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Re: Bug#1000239: Rescue system won't find root partition, but insists on /usr

On Fri, Dec 03, 2021 at 04:08:24PM -0500, Nicholas D Steeves wrote:
> Control: severity -1 serious
> Control: tags = confirmed
> CCing the release team, and CTTE because I don't know who else is
> tracking issues related to the usrmerge effort.  I've consciously chosen
> not to pour gasoline on the flame war by CCing anyone else (nor will I
> contact anyone else about the existence of this bug).
> Steps I used to try to reproduce:
> 1. Downloaded debian-testing-amd64-netinst.iso	2021-12-03 16:21 408M
> 2. Installed to EFI-enabled qemu eg:
>    kvm -bios /usr/share/ovmf/bios.bin -m 2G \
>    -hda debian-separate-usr-sda.raw \
>    -cdrom debian-testing-amd64-netinst.iso
> 3. Guided partitioning with separate /home, then changed the mount point
>    to /usr.  Partition layout is:
>                                   sda1: ESP  fat32
>                                   sda2: /    ext4
>                                   sda3: swap swap
>                                   sda4: /usr ext4
> 4. Selected only "Standard System Utilities"
> 5. Rebooted
> Result: SUCCESS
> Then, to test the rescue functionality:
> 1. I discovered qemu+OVMF boot order is broken without changing the
>    command to: kvm -L /usr/share/ovmf/ -m 2G -boot menu=on \
>                    -hda /scratch/debian-separate-usr-sda.raw \
>                    -cdrom /scratch/debian-testing-amd64-netinst.iso
> 2. Selected sda2
> 3. Yes, mount /boot/efi
> 4. Execute a shell in /dev/sda2
> 5. No usable shell was found on your root file system (/dev/sda2)
> 6. Changed virtual terminal
> 7. cd /target && ls bin
>    ls: bin: No such file or directory
> Result: FAILED
> Conclusion: This is a usrmerged system, and the rescue system does not
> support usermerged systems.
> The options are, as I see them, ranked from least to most work-hours:
> 1. Debian isn't yet ready for usrmerge.  Revert to normal system installation.
> 2. Reassign to src:rescue, and fix the rescue system.
>    a) before chrooting, test for the presence of /target/bin/sh
>    b) if /bin/sh is not found, either emit error to the user and present a
>       dialogue for selecting /usr partition, or
>    c) parse /target/etc/fstab, and attempt to mount other partitions
>    d) b & c will be difficult to implement when attempting to accommodate
>       the heterogeneity of possible MD, LUKS, and LVM layouts, not to mention
>       the complications introduced by the possibility of a user-configured
>       btrfs subvolume name "@usr" on any valid device.  Fstab parsing might
>       make the btrfs case easier with:
>         i)   Display a dialogue selector if a btrfs partition is detected
>              The dialogue will list all detected subvolumes
>         ii)  If the user cannot find a subvolume for "@usr", then
>         iii) Allow the user to escape to the partition selection screen, and
>         iv)  Unmount the partition
> 3. Disallow configuring of a mount for "/usr", and *Prominently* declare that
>    Debian no longer supports separating /usr from /, declare this in *many
>    places*, and reply to bugs on this topic for many years.  I put this one
>    last because I believe the cost to work-hours is unbounded, and
>    because I believe there may be a negative social cost associated with
>    this action.  Also, if Fedora/RHEL/SUSE/Ubuntu support a separate /usr
>    partition, then this action could make Debian look inferior.

FWIW, Debian was the last holdout in still supporting a separate /usr
partition amongst major distributions, so that bit is irrelevant...


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