Bug#1102604: debian-installer: Rescue mode can not execute shell when root filesystem is btrfs

[Martin-Éric Racine <martin-eric.racine@iki.fi>]

On Thu, 10 Apr 2025 14:24:58 -0600 Tyler Riddle
<cardboardaardvark@gmail.com> wrote:
> Package: debian-installer
> Version: Trixie Alpha 1
> Severity: normal
> Tags: d-i
> X-Debbugs-Cc: cardboardaardvark@gmail.com, debian-boot@lists.debian.org
>
> Dear Maintainer,
>
> When using rescue mode with a root file system that is btrfs the option to
> launch a shell inside the root file system does not function. This is because
> when the Debian installer created the btrfs file system it setup a subvolume
> named rootfs and performed the install into it. When the file system is mounted
> in rescue mode it is not mounted using the subvolume so /target has a directory
> inside it named @rootfs and that directory is where the actual root file system
> is.

I've noticed the same. See #1102134.

The easy fix would be for the rescue mode to try '-o subvol=@rootfs'
first if the filesystem type is btrfs and only if that failed try
without the subvolume.

Martin-Éric