Esteemed Colleagues:

Every time I install OpenBSD (the latest version, 7.3), it trashes
GRUB, and renders my computer unbootable.  I am guessing, and please
correct me if I am wrong, that this is because OpenBSD puts its
subpartition table in disk storage that has not been given to it.

The internal hard drive is an MBR-partitioned disk belonging to a
computer that is configured to do Legacy boot.  Microsoft Windows,
Linux, and Haiku are already installed.  Microsoft Windows uses all
three primary partitions for itself, because that is what Windows
does, and every other operating system has to find a place for itself
within the extended partition.

The bootloader is GRUB2, and has been, since I installed the Linux
system.  The Linux system resides on two logical volumes (root and
swap) carved out of an LVM volume group that resides on the first
logical slice of the extended partition (which Linux calls /dev/sda5).
GRUB2 boots it by means of:

     insmod lvm
     set root=(lvm/m5-springdale)
     linux /boot/vmlinuz root=/dev/m5/springdale
     initrd /boot/initramfs.img

Haiku resides on the third logical slice of the extended partition,
which in Linux is called /dev/sda7, and is booted by means of:

     set root=(hd0,7)
     chainloader +1

OpenBSD was installed -- repeatedly -- in the second logical slice of
the extended partition, which in Linux is called /dev/sda6 (and I
intend to install NetBSD in /dev/sda9, I have a very subtle sense of
humor), and there is already a stanza in my GRUB menu that has been
made ready for it:

     set root=(hd0,6)
     chainloader +1

although I am also ready to boot it by means of kopenbsd, if necessary.

I never got to execute that stanza in the GRUB menu, however, because
the OpenBSD installation has always rendered my system unbootable.  It
just didn't boot, not even into the GRUB menu.  I had to repair my
system by booting from a recovery CD, mounting /dev/m5/springdale on,
e.g., /mnt, furnishing /mnt with appropriate proc, sys and dev
filesystems, doing a chroot to /mnt, and then doing a "grub2-install
/dev/sda".  Which failed, complaining, inter alia, about a disk with
multiple partition tables.  But if I did

      dd if=/dev/zero of=/dev/sda bs=512 skip=1 count=2

then grub2-install ceased complaining about a disk with multiple
partition tables, and it succeeded, and I could then reboot into the
GRUB menu.  But now OpenBSD was unbootable.

All of this has led me reasonably to theorize that OpenBSD puts its
subpartition table outside of the area that belongs to it, which is
the second logical slice of the extended partition, which is where I
tell it to install itself -- in particular, that it puts its
subpartition table near the MBR table, which is an area of disk that
does not belong to it, but, rather, to GRUB, which is, consequently,

If this is what is happening, then it is totally bogus.

I have nothing against subpartitioning.  Linux doesn't do it, but many
respectable operating systems do, like FreeBSD, NetBSD, and Solaris,
although Solaris, practically speaking, is usually installed so as to
use ZFS rather than UFS, so the entire concept of subpartitioning is

(Parenthetically, when is OpenBSD going to support ZFS, and join the
category of operating systems in which I can do serious work, i.e.,
Solaris, Linux, FreeBSD, and NetBSD?  NetBSD didn't use to be in that
category, because its implementation of ZFS was brain-damaged, but
now it has a good implementation of ZFS, and now it is a member in
good standing of the category of operating systems in which I can do
serious work.  OpenBSD is not, and in that regard it resembles Haiku,
or SkyOS, or Icaros, and that is regrettable, because OpenBSD has
other good features that would otherwise make me want to use it for
serious work.  But I digress.)

But my FreeBSD systems manage to do subpartitioning without trashing
GRUB and rendering my computers unbootable.  I assume that is because
FreeBSD doesn't overwrite disk storage that doesn't belong to it, but
that, rather, it keeps its subpartition table in the area of disk
where it has been told to install itself.

Now, I do not know for certain that OpenBSD overwrites parts of GRUB
with its subpartition table.  I am only theorizing, based on strong
circumstantial evidence.  What I do know is that every time I install
OpenBSD, it renders my computer unbootable.  How do I get it to stop
doing that?

Thank you in advance for any and all replies.

                        Jay F. Shachter
                        6424 North Whipple Street
                        Chicago IL  60645-4111
                                (1-773)7613784   landline
                                (1-410)9964737   GoogleVoice

                        "Quidquid latine dictum sit, altum videtur"

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