Hi, On a fresh FC12 system, I am able to create and run KVM-based vms with tap networking using the qemu-kvm command line but not using virsh. I have user and group set to "root" in /etc/libvirt/qemu.conf. "user mode networking" works with virsh, but not tap! I have this xml: <domain type='kvm'> <name>centos</name> <uuid>22d9d573-d82c-c18d-36c0-d3ffef057468</uuid> <memory>131072</memory> <vcpu>1</vcpu> <os> <type arch='x86_64'>hvm</type> </os> <features> <acpi/> <pae/> </features> <clock offset='utc'/> <devices> <emulator>/usr/bin/qemu-kvm</emulator> <disk type='file' device='disk'> <source file='/var/lib/images/centos.5-4.x86-64/centos-small.img'/> <target dev='hda' bus='ide'/> </disk> <interface type='user'> <mac address='52:54:00:7e:5b:58'/> </interface> <interface type='ethernet'> <mac address='52:54:00:2e:33:c8'/> <script path='/var/lib/images/centos.5-4.x86-64/qemu-ifup'/> </interface> <graphics type='vnc' port='5910' autoport='no' listen=''/> </devices> </domain> This won't start even when I execute virsh as root: [root@fc12 centos.5-4.x86-64]# virsh -c qemu+unix:///system create domr.xml error: Failed to create domain from domr.xml error: monitor socket did not show up.: No such file or directory [root@fc12 centos.5-4.x86-64]# tail -3 /var/log/libvirt/qemu/centos.log LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none /usr/bin/qemu-kvm -S -M pc-0.11 -m 128 -smp 1 -name centos -uuid 22d9d573-d82c-c18d-36c0-d3ffef057468 -monitor unix:/var/lib/libvirt/qemu/centos.monitor,server,nowait -boot c -drive file=/var/lib/images/centos.5-4.x86-64/centos-small.img,if=ide,index=0,boot=on -net nic,macaddr=52:54:00:7e:5b:58,vlan=0,name=nic.0 -net user,vlan=0,name=user.0 -net nic,macaddr=52:54:00:2e:33:c8,vlan=1,name=nic.1 -net tap,script=/var/lib/images/centos.5-4.x86-64/qemu-ifup,vlan=1,name=tap.0 -serial none -parallel none -usb -vnc :10 -vga cirrus warning: could not configure /dev/net/tun: no virtual network emulation qemu: Could not initialize device 'tap' '***** But I can execute the same command line and it works!!******** [root@fc12 centos.5-4.x86-64]# LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none /usr/bin/qemu-kvm -S -M pc-0.11 -m 128 -smp 1 -name centos -uuid 22d9d573-d82c-c18d-36c0-d3ffef057468 -monitor unix:/var/lib/libvirt/qemu/centos.monitor,server,nowait -boot c -drive file=/var/lib/images/centos.5-4.x86-64/centos-small.img,if=ide,index=0,boot=on -net nic,macaddr=52:54:00:7e:5b:58,vlan=0,name=nic.0 -net user,vlan=0,name=user.0 -net nic,macaddr=52:54:00:2e:33:c8,vlan=1,name=nic.1 -net tap,script=/var/lib/images/centos.5-4.x86-64/qemu-ifup,vlan=1,name=tap.0 -serial none -parallel none -usb -vnc :10 -vga cirrus & [2] 4543 [root@fc12 centos.5-4.x86-64]# ps -ef | grep qemu root 4543 3449 0 19:02 pts/12 00:00:00 /usr/bin/qemu-kvm -S -M pc-0.11 -m 128 -smp 1 -name centos -uuid 22d9d573-d82c-c18d-36c0-d3ffef057468 -monitor unix:/var/lib/libvirt/qemu/centos.monitor,server,nowait -boot c -drive file=/var/lib/images/centos.5-4.x86-64/centos-small.img,if=ide,index=0,boot=on -net nic,macaddr=52:54:00:7e:5b:58,vlan=0,name=nic.0 -net user,vlan=0,name=user.0 -net nic,macaddr=52:54:00:2e:33:c8,vlan=1,name=nic.1 -net tap,script=/var/lib/images/centos.5-4.x86-64/qemu-ifup,vlan=1,name=tap.0 -serial none -parallel none -usb -vnc :10 -vga cirrus