tested on host

# debian 10

this option is only available in the gui on newer versions of virsh-manager

to create a thin provisioned harddisk of capacity of 32GB image via bash-terminal go:

qemu-img create -f qcow2 name-of-harddisk-image.qcow2 32G

as in VirtualBox, is it possible to create bigger virtual harddisks on smaller physical harddisks, by think provisioning qcow2 format (kvm default)

but per default, virt-manager says “can not create such disk files”… but it can:

Created with GIMP

# real disk size
du -hs /home/user/vms/debian10

# maximum allowed disk size
ls -lah /home/user/vms/debian10
-rw------- 1 libvirt-qemu libvirt-qemu 513G Aug  1 14:05 /home/user/vms/debian10