Re: /sys/block and /dev and partitions

[Loic Dachary <loic@dachary.org>]

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Hi Sage,

On 15/08/2015 16:28, Sage Weil wrote:
> On Sat, 15 Aug 2015, Loic Dachary wrote:
>> Hi,
>>
>> Is there a portable and consistent way to figure out if a given /dev/XXX 
>> path (for instance /dev/dm-1) is a partition of a whole device ? 
>> Although checking /sys/block/dm-1/dm/name for a number at the end (like 
>> mpatha1 or mpatha2) would probably work, it feels like a fragile hack. 
>> Looking into /sys/block/dm-1/slaves will lead to 
>> /sys/block/dm-1/slaves/dm-0 and we can check that 
>> /sys/block/dm-*/subsystem is class/block. But that does not necessarily 
>> mean dm-1 is a partition of dm-0, just that it's a slave of dm-0.
> 
> Take a look at is_partition in ceph-disk, whih is the best I came up with.  
> Basically it checks if the device name appears as /sys/block/*/$foo...

That is consistently updated for /dev/sdb or /dev/vdb but things are different when using multipath. I'll rely on /sys/block/dm-?/dm/name instead until a better solution is found. 

Thanks !

> 
> sage
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-- 
Loïc Dachary, Artisan Logiciel Libre


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