated 2023-02-09
Installation date: 2023-02-19

Machine: qemu VM, virt-manager "Debian testing" profile
Partitions: default guided partitioning on a 20G disk

Base System Installation Checklist:
[O] = OK, [E] = Error (please elaborate below), [ ] = didn't try it

Initial boot:           [O]
Detect network card:    [O]
Configure network:      [O]
Detect media:           [O]
Load installer modules: [O]
Clock/timezone setup:   [O]
User/password setup:    [O]
Detect hard drives:     [O]
Partition hard drives:  [O]
Install base system:    [O]
Install tasks:          [O]
Install boot loader:    [O]
Overall install:        [E]

Comments/Problems:

Steps to reproduce
==================

I used the graphical installer, and installed with mostly default settings
(in particular the default guided partitioning with all files in one
ext4 partition).

Non-default settings, just in case they matter (but I'm fairly sure they
don't):

* en_GB instead of en_US;
* an apt proxy (http://192.168.122.1:3142 to use apt-cacher-ng on my
  host system);
* tasksel: LXDE instead of the default GNOME, and add a ssh server

Expected result
===============

The installed system boots.

Actual result
=============

Graphical installation proceeded normally (in particular #1031620 is
fixed in this weekly build). However, on booting the installed system
for the first time, I got this error:

> /dev/vda1 has unsupported feature(s): FEATURE_C12
> e2fsck: Get a newer version of e2fsck!
> 
> /dev/vda1: ***** WARNING: Filesystem still has errors *****
> 
> fsck exited with status code 12
> The root filesystem on /dev/vda1 requires a manual fsck

followed by an (initramfs) prompt.

Workaround
==========

Reset the VM and boot with "fsck.mode=skip" added to the kernel
command-line in grub. After booting like that once, upgrade e2fsprogs from
version 1.46.6-1 (in bookworm) to version 1.47.0-1 (in sid). The initramfs
is rebuilt and the rebuilt version can successfully fsck the filesystem.

Speculation
===========

I think this could be caused by debian-installer having udebs from
e2fsprogs 1.47.0-1 in the installation environment, so that the version
used to create the root filesystem has newer feature flags than the
installed version of e2fsck can cope with (similar to #1030939 and
#1031325).

If that theory is correct, then I think that even if the e2fsprogs
maintainer considers it to be important for mke2fs to create new
filesystems with default feature flags that are unsupported by Debian 11,
as a minimum mke2fs should be avoiding new feature flags until an e2fsck
that supports those flags has migrated to testing.

    smcv