Upgrading 8.1 -> 9.x with ZFS rroot

[Matthew Seaman]

On 24/12/2013 01:13, Gene wrote:
> I'm planning to move from my current FBSD 8.1 (amd64) to 9.2. My concern is 
> that i'm using ZFS complete with a zfs root and I need to be sure that I don't 
> manage to screw up that root. Can someone point me to some good reading on ths 
> subject -
> 

If you're using ZFS then boot environments are your friend.  Essentially
you can set up a boot environment, upgrade everything to 9.2 inside it,
activate it and reboot.  If the new system doesn't work correctly, then
you can re-activate your original 8.1 system and revert.
Start by installing the beadm(1) utility from ports.  Tip: you can mount
a boot environment onto your running system using beadm, and chroot(8)
into it to upgrade it, but you will need mount a devfs instance on it as
well:

   # beadm mount YOURBEINSTANCE /mnt
   # mount -t devfs devfs /mnt/dev
   # chroot /mnt

   ... work on the BE ...

   # exit
   # umount /mnt/dev
   # beadm umount YOURBEINSTANCE


There are some incompatible changes to the on-disk formats between ZFS
on 8.1 and 9.2: in general, 9.2 will be perfectly happy with ZFS from
8.1, but not vice-versa.  So don't run 'zpool upgrade' or 'zfs upgrade'
until you are entirely happy with your new 9.2 setup.

Also, there have been incompatible changes to things like gptzfsboot --
here the new gptzfsboot introduces some pretty useful new functionality,
but again, it's not backwardly compatible.  I've a feeling it may not be
forwards compatible either...  Make sure you have bootable media for
each of the different versions you're working with, as that makes it
fairly simple to copy a matching set of boot blocks when needed.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.

PGP: http://www.infracaninophile.co.uk/pgpkey
JID: matthew at infracaninophile.co.uk

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