git: 2c26d77d989a - main - Remove /boot/efi from mtree, missed in 0b7472b3d8d2.

[Rodney W. Grimes]

> On 3/3/21 5:25 PM, Warner Losh wrote:
> >
> >
> > On Wed, Mar 3, 2021 at 10:21 AM Nathan Whitehorn 
> > <nwhitehorn at freebsd.org <mailto:nwhitehorn at freebsd.org>> wrote:
> >
> >
> >
> >     On 3/3/21 11:53 AM, Warner Losh wrote:
> >     >
> >
> >     [clipping non-technical pre-history]
> >
> >
> > Thanks. re-reading it now, I think I was more grumpy than warranted. 
> > And for that I apologize. Thanks for omitting it from the rest of the 
> > thread.
> 
> No worries, this happens, especially with the pandemic. I know I've 
> definitely been more prickly this year than normal...
> 
> >     >
> >     >? ? ?The installer *does* mount the partition in advance, so checking
> >     >? ? ?whether
> >     >? ? ?there is a mounted file system is a perfectly reasonable test to
> >     >? ? ?do. We
> >     >? ? ?could also check fstab. I would like to understand what is
> >     actually
> >     >? ? ?wrong here first, though. Especially after this misfire --
> >     which is
> >     >? ? ?problematic for reasons that are still not clear to me, since
> >     >? ? ?there are
> >     >? ? ?a number of standard directories in hier(7) not in mtree --
> >     I want to
> >     >? ? ?make sure we actually do have consensus about what is
> >     changing and
> >     >? ? ?why.
> >     >
> >     >
> >     > At the top level, we default to having directories in mtree unless
> >     > there's a good reason not to. We disagree as to whether the
> >     installer
> >     > should take the presence or absence of the directory as a strong
> >     > enough reason to do something. I don't think that's a good reason.
> >     >
> >     > But leaving that aside, let's say we?wanted to reuse the install
> >     boot
> >     > part of the installer to update boot blocks as part of
> >     installworld.
> >     > If we can talk through that example w/o it in mtree, then we can
> >     leave
> >     > it out. The last time I worked through this, though, I thought I'd
> >     > talked myself into needing it.
> >
> >     > Looking at bootconfig, we could use machdep.bootmethod to
> >     determine if
> >     > we need to update the ESP. If we didn't use that, then the ESP
> >     > shouldn't be touched. This is, at the moment, x86 centric, but
> >     could
> >     > trivially be added to architectures (I'm happy to add it). This
> >     would
> >     > prevent the 'false positive' that's possible in cases where we've
> >     > installed UEFI then downgraded to BIOS because of some problem
> >     (though
> >     > purely in the context of the installer, I guess this isn't an
> >     issue).
> >     > Even with your approach, we'd bogusly update an ESP (though one
> >     could
> >     > argue you might want that). We could also change the code so that
> >     > 'unsupported' architectures just didn't update. This is why I think
> >     > it's a bit fragile to rely only on the directory being present. It
> >     > should have something mounted there. If you wanted to mkfs_dos?+
> >     mkdir
> >     > efi at the top level, you could check for that directory if you
> >     were
> >     > looking for a flag, though that would still update on a BIOS
> >     boot the
> >     > ESP, and prevent false positives if run as part of an update.
> >
> >     I think we would *want* to update an ESP that is mounted but not
> >     currently being used. If I set up a dual BIOS/EFI-boot system for
> >     some
> >     reason and happened to install an update while booted from BIOS, I
> >     would
> >     be deeply astonished if my configured-by-the-installer EFI bootloader
> >     did not also get updated.
> >
> >
> > Yea, it's unclear to me what POLA here is, to be honest. Some of that 
> > is driven by a deep desire not to accidentally update USB drives that 
> > have a bootable image on them as well, so that may overly color my 
> > thinking.
> 
> Agreed on all counts here.
> 
> >     (As an aside, I would also much rather the installer use an update
> >     utility to set up the ESP than have the update utility use the
> >     installer.)
> >
> >
> > Agreed. We can work towards that after the release. It would be better 
> > if we could accumulate the scripts from a number of different places, 
> > find a good way to make them callable from those places more easily 
> > and start to move that tribal knowledge back into the base system 
> > where it belongs, imho. Baptiste raised an important point years ago 
> > that we also need to think about doing that with a way to 'plug in' 
> > $NEWEST_CLOUD's packages, containers, layout such that they could 
> > provide the details and then the automation would just work with them 
> > too: image building, release customization, boot block update, etc.
> >
> >     So here's a proposal, now that everyone is in the CC list:
> >     - We add /boot/efi back to mtree, even though I find it kind of
> >     weird to
> >     have it there I think we're too close to the release to have a
> >     conclusion on this.
> >     - We have the installer check for either the ESP directory being an
> >     active mountpoint or being in the in-progress fstab, whichever is
> >     easiest to implement (they are equivalent for the installer).
> >
> >
> > I'm OK with both of these points. If others are opposed to the first 
> > one, I'm willing to see how people react to it in the upgrade path 
> > before changing it again. We should get closure on Ed's proposed 
> > change here. I think it's good and should go in right after your 
> > changes. I'd start on your changes, and give people until the morning 
> > to pipe up with any objections.
> Here's a patch to do this:
> https://reviews.freebsd.org/D29068
> 
> It takes several hours to do the full test of building world, building 
> release ISOs, and running them through qemu, so it will be a while yet 
> before I feel comfortable committing. But it's a two-line diff and the 
> pieces worked independently, so the chances it works are pretty high. 
> Comments appreciated.
> 
> >     If that seems OK, I'll post another review for the change.
> >
> >     > A long-term project I've had has been to try to update the boot
> >     blocks
> >     > as part of installworld or maybe as part of installboot. We have
> >     > really poor reuse as a project in this area. Every little
> >     > orchestration thing wrote its own thing, and all of them have
> >     done it
> >     > badly. I was hoping to be able to reuse this code, or modify the
> >     > installer to use whatever we come up with there. As part of that, I
> >     > had talked myself into thinking we always needed /boot/efi, but I'm
> >     > having trouble reconstructing why that is now though I know it
> >     had to
> >     > do with installed systems and bootstrapping issues... I know I was
> >     > worried about questions about 'why isn't /boot/efi on the system by
> >     > default so I can mount it' for people that have upgraded, but I
> >     recall
> >     > there was more to it than that. With it in mtree, an installworld
> >     > (even w/o an ESP update) would create it and people could mount
> >     it w/o
> >     > having to mkdir which they might make as $SOMETHING_ELSE. So I
> >     guess
> >     > that's a bit of a weak reason to absolutely require it in mtree.
> >
> >     Thanks a lot for the explanation. I'm agreed entirely about the
> >     problem
> >     and the difficulty -- hopefully this set of changes helps at least.
> >
> >
> > It does. It starts to get people to use the same mount point for the 
> > ESP and we can then constrain the problem a bit and where we can't 
> > constrain it we can parameterize it.
> >
> >     As for mtree, I was imagining this as something like /home, which
> >     is a
> >     standard part of the system but isn't part of mtree since it
> >     depends on
> >     local-system policy. It's also different from /home in that we
> >     *do* want
> >     it to be a standard place for updates, of course. I think there's
> >     really
> >     not a ton of precedent either way: we don't have any other mount
> >     points
> >     in there for file systems that may or may not exist depending on
> >     circumstances, as far as I can tell. My worry with having it in
> >     mtree is
> >     that having it exist but potentially be a directory rather than an
> >     actual ESP requires that update tools be a little smarter and errors
> >     will be a little less obvious, since updates that don't pay enough
> >     attention will be a bit more likely to splat files there assuming
> >     there
> >     is an ESP even if makes no sense. It's a weak consideration either
> >     way,
> >     I think.
> >
> >
> > Yea. After a few hours of reflection, I've found that I could go 
> > either way and am having trouble understanding why I was so dead set 
> > this morning on a particular way. Chalk it up to me being a little 
> > extra grumpy at surprise changes.
> >
> > This one seems less like local policy than /home, but there's still a 
> > local aspect: Do I mount by default, and where. I think we should 
> > always, though, have a fstab entry as we'll need to update it from 
> > time to time. Even Windows has a nominal drive that it uses to mount 
> > the ESP, even if it isn't mounted by default. That's used to update it 
> > when scripts and such need to do that (or if you're the victim of an 
> > upgrade script that did too much that now needs to be undone). I think 
> > we should be similar in that regard. This would also let us take the 
> > automation of updates to the next level if we can rely on some basic 
> > things.
> 
> That makes sense to me. There's also still the issue of non-EFI systems, 
> that differ only by install-time configuration from non-EFI systems. One 
> of my worries of having /boot/efi always exist is that a non-EFI system 
> may try to "update" the EFI by poking around in the empty /boot/efi and 
> think it has updated/installed something useful but has in reality done 
> nothing. But it's a tricky situation all around.

I would think that during an update, which for me implies a
system that is booted and running, that the definative answer
to "are we an EFI system that needs to update EFI code" is
infact machdep.bootmethod=EFI.  Existance/absence of a directory,
or an entry in /etc/fstab is a poor quality indicator.

Is it even possible to create a dual mode installed FreeBSD
system that boots in either BIOS or EFI mode?  I know we do that
for the installed media, but that is hybrid media, and I do
not think that the bsdinstall can create such an installation
on a disk.

> -Nathan
> > Warner
> >     > Warner
-- 
Rod Grimes                                                 rgrimes at freebsd.org