Why do we need vfs.root.mountfrom for zfs
Andriy Gapon
avg at FreeBSD.org
Mon Nov 19 20:53:09 UTC 2012
on 19/11/2012 21:25 vermaden said the following:
> the beadm already checks if its being run on FreeBSD 8.0 or later, but
> that can be inappropriate if the needed bits would be MFC to stable/7
> and then put into the 7.5-RELEASE (is there any chance? for that).
I don't expect that there ever will be 7.5 and I am not MFC-ing anything to
stable/7 now, because it is a "legacy" branch.
> So please decide if You want beadm to support the stable/7 branch.
Not up to me to decide...
> Yesterday I got that piece of information ,that vfs.root.mountfrom is
> not needed now. Can I assume that using vfs.root.mountfrom is
> harmless then?
For ZFS booting vfs.root.mountfrom now has a reasonable default value, that's
all. You can still use vfs.root.mountfrom or fstab, but in most cases it's just
potentially more confusing than the default (bootfs).
> I ask because if we remove that from beadm, then anything from
> 2012.06 and later will just work and everything before won't. As beadm
> already checks if its being used on FreeBSD 8.0 or later, removing the
> setting of vfs.root.mountfrom from beadm would probably make it
> 9.1+ exclusive only (along with 9.0-STABLE from 2012.06 or later of
> course).
>
> The needed bits will probably find its way into the stable/8, but as
> 8.3-RELEASE was released 2012.04, then the 8.4-RELEASE with needed
> bits would be probably available in late 2013, it would not be nice
> for 8.x users to force them to upgrade to 9.x series when its still
> possible to use beadm on 8.x (even in its limited form - without
> the boot menu BE selection).
I believe that 8.4 release process will start as soon as 9.1 is out of the door
(that's a very uncertain date, I know) and hopefully it will take not more than
a few weeks. So I'd hope for early 2013 or perhaps even late 2012. But
definitely not late 2013.
> Another solution may be checking the commit version (r243107)
> for needed features and then set (or not) the vfs.root.mountfrom
> option.
>
> I would like to hear your comments on these thoughts/solutions.
Potentially you could just for a branch+revision combination (or
__FreeBSD_version). But you can just keep using vfs.root.mountfrom.
BTW, please note that it is the version of loader that is important here.
--
Andriy Gapon
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