Bug#992166: installation-reports: cannot install bootloader on JFS-on-mdraid, is this meant to work?

[Simon McVittie <smcv@debian.org>]

Package: installation-reports
Severity: normal

Boot method: USB
Image version: debian-live-11.0.0-amd64-xfce.iso release candidate, 2021-08-14
Date: 2021-08-14 approx 18:30 UTC

Machine: Lenovo Thinkpad X201, booted using BIOS
Partitions:

    (transcribed by hand, might not be 100% accurate - I'll get logs later
    but I wanted to report this while I still remember what I did)

    ~ # chroot /target sfdisk --dump /dev/sdb
    label: dos
    label-id: 0xbbfb3881
    device: /dev/sdb
    unit: sectors
    sector-size: 512

    /dev/sdb1 : start= 2048, size= 312578048, type=fd

    ~ # chroot /target lsblk
    NAME  MAJ:MIN RM   SIZE   RO TYPE  MOUNTPOINT
    sda     8:0    1     7.3G  0 disk
    |-sda1  8:1    1     2.3G  0 part  /media/cdrom
    `-sda2  8:2    1     2.6M  0 part
    sdb     8:16   0   149.1G  0 disk
    `-sdb1  8:17   0   149G    0 part
      `-md0 9:0    0   148.9G  0 raid1 /

    ~ # chroot /target mount
    /dev/md0 on / type jfs (rw,relatime)
    /dev/sda1 on /media/cdrom (etc.)
    devtmpfs on /dev type devtmpfs (etc.)
    proc on /proc (etc.)
    tmpfs on /run type tmpfs (etc.)
    sysfs on /sys (etc.)

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

Initial boot:           [O]
Detect network card:    [ ]
Configure network:      [ ]
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:    [E]
Overall install:        [E]

While working through the debian-cd testing checklist I tried to install
from the copy of d-i on the XFCE live image, onto a (degraded) RAID1 array
with a single JFS partition that is the root filesystem. Transcribed by
hand, formatting might not be 100% faithful but numbers should be correct:

    ~ # chroot /target lsblk
    NAME  MAJ:MIN RM   SIZE   RO TYPE  MOUNTPOINT
    sda     8:0    1     7.3G  0 disk
    |-sda1  8:1    1     2.3G  0 part  /media/cdrom
    `-sda2  8:2    1     2.6M  0 part
    sdb     8:16   0   149.1G  0 disk
    `-sdb1  8:17   0   149G    0 part
      `-md0 9:0    0   148.9G  0 raid1 /                 <-- a JFS filesystem

Note that I don't use JFS myself and I don't know whether this is expected
to be something that grub is able to cope with (#debian-cd regulars tell me
that they normally use a separate ext2 /boot partition outside the RAID array
when testing this use-case).

When trying to install the bootloader, I was prompted with this device list:

    /dev/sda (the USB stick I am installing from)
    /dev/sdb (the hard disk)

and I chose /dev/sdb. The result is:

    Install the GRUB boot loader
    -----------------------------
    Unable to install GRUB in /dev/md
    Executing 'grub-install /dev/md' failed.
    This is a fatal error.

I tried to work around this with:

    ~ # chroot /target grub-install /dev/md0

but this also failed with:

    grub-install: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
    grub-install: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
    grub-install: warning: File system `jfs' doesn't support embedding.
    grub-install: warning: Embedding is not possible.  GRUB can only be installed in this setup by using blocklists.  However, blocklists are UNRELIABLE and their use is discouraged..
    grub-install: error: will not proceed with blocklists.

I'll send logs when I've recovered them but I can't do that right now.

Again, I don't know whether this *should* work - I'm only testing it because
it was my interpretation of what was on the checklist.

    smcv