Re: persistent removed MD referrence on reboot

[linbloke <linbloke@fastmail.fm>]

On 1/08/12 11:43 AM, Skip Coombe wrote:
> Thanks for the quick response.
>
> I did "dd -if=/dev/zero -of=/dev/sdc" and modified the the partition to 83.
>
> Today I followed your advice to investigate initrd. I deleted all the
> ARRAY specs from /etc/mdadm/mdadm.conf (they were
> from the time of installing 12-4, including the md2 ARRAY), wrote the
> new initrd, and rebooted.

I think Adam led you to the right path. Your reference to 12-4 leads me 
to guess that you're running Ubuntu 12.04? For me on these systems, I 
would do the following:

- zero superblocks:

sudo mdadm --zero-superblock /dev/sdc1

running that commands multiple times until they return "No superblock 
found" or similar message. Once you get that response, there are no 
mdadm superblocks remaining.

- update /etc/mdadm/mdadm.conf to remove references to old md arrays.
- update initramfs:

update-initramfs -u



 From there you should be able to reboot and find only those arrays 
specified in mdadm.conf (also arrays auto-built by the kernel from 
devices with partitions of type fd). If you're still not getting the 
expected outcome, pls send the output of "parted -l" and 
/etc/mdadm/mdadm.conf, uname -a, mdadm -V

HTH
j


> The reference to md2 went away, but now I see
> ======================
> $ cat /proc/mdstat
> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
> [raid4] [raid10]
> md127 : inactive sdc[1](S)
>        488385560 blocks super 1.2
>
> unused devices:<none>
> ======================
>
> I will repeat after "rm -rf /etc/mdadm" from the initrd dir tree. If
> that does not work I will probably just reinstall 12-4. I hate to do
> all the config again, but I've burned too many hours on this already.
> There are no superblocks left so I hope to get a clean start.
>
> n.b. md127 seems to be the default array, but still sdc is identified.
> There must be more info buried in the initrd.
>
> Thanks for the good advice, but I am still missing something.
>
> Skip
>
> On Mon, Jul 30, 2012 at 9:26 PM, Adam Goryachev
> <adam@websitemanagers.com.au>  wrote:
>> On 07/31/2012 11:02 AM, Skip Coombe wrote:
>>> I have an md entry referring to a badly removed RAID1 device (by me) after
>>> the associated device crashed (can't afford a replacement drive at this
>>> time).
>>> Despite attempts to remove the reference, after a reboot I see:
>>>
>>> ================================
>>> $ cat /proc/mdstat
>>> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
>>> [raid4]
>>> [raid10]
>>> md2 : inactive sdc[1](S)
>>>         488385560 blocks super 1.2
>>>
>>> unused devices:<none>
>>> ================================
>>>
>>> I am trying to repurpose the good drive as a not-RAID device. I have done
>>> sudo mdadm --zero-superblock /dev/sdc
>>> and
>>> sudo mdadm --zero-superblock --force /dev/sdc
>>> and even low level formatted /dev/sdc
>> What do you mean "low level formatted"? Have you done a
>> dd if=/dev/zero of=/dev/sdc
>>
>>> ================================
>>> $ ls /etc/mdadm/mdadm.conf
>>> ls: cannot access /etc/mdadm/mdadm.conf: No such file or directory
>>> ================================
>> Did you update the initrd file? This file probably contains a copy of the
>> mdadm.conf
>>
>> Also, did you modify the partition type, from fd to 83
>> I would suggest running the above dd command, which will erase ALL traces of
>> anything, including any data on the drive (so back it up elsewhere first).
>>
>> Most likely, the md code looks at a couple of different places on the drive
>> for the md information, so when you run the zero-superblock, it is only
>> erasing one of the possible locations. See man mdadm, especially the
>> --metadata section.
>>
>> Regards,
>> Adam
>
>