How to mount and eject a CD-rom on a Windows Xen guest
Originally, it was possible to access the QEMU console from within a VNC viewer window, by pressing Ctrl-Alt-1. Since this made for a major security breach – users are able to mount any file on Dom0 this way, the feature has been disabled in recent Xen releases. That makes for a major problem, since mounting, ejecting and changing CD’s in Windows seems only possible by rebooting the Virtual Machine.
After a bit of trial and error, we came to a solution that allows the mounting and ejecting of CD’s from within Windows:
In your Xen guest config file, you must specify an empty CD device – since without it Windows will fail to recognize a CD-rom device:
Mounting a CD-rom
Execute xm block-list to view the configured bloack devices for your Xen guest:
(768
((backend-id 0)
(virtual-device 768)
(device-type disk)
(state 1)
(backend /local/domain/0/backend/vbd/1/768)
)
)
(5632
((backend-id 0)
(virtual-device 5632)
(device-type cdrom)
(state 1)
(backend /local/domain/0/backend/vbd/1/5632)
)
)
Note the cdrom’s device number and detach it from the guest. Use the –force switch, else detaching will fail.
Now reattach the device with the correct path specified ( phy:/dev/cdrom, file:/path/to/some/iso, … ):
Unmounting a CD-rom
Eject the cdrom from Windows by right-clicking on its icon and selecting ‘Eject’.
Eject the cdrom physically from Dom0 if needed:
Remounting a CD-rom
Now’s the fun part: it appears that if you try to remount exactly the same backend device, e.g. /dev/cdrom, the Windows HVM guest will not be signalled that a new device has been inserted. A workaround for this is to attach and to detach another device first – any will do, as long as it’s different:
# xm block-detach 1 5632 -f
Then attach your new device:
