On Thu, Jul 13, 2017 at 05:04:07PM +0800, 陳培泓 wrote: No, guestfs_compress_out is nothing to do with qcow2 compression. The only way to create a qcow2 compressed filesystem is ‘qemu-img convert ... -c -O qcow2 ...’ The qcow2 format does not support incrementally writing compressed clusters, and so it's not something which libguestfs can do unless qemu's qcow2 block driver changes in future. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org