[linux-lvm] Proper way to remove a qemu-nbd-mounted volume using lvm

Leroy Tennison leroy.tennison at verizon.net
Wed Apr 26 04:21:37 UTC 2017

I either haven't searched for the right thing or the web doesn't contain 
the answer.

I have used the following to mount an image and now I need to know the 
proper way to reverse the process.

     qemu-nbd -c /dev/nbd0 <qcow2 image using lvm>

     vgscan --cache    (had to use --cache to get the qemu-nbd volume to 
be recognized, lvmetad is running)

     vgchange -ay


     mount <selected qemu-nbd related 'LV Path' found from lvdisplay 
above> <mount point>

I made the changes I needed to make and have done the following:

     umount <mount point>

     lvchange -an <all qemu-nbd related 'LV Path's found from lvdisplay 

     vgchange -an <qemu-nbd related volume>

Now what?  How do I get the volume out of the list so I can use 
'qemu-nbd -d /dev/nbd0' to dis-associate the image with /dev/nbd0?  
vgreduce seems to be for volumes which have multiple underlying 
devices.  I started to use vgremove but, when it started prompting for 
confirmation about removing logical volumes, I wasn't sure exactly what 
it was going to do and responded 'no'.

If there is a web reference explaining this specific situation just 
point me to it - I'm not opposed to reading.  Thanks for the help.

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