Re: d-i rescue with btrfs rootfs
On 18/05/2025 at 16:16, Nicholas D Steeves wrote:
Pascal Hambourg <pascal@plouf.fr.eu.org> writes:
However it may not work with a system installed from Debian live with
Calamares which appears to set a different btrfs subvolume layout (see
#1104552). (...) so would it be desirable to add
(trivial) support for this case in d-i RC2 ?
(...)>> it would be good to know whether this layout comes from
Calamares upstream, the Debian package or Debian Live configuration.
I cloned everything that seemed relevant, and fairly quickly searched
and scanned, and what I found was that Calamares' btrfs layout can be
configured with a "mount.conf", but it sounds like only if one defaults
to btrfs. We default to ext4, so it falls back to hard-coded. As I
hypothesized, upstream Calamares appears to hard-code Ubuntu-style
layout
src/modules/mount/main.py
143: btrfs_subvolumes = [dict(mountPoint="/", subvolume="/@"), dict(mountPoint="/home", subvolume="/@home")]
(...)
TLDR: By doing this we would be supporting the Ubuntu layout becoming a
defacto bug-for-bug standard; this wastes the time and effort of
everyone who has already implemented flexible, configurable software,
and rewards supporting static "@, @home" systems to the exclusion of all
else. That's wrong, unjust, and not what Debian is supposed to do.
I understand your point of view, but it is also wrong and unjust to not
support installations done with the Debian Live installer. Also I doubt
that so many people use the Debian installer rescue mode to repair
Ubuntu installations.
If the priority is the inconsistent state, lets:
IMO the priority for Trixie is to support existing installations with
rescue mode. The hard freeze period has started, and I am afraid it is
too late for deeper changes.
1. Fix Calamares (#1104552 reassigned; MR submitted)
2. Decide if we're going to share the "@home" namespace with Ubuntu
and SUSE. If yes, and the priority is consistency, then we need to
start creating and mounting "@home" (which will sometimes already
exist).
IIUC the rationale for a @home subvolume is to exclude user data from
"system" snapshots. IIRC openSUSE also creates subvolumes for /var/log
and other parts of the filesystem. If Debian wants to do the same
without colliding with other distributions subvolume namespace, it could
use "@homefs".
Also I believe this topic exceeds the installer scope and should be
discussed more widely with other Debian developers.
3. Convert bugged installs to standard installs (this is easy, safe, and
revertible)
Really ?
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