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Kernelbased Virtual Machine (KVM)

CPU support

You need to find out if your CPU has virtualization support and whether it is turned on. Support may be turned off in your BIOS. Running the command below appropriate for your CPU manufacturer will produce output if KVM support is found:

 egrep '^flags.*(vmx|svm)' /proc/cpuinfo

Install

 sudo apt-get install kvm python-vm-builder 

Networking

 auto lo
 iface lo inet loopback
 
 auto eth0
 iface eth0 inet manual
 
 auto br0
 iface br0 inet static
        address 192.168.0.10
        network 192.168.0.0
        netmask 255.255.255.0
        broadcast 192.168.0.255
        gateway 192.168.0.1
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0
        bridge_maxwait 0

Create a KVM image

Create a directory that will contain the kvm images

 mkdir /var/kvm_images
 cd /var/kvm_images

Create a file named 'partfile' with the partitions we want (a new disk starts on a line with '---'):

 root 2000
 swap 512
 /tmp 512
 ---
 /home 10000

Create a file 'kvm-template' with you params.

 vmbuilder kvm ubuntu \
                  --suite lucid \
                  --flavour virtual \
                  --domain kvm01 \
                  --dest kvm01 \
                  --arch i386 \
                  --hostname kvm01.filmer.nl \
                  --mem 512 \
                  --user andries \
                  --pass mypass \
                  --ip 194.242.19.101 \
                  --mask 255.255.255.0 \
                  --net 194.242.19.0 \
                  --bcast 194.242.19.255 \
                  --gw 194.242.18.1 \
                  --dns 194.242.18.194 \
                  --mirror http://nl.archive.ubuntu.com/ubuntu \
                  --components main,universe,restricted \
                  --addpkg openssh-server \
                  --addpkg vim \
                  --addpkg language-pack-en \
                  --addpkg language-pack-nl \
                  --part /var/kvm_images/kvm/kvm-partfile \
                  --verbose;

If you want to use libvirt add this line to.

                  --libvirt qemu:///system ;

Create a kvm.

 sh < kvm-template

Start KVM on server

First check if the /etc/kvm/kvm-ifup_br0 exists.

 #!/bin/sh
 
 sudo /sbin/ifconfig $1 0.0.0.0 up
 sudo /usr/sbin/brctl addif br0 $1
 exit 0

Start command (Remerber to change the name,file,tap,macaddr,vnc:port) for each virtual machine.

 /usr/bin/kvm \
 -M pc \
 -m 512 \
 -smp 1 \
 -name vm01.filmer.nl \
 -monitor pty \
 -drive file=/var/kvm_images/vm01/disk0.qcow2,if=ide,index=0,boot=on \
 -drive file=/var/kvm_images/vm01/disk1.qcow2,if=ide,index=1 \
 -net nic,vlan=0,macaddr=52:54:00:99:00:01 \
 -net tap,vlan=0,ifname=tap101_br0,script=/etc/kvm/kvm-ifup_br0 \
 -vnc 127.0.0.1:1;

Connect to your remote KVM with VNC

 sudo apt-get install vncviewer

By default KVM also starts a VNC server on 127.0.0.1. An SSH tunnel can be used to connect to this VNC server safely (encrypted). Give this command on your local system (your desktop PC) to the kvm-host server.

 ssh -L 5900:127.0.0.1:5900 kvm-host.filmer.nl 

After logging in you can connect to 127.0.0.1:5900 with VNC viewer.
use vnc:port +5900 from the start command io 5901 for vm01

VNC and MS windows

Make al local connection to the server with the windows kvm image.

 ssh -L 5900:127.0.0.1:5900 kvm-host.filmer.nl

Start the kvm image on de host without a network, it creates a NAT network bij default.

 /usr/bin/kvm -M pc -m 1024 -smp 1 -monitor pty -drive file=/var/kvm_images/vista/vista-1.img,if=ide,boot=on -usb -vnc 127.0.0.1

Connect with terminal server to localhost:5900

VNC mouse pointer cap

The vncserver included in qemu has a irritating drawback. There's a gap between the real mouse pointer and the vnc mouse pointer. You can use the "-usbdevice tablet" option to avoid this unpleasant effect.

Resize qemu image

On the host stop the KVM guest. Copy the qcow2 image into a raw image:

 cd /var/kvm_images/<kvm_name>
 qemu-img convert root.qcow2 -O raw root.raw

The raw image can be grown to the desired size (in the example 16GB)

 dd bs=1 if=/dev/zero of=root.raw seek=16G count=0

Now we have increased the image size, but the partitions are still the old small size. The easiest way to resize the partitions is by using the GParted live CD. Download the [http://gparted.sourceforge.net/livecd.php iso image] and start KVM with the CD image and the disk image, booting from CD:

 /usr/bin/kvm -M pc -m 1536 -monitor pty -no-acpi -cdrom /root/gparted-live-0.3.9-4.iso \
 -drive file=/var/kvm_images/webserver.customer/root.raw,if=ide -usb -usbdevice tablet -vnc 192.168.2.230:0 -boot d

Now start the KVM guest and resize the partitions using GParted. If you add partitions don't forget to change /etc/fstab on the disk. To do so you will need to look up the UUID of the new partition:

 vol_id -u device

When finished stop the KVM client. Backup the unchanged qcow2 image and convert the raw image to the new qcow2 image

 mv root.qcow2 root.qcow2.bak
 qemu-img convert root.raw -O qcow2 root.qcow2

libvirt has to be restarted, otherwise the new kvm won't load (which is a bit strange, by the way).

 /etc/init.d/libvirt-bin restart

Maybe this is also enough, but test it first:

 /etc/init.d/libvirt-bin reload

The new KVM image can now be started with virsh.

Mount partition inside qemu image

Create the devices /dev/ndb*

 modprobe nbd max_part=8
 kvm-nbd -c /dev/nbd0 /path/to/image
 mount /dev/nbd0p1 /mnt
 umount /mnt
 kvm-nbd -d /dev/nbd0

Now you also fdisk

 modprobe nbd max_part=8
 kvm-nbd -c /dev/nbd0 /path/to/image
 fdisk /dev/nbd0p1 

Start KVM from a liveCD

You may want to start KVM from a liveCD when you messed up the network and cannot login. Use a command like:

 /usr/bin/kvm -M pc -m 1536 -smp 1 -monitor pty -no-acpi -cdrom /root/gparted-live-0.3.9-4.iso \
 -drive file=/var/kvm_images/webserver.customer/root.qcow2,if=ide -net nic,macaddr=52:54:00:44:a8:80,vlan=0,model=virtio \
 -net tap,fd=8,script=,vlan=0 -usb -vnc 192.168.2.230:0 -boot d

Replace the macaddr with the 'real' mac address of the kvm, to be safe.

Create a KVM from a template image

When creating a KVM from an existing image don't forget these steps:

• Mount the root image on /mnt (see above)
• Change IP address(es) in /mnt/etc/network/interfaces
• Change the hostname in /mnt/etc/hostname and /etc/hosts
• Create new ssh keys

 ssh-keygen -f /mnt/etc/ssh/ssh_host_rsa_key -N '' -t rsa
 ssh-keygen -f /mnt/etc/ssh/ssh_host_dsa_key -N '' -t dsa

iptables

With public ipaddressen and bridging I test with: (not finished yet)

 iptables -A FORWARD -i anywhere -o anywhere -j ACCEPT

Resources

• https://help.ubuntu.com/community/KVM/
• https://help.ubuntu.com/community/JeOSVMBuilder
• http://virt-tools.org/learning/

Keep watching these...

• Sheepdog project Distributed Storage Management for qemu/kvm
• Open Nebula
• Open Stack
• Ganeti
• Convirt is a centralized management solution that lets you manage the complete lifecycle of your KVM deployments.

Configuratiebeheertools

• http://www.opscode.com/chef/
• http://www.cfengine.org/
• http://www.puppetlabs.com/puppet/introduction/

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