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

[Chuck Silvers <chuq%chuq.com@localhost>]

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.

-Chuck