Re: [linux-lvm] lvremove: 'snapshot': can't remove 'active'? , non-mounted file system

[Ray Morris <support@bettercgi.com>]

>> lvremove -v /dev/Home/2010.06.27-06.18.55
>>    Using logical volume(s) on command line
>>  Can't remove open logical volume "2010.06.27-06.18.55"

   Does it have a partition which needs to be "released"? with kpartx  
-dv?
Try ls -al /dev/Home/2010.06.27-06.18.55*
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Ray Morris
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On 07/13/2010 01:34:13 AM, Luca Berra wrote:
> On Tue, Jun 29, 2010 at 07:07:29AM -0700, Linda A. Walsh wrote:
>> lvremove -v /dev/Home/2010.06.27-06.18.55
>>    Using logical volume(s) on command line
>>  Can't remove open logical volume "2010.06.27-06.18.55"
>> 
>> But it isn't mounted.
>> 
>> So why is it saying it is 'open':
> something is using it
> try looking in /sys/block/dm-4/holders, fuser, lsof ...
> 
>> ll /dev/mapper shows:
>> 
>> 
>> crw-rw---- 1  10, 58 2010-02-02 21:08 control
>> brw-r----- 1 252,  4 2010-02-02 21:08 Home-2010.06.27--06.18.55
>> brw-r----- 1 252,  3 2010-02-02 21:08 Home-2010.06.27--06.18.55-cow
>> brw-r----- 1 252,  2 2010-02-02 21:08 Home-Home
>> brw-r----- 1 252,  1 2010-02-02 21:08 Home-Home-real
>> brw-r----- 1 252,  0 2010-02-02 21:08 Home-Share
>> brw-r----- 1 252,  5 2010-02-02 21:08 Space-Backup
>> brw-r----- 1 252, 11 2010-06-29 06:40 Space-boot
>> brw-r----- 1 252,  6 2010-06-29 06:40 Space-root
>> brw-r----- 1 252,  7 2010-06-28 17:45 Space-Torrents
>> brw-r----- 1 252,  8 2010-06-29 06:40 Space-usr
>> brw-r----- 1 252,  9 2010-06-29 06:40 Space-var
>> brw-r----- 1 252, 10 2010-06-29 06:40 Space-var_cache
>> 
>> So 252 is the mapper device?
> 
> 252 is the dynamic major assigned to device-mapper on your system
> 
>> Is my real Home partition on 252,1?
> before you created the snapshot your Home device was
> /dev/mapper/Home-Home (aka dm-2)
> in order to create a snapshot lvm will use 4 devices
> 1) Home-Home-real (linear) which has the same mapping as Home-Home  
> before the
>    snapshot took place
> 2) Home-2010.06.27--06.18.55-cow (linear) which maps the space that  
> will
>    contains the COW data
> 3) Home-2010.06.27--06.18.55 (snapshot) this is a combination of (1)  
> and
>    (2) in order to show the visible snapshot
> 4) Home-Home (snapshot-origin) this device replaces your Home device
>    (keeping the same minor number)
> 
> so after taking the snapshot your Home device is still
> /dev/mapper/Home-Home, which maps to /dev/mapper/Home-Home-real, but
> before any write to /dev/mapper/Home-Home-real the original data is
> saved to Home-2010.06.27--06.18.55-cow, so Home-2010.06.27--06.18.55
> (which is based on Home-Home-real and Home-2010.06.27--06.18.55-cow)  
> will
> not change
> 
> please look also at linux/Documentation/device-mapper/snapshot.txt
> 
>> I just got a backup error when I tried to backup Home,
>> which would correspond to 252,2 above.  It thinks it
>> is no longer the same file system as the previous backup,
> details please
> 
>> Should I be backing up Home-Home-real?  That doesn't
>> seem right...
> usually one backs up the snapshot, which is supposed to be a
> point-in-time copy of the original, so i think you should backup
> Home-2010.06.27--06.18.55
> 
> L.
> 
>-- 
> Luca Berra -- bluca@comedia.it
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