On Thu, 13 Jul 2023 13:53:24 -0500 (EDT)
"Jay F. Shachter" <j...@m5.chicago.il.us> wrote:

> 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,
> trashed.
> 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
> obsolete.
> (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
>                                 j...@m5.chicago.il.us
>                                 http://m5.chicago.il.us
>                         "Quidquid latine dictum sit, altum videtur"
Did you read the FAQ:
https://www.openbsd.org/faq/faq4.html#Multibooting ??

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