F10: something broken with lvm

[Gerry Reno]

Gerry Reno wrote:
> Gerry Reno wrote:
>> Jonathan Underwood wrote:
>>> 2009/4/22 Gerry Reno <greno at verizon.net>:
>>>  
>>>> Gerry Reno wrote:
>>>>   
>>>>> We just upgraded a number of machines to F10 and after a few weeks 
>>>>> I've
>>>>> noticed something wrong with lvm.  Some of our inhouse scripts are 
>>>>> breaking
>>>>> that deal with lvm.  When I look at /etc/fstab and mount I see 
>>>>> entries what
>>>>> used to look like:
>>>>> /dev/VolGroup00/LogVol01 /                      ext3    
>>>>> defaults        1
>>>>> 1
>>>>> getting changed to this:
>>>>> /dev/dm-3   /                     ext3   defaults      1 1
>>>>>
>>>>>
>>>>>
>>>>> Where does this '/dev/dm-3' device come from?  I don't find it 
>>>>> referenced
>>>>> in any of the lvm tool outputs.  Whatever caused this change to 
>>>>> happen
>>>>> please revert this back to just listing lv's in normal lvm 
>>>>> parlance please.
>>>>>  These mysterious changes are breaking things and are a complete 
>>>>> nuisance.
>>>>>  How do we go about undoing these changes and how do we prevent 
>>>>> this from
>>>>> happening again?
>>>>>
>>>>>
>>>>> Regards,
>>>>> Gerry
>>>>>
>>>>>       
>>>> No one responded to this inquiry and these mysterious changes 
>>>> continue to
>>>> happen.  How can we prevent this from happening?
>>>>     
>>>
>>> Not sure what would cause that. Perhaps related to this bug:
>>>
>>> https://bugzilla.redhat.com/show_bug.cgi?id=475773
>>>
>>> Can you look back through /var/log/yum.log to work out which set of
>>> package updates may have triggered the problem - that might provide a
>>> clue.
>>>
>>>   
>> Yes, that bug shows something similar but affecting mkinitrd.  These 
>> machines were upgraded from F9 and then began having these mysterious 
>> changes occur with these /dev/dm-N entries.  These devices bear no 
>> resemblence to any mdraid devices or LVM devices and our scripts 
>> completely croak with these devices.  Why are perfectly good devices 
>> being renamed to absolutely useless names?  All I want to know is how 
>> to stop whatever it is that is causing this.
>>
>> Regards,
>> Gerry
>>
> Filed bug:  https://bugzilla.redhat.com/show_bug.cgi?id=497246
>
> Regards,
> Gerry
>

This is till causing major headaches.
Once a system has had its device names changed to /dev/dm-N style then 
how are we supposed to know when there is a conflict with device 
mounting.  /proc/mounts will show our LVM mounting by it's normal LVM 
names such as /dev/mapper/VolGroup01-LogVol00 but 'blkid' will have no 
listing for this device under that name any longer.  It will have 
/dev/dm-N entries.  But how are we to correlate these devices?  If our 
scripts attempt to mount /dev/dm-1 because it has no mount showing under 
/proc/mounts the script gets an error because the same device is mounted 
as /dev/mapper/VolGroup01-LogVol00.  How are we to tell that these 
devices have the same UUID when 'blkid' only lists one of them?

Regards,
Gerry