I have just configured a debian 7.8 server with KVM and tried to preallocate a disk image with the following command:qemu-img create -f qcow2 -o preallocation=metadata,lazy_refcounts=on /home/stuart/vms/ubuntu.base.img 20GThis results in the following error:Unknown option 'lazy_refcounts'qemu-img: Invalid options for file format 'qcow2'.Now when I run that command on an Ubuntu 14.04 KVM hypervisor, it works just fine, so I am guessing that my Qemu version is too old? The output of qemu -version is:QEMU emulator version 1.1.2 (Debian 1.1.2+dfsg-6a+deb7u6), Copyright (c) 2003-2008 Fabrice BellardQuestion:Do I need a later version of qemu to be able to take advantage of lazy refcounts, and if so does anybody know how I can grab a stable later version? Perhaps the command just needs to be written differently for debian?
Debian - qcow2 lazy_refcounts
debian;kvm
Lazy refcounts were added in version 1.2, so the version you have is indeed too old to support that feature.You can install a newer version from Debian backports.