From owner-freebsd-stable@freebsd.org  Tue Nov 22 14:35:39 2016
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Subject: Re: Help! two machines ran out of swap and corrupted their zpools!
To: freebsd-stable@freebsd.org
References: <583339F0.7050905@b1t.name>
 <E1c96fO-0004v1-Ef@dilbert.ingresso.co.uk>
From: Volodymyr Kostyrko <arcade@b1t.name>
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Date: Tue, 22 Nov 2016 16:35:33 +0200
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Pete French wrote:
>> zpool import -N -O readonly=on -f -R /mnt/somezpoool
>>
>> If that doesn't help try:
>>
>> zpool import -N -O readonly=on -f -R /mnt/somezpoool -Fn
>
> I got someone to do this (am still having toruble finding time
> as am supposed to be off sick) and it causes instant kernel panic
> on trying to import the pool. Same as it does on boot.

Instapanic, huh...

Ok, let's put documentation aside and focus on unsupported development 
features.

You'll need a list of available transactions:

zdb -ul <vdev>

This one when given a vdev lists all uberblocks with their respective 
transaction ids. You can take the highest one (it's not the last one) 
and try to mount pool with:

zpool import -N -O readonly=on -f -R /mnt/somezpool -F -T 
<transaction_id> <pool>

Then check available filesystems. If it breaks again - retry with older 
transaction id.


-- 
Sphinx of black quartz judge my vow.