1. Virtualization with qemu-kvm

2. Understading qemu-kvm

3. Creating VM with virtual interface TAP

4. Creating Linux Bridges with virtual interface TAP

ATTENTION: Replace where yourlogin by uXXXvnet

1. Virtualization with qemu-kvm

 1. Virtualization with qemu-kvm.
 How was enabled ?
First you do have a flag in your CPU:
$ egrep "(vmx|svm)" /proc/cpuinfo

Second you do need enable the module kernel:

modprobe kvm
modprobe kvm_intel ou kvm_amd

To see:
$ lsmod | grep kvm

More about: http://wiki.qemu.org/KVM

2. Understading qemu-kvm.

The qemu-kvm has 3 output:
* Export to your display and/or send to VNC/Spice.
$ qemu-kvm -vnc :0

but in our lab we are going to use display none.
$ qemu-kvm -display none

- Monitor of your virtual machine.
$ qemu-kvm -monitor stdio -display none

(qemu) info kvm
...
(qemu) info status
...
(qemu) stop
(qemu) info status
...
(qemu) quit

More monitor commands: https://en.wikibooks.org/wiki/QEMU/Monitor

We can add this monitor in socket TCP.
$ qemu-kvm -chardev socket,id=tcpmon0,port=5000,host=localhost,server,nowait -monitor chardev=tcpmon0 &

* Replace the number port 5000 for your number port 5XXX

To access the monitor in socket TCP.
$ nc localhost
(qemu) quit

Copy disk to your VM
$ cp /vms/vm.img disk-vm.img

And start it with 128MB memory, disk disk-vm.img and serial default output.
$ qemu-kvm -m 128 \
-drive file=disk-vm.img \
-serial stdio \
-display none

Waiting your machine start.

Login in your VM with user and password:
cirros login: cirros
passord: cubswin:)
$ free -m
$ sudo poweroff


3. Creating VM with virtual interface TAP.


a ) Create interface TAP
$ sudo ip tuntap add yourlogin-tap0 mode tap

b ) Enable the interface
$ sudo ip link set yourlogin-tap0 up

c ) Setting a static IP address in your interface tap
$ sudo ip addr add 192.168.10.1/24 dev yourlogin-tap0

To verify the IP address configuration of yourlogin-tap0, you can use the ifconfig command in the following manner.

$ ifconfig yourlogin-tap0

d ) Copy the disk for your VM
$ cp /vms/vm.img .

e ) Start your VM with qemu-kvm
$ qemu-kvm -m 128 -drive file=vm.img \
          -netdev type=tap,ifname=yourlogin-tap0,id=net0,script=no \
          -device virtio-net-pci,netdev=net0,mac=aa:00:00:11:76:f0 \
          -serial stdio -display none

* You are waiting your VM begin.

f ) After your VM start. You are going to need login.
user: cirros
password: cubswin:)

e ) Now you are setting a static IP address on interface eth0 of VM
$ sudo ip link set eth0 up
$ sudo ip addr add 192.168.10.2/24 dev eth0

To verify the connection between VM and Host with interface yourlogin-tap0
$ ping -c 5 192.168.10.1

** Now you can shutdown your VM: $ sudo poweroff

4. Creating Linux Bridges with virtual interface TAP.
a ) Create 2 interfaces TAP, being a for VM1 and another to VM2.
$ sudo ip tuntap add yourlogin-vm1-tap mode tap
$ sudo ip tuntap add yourlogin-vm2-tap mode tap

b ) Now we should start the interfaces.
$ sudo ip link set yourlogin-vm1-tap up
$ sudo ip link set yourlogin-vm2-tap up

c ) For to create a bridge Linux and include the interface it.
$ sudo brctl addbr yourlogin-br0
$ sudo brctl addif yourlogin-br0 yourlogin-vm1-tap
$ sudo brctl addif yourlogin-br0 yourlogin-vm2-tap

d ) Now we should start the bridge.
$ sudo ip link set yourlogin-br0 up

e ) For to show the bridge, use the command
$ sudo brctl show

f ) Now you can enable two SSH session and start in each VM with your interface.

* Session 1
$ cp /vms/vm.img vm1.img
$ qemu-kvm -m 128 -drive file=vm1.img \
          -netdev type=tap,ifname=yourlogin-vm1-tap,id=net0,script=no \
          -device virtio-net-pci,netdev=net0,mac=aa:00:00:11:76:f1 \
          -serial stdio -display none

* Session 2
$ cp /vms/vm.img vm2.img
$ qemu-kvm -m 128 -drive file=vm2.img \
          -netdev type=tap,ifname=yourlogin-vm2-tap,id=net0,script=no \
          -device virtio-net-pci,netdev=net0,mac=aa:00:00:11:76:f2 \
          -serial stdio -display none

g ) Set the IP address in each of the VMs.

* Session 1

user: cirros
password: cubswin:)

$ sudo ip link set eth0 up
$ sudo ip addr add 10.2.3.1/24 dev eth0

* Session 2
user: cirros
password: cubswin:)

$ sudo ip link set eth0 up
$ sudo ip addr add 10.2.3.2/24 dev eth0

h ) To test you can use the command PING

* Session 1
$ ping -c 5 10.2.3.2