hi,all please tell me the defferences between two commands of the following two groups. my test vm is http://wiki.qemu.org/download/linux-0.2.img.bz2 qemu is qemu-kvm-0.12.1.2-2.415.el6_5.10.x86_64 kernel is 2.6.32-279.el6.x86_64, centos 6.3 ---------------------------------------------------------------------------------------------------- /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -drive format=raw,file=/root/linux-0.2.img,if=ide /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -drive format=raw,file=/root/linux-0.2.img,if=none,id=drive-virtio-disk0 -device ide-drive,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 the first one , i set if=ide . the second, i relate drive with device which is ide-drive. i think they should have the same effect, but the latter command can not work, vm panic. if i set 'bus=ide.0,unit=0', it works. do we have to assign slot for device manually? qemu does not handle it? ----------------------------------------------------------------------------------------------------- /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -nodefconfig -nodefaults -drive format=raw,file=/root/linux-0.2.img,if=ide /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -drive format=raw,file=/root/linux-0.2.img,if=ide the first one use default config, the vm panics. what is default config ? how default config affects vm? -------------------------------------------------------------------------------------------------- /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -drive format=raw,file=/root/linux-0.2.img,if=none,id=drive-virtio-disk0 -device ide-drive,bus=ide.0,unit=0,drive=drive-virtio-disk0,id=ide-disk0,bootindex=1 /usr/libexec/qemu-kvm -enable-kvm -m 64 -M rhel6.5.0 -vnc 0.0.0.0:1 -drive format=raw,file=/root/linux-0.2.img,if=none,id=drive-virtio-disk0 -device virtio-blk-pci,scsi=off,bus=pci.0,drive=drive-virtio-disk0,id=ide-disk0,bootindex=1 why changing driver affects vm? to my knowledge, i think it is ok to change device's driver. thanks.