Re: [dm-crypt] Questions about LUKS on RAID5

[Anthony Mutiso <anm.mlist01@limuru.com>]

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I am no LUKS expert so are not able to respond to the LUKS question, but 
man mdadm does say that you can, but should not, set a specific UUID 
with --uuid on create.

By the way, does the fs pass an fsck?

Wolfgang Schindler wrote:
> Hello out there, sunny greetings from good old germany,
>
>
> Don't know if i'm in the right place here. I need some help as it's a 
> black doomed day, today, things went wrong as they sometimes do.......
> For a real long time i had two running RAID5's with LUKS encrypted 
> data on them. I had to change the system, so i setup a new machine, 
> with two new raid5's also encrypted with LUKS, of course with some 
> more data space. I sent the data over network. Anything worked fine 
> for some days.
> Now my system disk crashed. So i took another system disk from another 
> raid system and started up. One of the data raids was found 
> immediately and i could luksOpen it with my passphrase, the other one 
> could not be assembled.
> I tried some assembles with --force and --scan. Did not work.
> Now I had a real bad idea, late at night and lot's of other things to 
> do asides. I zeroed the superblocks of the devices belonging to the 
> raid that could not be assembled.
> I rebuilt the raid with the same parameters as before and it was 
> rebuilt. The raid was then found immediately.
> No problems until there, but when i was trying to luksOpen the raid, 
> my passphrase did not work.
> So i checked the sourcecode of cryptsetup-1.0.7 and saw that in 
> function LUKS_generate_phdr the UUID of the underlying Raid or Device 
> is used in some way.
> But, by recreating the RAID, the UUID of the RAID has changed. So far 
> so bad.
>
>
> Question 1:
> is this UUID used in any way for decryption?
> Question 2:
> Would it be a reasonable and walkable way to set back the UUID to the 
> older one (thanks God or whomever, it was noticed in the old 
> mdadm.conf) to get the decryption running again?
> Question 3:
> Do you know how to set back the UUID?
>
>
> Thanks for answering, otherwise my good datastuff was gone?? and i had 
> a real bad day.
>
>
> Cheers
> -- 
> Wolfgang Schindler
>
>
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