Re: [PATCH] BIOS boot vs EFI system partition mountpoint

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Aug 20, 2022 at 04:14:46PM +0000, Taylor R Campbell wrote:
> > Date: Sat, 20 Aug 2022 20:45:29 +0700
> > From: Robert Elz <kre%munnari.OZ.AU@localhost>
> > 
> > Of course they wouldn't if they have installed the new version of the PBR
> > boot blocks, but I know of lots of people who essentially never do that.
> > They have happily done NetBSD upgrades (major version upgrades) without
> > touching anything outside the NetBSD filesystems.   At least since we
> > stopped encoding the /boot block numbers in the PBR boot code.   The boot
> > blocks work, updating them to something which should work, but who knows
> > since this is all BIOS using code, and no-one can test against every
> > ancient BOIS that ever existed, is dangerous.
> 
> Users who update these systems can either:
> 
> (a) leave the bootloader as is, and it will continue to work with no
> change, or
> 
> (b) update the primary bootloader with installboot and move /boot to
> /biosboot if they want to turn the existing image into a hybrid image
> that can also be booted with EFI (assuming it's already on a GPT).
> 
> Nothing in this change will automatically move /boot to /biosboot.  It
> will just cause new installations to use /biosboot instead of /boot
> (but still support /boot if you, e.g., untar an old file system's
> contents into a new file system).
> 
> What is the specific problem you foresee?

/boot can either be a directory or a file and upgrade tools will have to
deal with that (with the risk of ending up with an unbootable system if
things go wrong)

> 
> > Please leave /boot as it is (on x86 and arm and anything else that uses
> > something of that name) and make a new standard place for mounting the ESP.
> > That can be /efi (which I am currently using) or anywhere else that seems
> > reasonable (I can easily update my fstab), just not /boot (not on arm
> > systems either, unless there is some very good reason that it has to be
> > that way, which I very much doubt - the ESP should contain nothing that
> > is needed while the system is running, except when there is a need to
> > update it - my /efi is "noauto" in fstab, and I almost never mount it).
> 
> The EFI system partition is already mounted by default at /boot on
> evbarm and riscv.  That mount point serves a dual purpose both for efi
> boot and for fdt boot, and for related things like creds_msdos(8), so
> that, e.g., you can update device tree data by extracting a newer
> dtb.tgz.  The evbmips generic and octeon images also use /boot for dtb
> (not sure any of them boot with EFI).  x86 is the odd one out here.

To me it looks like easier and less error-prone to rename /boot to /efi
on these systems than change the purpose of exising /boot on x86.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--