[linux-lvm] what creates the symlinks in /dev/<volgroup> ?

[Chris Friesen]

Found it.  /usr/lib/udev/rules.d/11-dm-lvm.rules is what makes the 
/dev/<VG>/<LV> symlink for normal devices, but for a thin pool with a thin 
volume in it it will exit without making a symlink because 
DM_UDEV_DISABLE_SUBSYSTEM_RULES_FLAG=1 is set.

Given that both vgmknodes and the udev rules come from the lvm2 package, it'd be 
nice if they agreed on whether or not a symlink should be created and if so 
where it should link to.

Chris


On 06/20/2016 03:53 PM, Chris Friesen wrote:
> If I run it I get this:
>
> controller-1:/dev# vgmknodes -v
>      Using logical volume(s) on command line.
>      Found same device /dev/sda6 with same pvid Fw6C1IZABbnspIT23RbOGf2DXuB4zMhS
>      Found same device /dev/sda5 with same pvid 1s1dPDodojAS0kqToIRy4hiXFjCp2t2o
>      Found same device /dev/sda6 with same pvid Fw6C1IZABbnspIT23RbOGf2DXuB4zMhS
>      Found same device /dev/drbd4 with same pvid 6yk0HVTSbU9Amo6mwPKt3nZPnBIXBlhR
>      Found same device /dev/sda5 with same pvid 1s1dPDodojAS0kqToIRy4hiXFjCp2t2o
>    The link /dev/cinder-volumes/cinder-volumes-pool should have been created by
> udev but it was not found. Falling back to direct link creation.
>
>
> So it thinks that udev should have already made it.  Also, the symlink it
> generates looks different than the symlinks already in /dev/cinder-volumes, in
> that it points to /dev/mapper/<name> rather than pointing to the "real"
> /dev/dm-X device like the others.
>
>
> controller-1:/dev# ls -l /dev/cinder-volumes/
> total 0
> lrwxrwxrwx 1 root root  7 Jun 20 17:57 anchor-lv -> ../dm-9
> lrwxrwxrwx 1 root root 49 Jun 20 21:48 cinder-volumes-pool ->
> /dev/mapper/cinder--volumes-cinder--volumes--pool
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-0bc1df18-45d0-4477-9c57-36876d3f82d4 -> ../dm-19
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-2fff261f-8860-4b86-8b2e-49bddcf47e9b -> ../dm-17
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-48744604-6b02-4f11-ba02-3f692d109953 -> ../dm-15
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-8dabc793-e46d-4849-a2fb-dd3d4bc2c988 -> ../dm-20
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-be3c9ddb-a6eb-43ca-ac37-5554756a4c13 -> ../dm-16
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-eef89318-fa8e-4ca2-a8a7-fe8e143d8792 -> ../dm-14
> lrwxrwxrwx 1 root root  8 Jun 20 17:57
> volume-f11a7d88-1ad3-4e89-a594-e824019725bb -> ../dm-18
>
>
> Given the above, I think that something other than vgmknodes must be involved.
>
> Chris
>
>
> On 06/20/2016 03:03 PM, Ilya Boka wrote:
>> Command vgmknodes
>>
>> On Mon, Jun 20, 2016 at 10:52 PM, Chris Friesen
>> <chris.friesen at windriver.com> wrote:
>>> Hi,
>>>
>>> Can someone tell me what creates the /dev/<volgroup>/<volume symlinks?  Is
>>> this LVM or udev (and if udev, do you know which rule)?
>>>
>>> I'm seeing some interesting behaviour where if I create a thin pool it
>>> creates a symlink for the pool, but once I create a thin volume within the
>>> pool then the pool symlink disappears.
>>>
>>> Thanks,
>>> Chris
>>>
>>> _______________________________________________
>>> linux-lvm mailing list
>>> linux-lvm at redhat.com
>>> https://www.redhat.com/mailman/listinfo/linux-lvm
>>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
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>>
>