[Ukfreebsd] Confused by ZFS root(s)

Peter Tribble peter.tribble at gmail.com
Mon Feb 5 18:30:30 GMT 2018

On Mon, Feb 5, 2018 at 1:00 PM, Jon Schneider <jon at axismilton.ltd.uk> wrote:

> On 05/02/2018 12:23, David Chisnall wrote:
>> 2) Why might my virtual machine not mount the important one
>>> zoot/ROOT/default ?
>> Do you already have something mounted at /?
> I mean having booted off memstick in my virtual machine when I do
> # zpool import zroot -fR /tmp/mnt
> the main root guts does not get mounted and I have to
> # zfs mount zroot/ROOT/default
> to get it. Whereas when I broke into the actual server I didn't have this
> issue. Clearly there is a difference and the main server seems to have been
> built mid 2014 but it too has a zroot/ROOT/default and I would like to
> understand the difference.

Assuming FreeBSD is similar to illumos in this regard, then the root
filesystem is mounted
very early in the boot process, by the boot process itself, so it's a bit
special. If you look
at the output of

zfs get canmount zroot/ROOT/default

it's probably set to 'noauto', which will disable automatic mounting. The
point here is that
you don't want / to get mounted a second time when the pool gets imported
later on in the
boot (or when 'zfs mount -a' gets run), so the behaviour you describe is as

-Peter Tribble
http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/

More information about the Ukfreebsd mailing list