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Date: Sun, 25 Jul 2010 20:49:42 +0300
From: Andriy Gapon <avg@icyb.net.ua>
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To: Olivier Smedts <olivier@gid0.org>
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Cc: freebsd-fs@freebsd.org
Subject: Re: zfs loader: allow access to any filesystem in a pool
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on 25/07/2010 19:51 Olivier Smedts said the following:
> 2010/7/25 Andriy Gapon <avg@icyb.net.ua>:
>> This is a ZFS boot patch that I would like to present you for review and testing:
>> http://people.freebsd.org/~avg/zfsboot.diff
>>
>> Currently in zfsloader you can only switch between pools, but you can only
>> access one predetermined filesystem within a pool - wither root dataset of a
>> pool or a filesystem pointed to by bootfs pool property.
>> With this patch it is possible to access any filesystem in a pool and, thus, to
>> boot kernel and modules from an alternative filesystem.  This is another
>> stepping stone in so called Boot Environments support.
>>
>> An example.
>> You can boot kernel from a different filesystem by doing the following at the
>> loader prompt:
>> set currdev=zfs:tank/some/fs:
> 
> Can you specify a snapshot ? For example
> set currdev=zfs:tank/rootfs@20100722:
> 
> I never tried this, but it would be really great in case of a broken
> kernel/world.

Potentially there is nothing preventing a snapshot to be used as a boot dataset.
But I have not implemented this.

-- 
Andriy Gapon