Given the scenario where the disks of a virtual server are defined in the following order
harddisk hda harddisk vda cdrom vdb cdrom hdb
From the above links, I'm guessing that hdb will be boot attempted. Is this
Boot device type is crdom. Which cdrom device will be boot attempted? the actual behavior?
That depends on BIOS implementation used by qemu and to be honest, I'm not sure what the default behavior is; you would need to try that :-) However, if you have new enough libvirt (>= 0.8.8), qemu and SeaBIOS (AFAIK qemu >= 0.14.0 should be ok), you can better control boot order by using per-device boot configuration. That is, instead of specifying <os> ... <boot dev='cdrom'/> </os> you would use something like <devices> ... <disk type='file' device='cdrom'> ... <boot order='1'/> </disk> </devices> It's also documented in libvirt XML documentation at http://www.libvirt.org/formatdomain.html#elementsDisks Jirka