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List:       linux-lvm
Subject:    Re: [linux-lvm] New developer question -- API
From:       "Bryn M. Reeves" <breeves () redhat ! com>
Date:       2007-04-27 8:50:30
Message-ID: 4631B956.5020808 () redhat ! com
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John Antypas wrote:
> This has probably been asked thousands of times before, but I?ll try to
> be a good 1001 J
> 
>  
> 
> I?m trying to write some userspace code which can determine what  LV, VG
> and PV a givne file mout belongs to.  Yes, I can process the output of a
> few command lines tools like this:
> 
>  
> 
> 1.       Get the mount from /proc/mounts
> 
> 2.       Run lvs and map that into the LVM
> 
> 3.       Using the LVM, run vgs and get the VG
> 
> 4.       Using VG, use pvs and get the PV
> 
> 5.       Using PV, now some knowledge about how I set things up and get
> the md
> 
> 6.       Run around proc some more and figure out which disks this md is on
> 
>  
> 
> These utilities do it ? is there an API I can call to do all of this
> tracing down rather than processing shell processes?
> 

You can use liblvm2cmd to get this information (the header is normally
/usr/include/lvm2cmd.h). This allows you to run LVM2 commands through a
library interface, although you will still need to parse the output as
it is the same textual format as the commands themselves provide.

On a recent enough kernel though, all the information you are interested
in is exposed directly in sysfs. Take a look at the "holders" and
"slaves" entries in subdirectories of /sys/block. There is also a
library interface (libsysfs) that provides access to the keys & values
exposed here.

Regards,
Bryn.


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