[libvirt-users] Is there still no easier way to shrink a VM image?

[Leroy Tennison]

I have numerous qcow2 images which need to be reduced in size and have 
their maximum size (virtual size) reduced.  Physical disk space became 
so low that VMs "auto-paused" themselves, I moved enough images to solve 
the immediate problem but need to rectify the underlying issue.  It 
seems that qcow[2] files are grown in size such that the data inside of 
them takes about 50-60% of the space (does anyone know the actual 
algorithm or how to control it?).  Given the total physical disk space 
on the hypervisors, I need something more restrictive.

Our hypervisors are a mix of Ubuntu 14 or 16 LTS (qemu-img 2.2 or 2.5).  
After doing all the preparation (defragment, reduce OS partition size) 
"qemu-img resize" reports that shrinking isn't supported yet.  My web 
research indicates that, to accomplish this,  I have to:

    convert to raw

    shrink the image

    convert back to qcow[2]

    increase the image size to provide for some growth

I'm hoping I've missed something in my research and that someone knows 
an easier way.  I don't feel constrained to qemu-img but this is a 
production environment precluding consideration of experimental 
software.  Virt-resize, guestfish or any other reasonable option is fine 
with me.  Solutions or ideas?  Thanks.

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