[Qemu-discuss] Is it possible to write to a QEMU CDROM device?

[Steve Ross]

Hello all,

I'm a new-comer to the list (and my apologies if this is not the appropriate place to ask my question).

My goal is to write from the guest OS to a CD or DVD reader/writer on my host system.  Currently, the write operation is failing.  I believe it is because the virtual CD-ROM device is set to be "readonly".  Is it possible to write to a QEMU CDROM device and, if so, how?

I'm using the "virt-manager" GUI to start the virtual machine.  Once started, the "qemu" command line from my virtual machine process includes the following, where the host's built-in CD reader/writer is "/dev/sr0".

/usr/bin/qemu-system-x86_64 ... -drive file=/dev/sr0,if=none,id=drive-ide0-0-1,readonly=on,format=raw

This obviously says that the device is "readonly".

A snippet of XML from my virtual machine from the CDROM is:

<domain type='kvm'>
...
  <devices>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/sr0'/>
      <target dev='hdb' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>


I've tried removing the <readonly/> tag from the above VM definition, and then running the VM, but the tag magically reappears in the VM definition when it runs.

Also, the "virt-manager" GUI shows the CDROM device as having the option of "Readonly" being checked (and the GUI does not allow me to uncheck it.)

Other details:

• qemu version 2.1.3 on Fedora 21.
• libvirt version 1.2.0.2
  

Thanks for any help or pointers you can provide,
-- Steve