Uberblock location

[Julian Elischer]

On 6/13/15 5:43 PM, felipemonteiro.carvalho at gmail.com wrote:
> hello,
>
> Where can I find the source code that you are mentioning? I am reading the source in https://github.com/zfsonlinux/zfs?files=1 but it is very large and so far I couldnt pinpoint where it finds the uberblock.

why are you posting to a FreeBSD mailing list and looking at Linux 
sources?
Our ZFS code is not there, but in

  https://svnweb.freebsd.org/base/head/sys/cddl/

I speak of the boot code
(at https://svnweb.freebsd.org/base/head/sys/boot/zfs/
specifically, and
https://svnweb.freebsd.org/base/head/sys/boot/
in general, because it is a 'stand alone' implementation of a ZFS reader.
it could be copied to run as a regular user process.

>
> Also the mention of bootblock confuses me since ita for booting while I am working in a general case, not necessarely involving boot.
>
> thanks,
>
> Felipe
>
> Enviada do meu iPhone
>
>> Em 12/06/2015, às 18:01, Julian Elischer <julian at freebsd.org> escreveu:
>>
>>> On 6/12/15 9:49 PM, Felipe Monteiro de Carvalho wrote:
>>> Hello,
>>>
>>> I am writing a program to read ZFS partitions, and although I already
>>> read a lot of documentation, there is 1 problem which is blocking me:
>>> How does the driver find the uberblock?
>>>
>>> I know, I can just get any test volume, find the ZFS uberblock and in
>>> my case it is positioned in 0x20C00 and there are lots and lots of
>>> copies (older versions?) of it.
>>>
>>> But there is no guarantee that it doesn't just happen to be in this
>>> position in my image and in another version it would be elsewhere, so
>>> I need the algorithm utilized to find it.
>> I presume you have looked at the zfs reading library in the bootblocks?
>>
>>> Any ideas?
>>>
>>> thanks,
>
>