I have a problem with libvirt and serial ports. When I run a xml with serial tag over libvirt0.8.0 and qemu 0.11 this is the line that libvirt execute LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin QEMU_AUDIO_DRV=none /usr/bin/kvm -S -M pc-0.11 -cpu qemu32 -enable-kvm -m 0 -smp 1 -name uml2 -uuid 431cb9f4-fdba-c4e8-a35f-23b52f91120a -monitor unix:/var/lib/libvirt/qemu/uml2.monitor,server,nowait -boot cd -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/root_cow_fs,if=ide,bus=0,unit=0,boot=on -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/opt_fs.iso,if=ide,media=cdrom,bus=0,unit=1 -net nic,macaddr=fe:fd:00:00:02:01,vlan=0,name=net0 -net tap,fd=19,vlan=0,name=hostnet0* -serial unix:/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/uml2_socket,server,nowait * -parallel none -usb -vnc :1001 -vga cirrus -balloon virtio and the virtual machine created have a serial port but when I run the same xml in a machine with qemu 0.12.3 this is the line that libvirt execute LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin QEMU_AUDIO_DRV=none /usr/bin/kvm -S -M pc-0.12 -cpu qemu32 -enable-kvm -m 0 -smp 1,sockets=1,cores=1,threads=1 -name uml2 -uuid 3e3a4836-94b4-869c-4180-724c970c1909 -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/uml2.monitor,server,nowait -mon chardev=monitor,mode=readline -rtc base=utc -boot cd -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/root_cow_fs,if=none,id=drive-ide0-0-0,boot=on -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/opt_fs.iso,if=none,media=cdrom,id=drive-ide0-0-1,readonly=on -device ide-drive,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1 -device rtl8139,vlan=0,id=net0,mac=fe:fd:00:00:02:01,bus=pci.0,addr=0x4 -net tap,fd=18,vlan=0,name=hostnet0 -chardev socket,id=serial0,path=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/uml2_socket,server,nowait -device isa-serial,chardev=serial0 -usb -vnc :1001 -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 the virtual machine don't have any serial port. If you execute the line: /usr/bin/kvm -M pc-0.11 -cpu qemu32 -enable-kvm -m 0 -smp 1 -name uml2 -uuid 431cb9f4-fdba-c4e8-a35f-23b52f91120a -monitor unix:/var/lib/libvirt/qemu/uml2.monitor,server,nowait -boot cd -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/root_cow_fs,if=ide,bus=0,unit=0,boot=on -drive file=/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/fs/opt_fs.iso,if=ide,media=cdrom,bus=0,unit=1 -net nic,macaddr=fe:fd:00:00:02:01,vlan=0,name=net0 -net tap,fd=19,vlan=0,name=hostnet0* -serial unix:/root/.vnuml/simulations/tutorial-r1_xp/vms/uml2/uml2_socket,server,nowait * -parallel none -usb -vnc :1001 -vga cirrus -balloon virtio (the same line before) over qemu 0.12.3 the viertual machine have serial port. Any ideas?