I've been trying to make Debian easier to install and use on Chromebooks
by adding integration to support their stock firmware/bootloader. The
major part of that work is 'depthcharge-tools' which manages
bootloader-specific stuff and kernel/initramfs upgrade hooks, recently
sponsored and now in the archive.

Another part of this is making d-i install a bootable system, where we
need to create a custom partition and then write a special image to it.
For these I have two udeb packages: 'partman-cros' [1] that does partman
integration and 'depthcharge-tools-installer' [2] which installs and
runs depthcharge-tools in-target.

I'd like these two udebs to be sponsored. I know I'm quite late with
these, but hoping it's not too late for bookworm installer changes. They
are somewhat small, `cat **/* | wc -l` gives around 400-600 lines each.
I tested them on the two Chromebooks I have (one arm64, one x86).

Here are the salsa links for the packages (I'd welcome moving them to
the installer-team namespace), they are on mentors.debian.net as well if
anyone prefers a dsc + tarball:

[1] https://salsa.debian.org/alpernebbi/partman-cros
[2] https://salsa.debian.org/alpernebbi/depthcharge-tools-installer

They can be tested on non-ChromeOS devices as well (a VM or actual UEFI
hardware), by roughly doing:

- Build both my packages above and save the two resulting udeb files
- Clone https://salsa.debian.org/installer-team/debian-installer
- Place the newly built udebs in build/localudebs
- Create a build/pkg-lists/local file with contents:
    live-installer -
- (without indents, and the '-' on the last line is intentional)
- Build that as a Debian package (or see its README for build details)
  - Check the resulting debian-installer-images tar.gz file for images
  - Extract netboot/gtk/mini.iso
- Boot a QEMU VM with it as cdrom, and a disk image to install to
- Prepend "cros_secure" to the kernel cmdline in the GRUB menu
- Follow the installer prompts (ideally everything should be obvious)
  - There's a warning if you don't create ChromeOS Kernel partitions
  - Create one big enough (512MB is great) or get error at the very end
- (The GRUB installation step will be skipped, manually run it
afterwards if you want to UEFI boot into the resulting system)

That should go through the most likely case. There's custom logic to ask
to make initramfs smaller if it doesn't fit the board's size limit, but
never triggered on x86 due to arch differences. If you do an arm64 build
you can test that by adding "depthcharge-tools-installer/board=kevin" to
the kernel cmdline.

It's harder to test on chromebooks the native way. On the boards I have,
the d-i netboot builds either doesn't fit the board's size limit (arm64)
or doesn't show any graphics (x86). But using a secondary bootloader and
adding the 'cros_secure' via GRUB works well to bootstrap their native
boot flow. (I can try to provide instructions if anyone wants, but this
email's already rather long.)

There are some more details and screenshots of the whole thing at my
DebConf22 talk [3], though I've changed some things a bit since then.
AFAICT the next steps after this are modifying the debian-installer repo
to build custom images bootable this way and
kernel/initramfs/modules-udebs changes for more boards as needed...

[3] Solving "How Can I Run Debian on My Chromebook?" For Good

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