How to clean up unused qcow2 clusters

[Jakob Bohm]

Hi,

As is well known, qcow2 files contain a large number of
reference counted clusters that correspond roughly to file
system blocks.

As snapshots are deleted, many clusters will become logically
freed (they are no longer referenced by any image or snapshot).

My main question is how to remove, or at least zero out, those
unused host clusters, assuming the qcow2 file is not busy (because
the virtual machine is stopped and the virtual disk is not
being accessed with any other tool)?

My secondary question is why the qcow2 specification (qcow2.txt)
is not installed with the other documentation files, and why there
is no corresponding web page (not even in the qemu Wiki)?

Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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