Back up or move a box
Two components are required to back up or move a box: the image file, and the configuration of the box saved as an XML file. Saving the configuration requires the virsh command from the libvirt or libvirt-client package.
In a terminal window, type
virsh dumpxml Name > Name.xml
where Name is the Boxes name, or domain, of your box. To list the domains seen by Boxes, type
virsh -c qemu:///session list --all
Copy the .xml file you just created to your backup or temporary storage location.
Copy the image file to your backup or temporary storage location. It will be a file with the domain name of your box and ending in .qcow2, located in ~/.local/share/gnome-boxes/images/.