Re: unknown partition table starting with 2.6.28

[Bill Davidsen <davidsen@tmr.com>]

John Robinson wrote:
> On 01/02/2010 20:46, Bill Davidsen wrote:
>> John Robinson wrote:
>>> On 15/01/2010 23:58, Timothy D. Lenz wrote:
>>>> I am trying to update my kernel from 2.6.26.8 to the current .32. 
>>> [...]
>>>> Starting with .28 I am getting an error about unknown partition 
>>>> table for all 3 md's. md0 is boot and main programs, md1 is swap, 
>>>> md2 is mostly recordings storage for vdr. All 3 are raid 1 and raid 
>>>> is built in.
>>>
>>> Your md devices aren't partitioned so you can quite safely ignore 
>>> the warning. See also 
>>> http://marc.info/?l=linux-raid&m=125797242110594&w=2
>>
>> To clarify that a bit, the kernel can use several partition formats, 
>> and something in the partitions looks like a partition table but not 
>> a *valid* partition table. So the kernel warns that it doesn't 
>> recognize the table.
>>
>> I suspect that using a different superblock type would change 
>> (probably eliminate) this, putting the md information at the start of 
>> the partition, of in a bit or whatever makes the kernel happy. The 
>> kernel would make us happy if it checked for a valid md superblock at 
>> the *end* of the partition, but there may be reasons why that's 
>> undesirable.
>>
>> Finally, I'm less willing than John to say you can ignore it, any 
>> time something comes close enough to working (in an undesired way) to 
>> generate an error message, if there's a simple way to be sure the 
>> kernel doesn't try to use random data as a partition table, you might 
>> well want to take a step to prevent a problem now.
>>
>> I believe it arises out of all arrays being partitionable recently, 
>> again the details don't come to mid, I've been pretty head down on 
>> another project since November.
>
> I don't think this analysis is correct. Yes, the situation has arisen 
> out of all arrays - in fact all block devices - being partitionable, 
> but the warning's not because of something that looks like a dodgy 
> partition table, it is precisely what it says, a statement that the 
> device does not contain a valid partition table. I am essentially 
> repeating the contents of Doug Ledford's earlier post to this list, to 
> which I referred above.

But the question is, *should* it contain a valid partition table, or 
even anything which looks enough like a partition table to have the 
kernel look at it hard enough to think it's invalid? I have several 
devices on one system which contain essentially random data, and I don't 
see this, so I assume that my data never looks enough like a partition 
table to trigger this. At least to 2.6.33-rc6, which I did boot.

-- 
Bill Davidsen <davidsen@tmr.com>
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein