Re: Upgrade from netbsd-9 to netbsd-10 potentially breaks ZFS mounts

[David Brownlee <abs%absd.org@localhost>]

On Mon, 11 Dec 2023 at 19:35, Chuck Silvers <chuq%chuq.com@localhost> wrote:
>
> On Wed, Nov 22, 2023 at 10:13:03AM +0000, David Brownlee wrote:
> > It looks like that between netbsd-9 and netbsd-10 the order of ZFS
> > mounts vs fstab has changed.
> >
> > I've just upgraded a system which had ffs filesystems for / & /home,
> > and a zfs pool on /home/files
> >
> > Before the upgrade the mount order was
> >
> > / (ffs)
> > /home (ffs)
> > /home/files (zfs)
> >
> > after upgrade the exact same configuration gives:
> >
> > / (ffs)
> > /home/files (zfs)
> > /home (ffs)
> >
> > resulting in /home/files being inaccessible. I'm not saying the new
> > order is wrong, it's just likely to break any existing configuration
> > which has a zfs mount on top of a non root filesystem in ffs...
> >
> > Does anyone have any thoughts on the best approach? - a note in
> > NetBSD-10 release notes and fstab/zfs manpage?
> >
> > David
>
> there's not really any defined order between ZFS mounting its file systems
> and the rc scripts mounting non-ZFS file systems.
>
> ZFS by default kind of assumes that it is managing all fs mounts and
> so it doesn't need to coordinate with anything non-ZFS to avoid this
> kind of problem.  the opt-out for this is to set the ZFS file system's
> "mountpoint" property to "legacy", and then ZFS won't mount it automatically
> and you can mount that specific ZFS fs via /etc/fstab to control the
> ordering the old fashioned way.

I'll definitely agree that both the netbsd-9 and netbsd-10 orders are
"reasonable", it's only the fact that it has changed that is an issue.

I'd suggest it might be worth a note in a manpage (fstab?) and the
netbsd-10 upgrade notes

David