KVM

# Add a tun interface
    tunctl -t tap0 -u root
# Add a bridge
    brctl addbr br0
    brctl addif br0 tap0
    ip a a 10.0.0.1/24 brd + dev br0
# Create disk image
    qemu-img create -f qcow2 winxp.img 3G
# Install an OS
    kvm -m 4096 -vnc '127.0.0.1:1' -cdrom /home/winxp.iso -boot d win2008r2 -net nic,vlan=1,macaddr=00:aa:00:60:00:01,model=e1000 -net tap,vlan=1,ifname=tap0,script=no
# Launch KVM
    kvm -rtc base=localtime -smp 4 -m 8192 -vnc '127.0.0.1:1' -boot c foobar.raw -net nic,vlan=1,macaddr=00:aa:00:60:00:01,model=e1000 -net tap,vlan=1,ifname=tap1,script=no
# Forward a port
    iptables -t nat -A PREROUTING -p tcp -i eth0 -d <real ip> --dport 3389 --sport 1024:65535 -j DNAT --to 10.0.0.2:5900
    sysctl net.ipv4.ip_forward=1
# Allow VM to the Internet
    iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE -s 10.0.0.2

# Connect to QEMU monitor
     socat - /var/run/qemu-server/foo.mon
 
# Forward a port usign kvm
    # In the monitor...
         hostfwd_add tcp::2201-:22
         info usernet
    # ...Or just from the console
         echo hostfwd_add tcp::2203-:22 | socat - /var/run/qemu-server/103.mon
 
# Map a loop device to the image file
     losetup -f
     losetup /dev/loop0 foo.img
     kpartx -av /dev/loop0
     ls -alF /dev/mapper
     mount /dev/mapper/loop0p1 /mnt/debianvm
     unmount /mnt/debianvm
     kpartx -dv /dev/loop0
     losetup -d /dev/loop0
 
# Hot add disk image
     # in quemu monitor
         socat - /var/run/qemu-server/101.mon
         pci_add auto storage file=/srv/foo.img,if=virtio
         drive_del virtio0
     # in guest system
         modprobe acpiphp
         modprobe pci_hotplug