On Wed, Sep 06, 2017 at 01:38:45PM +0200, Kevin Wolf wrote: > This command line fragment looks correct to me. For me, it seems to > work. I'm starting a first qemu in the background with default locking > options: > > $ x86_64-softmmu/qemu-system-x86_64 -hda /tmp/test.qcow2 > > And then starting a second one with a command line resembling yours: > > $ x86_64-softmmu/qemu-system-x86_64 -device virtio-scsi \ > -drive > file=/tmp/test.qcow2,cache=unsafe,format=qcow2,file.locking=off,id=hd0,if=none > \ > -device scsi-hd,drive=hd0
The problem is with overlays, where file.locking doesn't propagate to the backing file. Thus: $ qemu-system-x86_64 -drive file=backing,format=raw while in another terminal: $ qemu-img create -b backing -f qcow2 overlay $ qemu-system-x86_64 -drive file=overlay,format=qcow2,file.locking=off qemu-system-x86_64: Failed to get shared "write" lock Is another process using the image? After some experimentation, I came up with this command which works: $ qemu-system-x86_64 -drive file.file.filename=overlay,file.driver=qcow2,file.backing.file.locking=off Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
