Virtualization in Grid'5000

See also: KVM | KVM contextualization | KVM multi-site | KVM on production environment

Purpose

This page presents ways to use KVM on production image. The aim is to permit the execution of virtual machines on the nodes with a "non-deploy" reservation.

First steps

Job submission

In order to test easily the kvm environment, we will use an interactive job.

frontend:

oarsub -I

	Note
	- Some clusters don't have virtualization support in the BIOS. You can check if a node supports virtualization with the following command: node: egrep '^flags.*(vmx|svm)' /proc/cpuinfo - You can request nodes with enabled virtualization support, using the "virtual" property: frontend: oarsub -I -p "virtual != 'none'"

Disk image, virtual machine

A disk image containing debian squeeze is available at the following path: /grid5000/images/KVM/squeeze-x64-base.qcow2

It can be use as a base for more advanced work. For the next steps of this tutorial, copy the disk image to /tmp on the node

node:

cp /grid5000/images/KVM/squeeze-x64-base.qcow2 /tmp/

Network configuration

In order to use the network with kvm, a Tun/Tap interface must be created for each virtual machines. This virtual interface will be attached to your virtual machine, and bridged on the production network. Therefore, the virtual machine will be able to get an IP from the DHCP server and access the network.

A script is available to create automatically this interface on the node: create_tap:

node:

sudo create_tap

• Tun/Tap interfaces are listed by issuing the command /sbin/ifconfig.

node:

/sbin/ifconfig

tap0      Link encap:Ethernet  HWaddr 00:16:3e:db:c6:41
          inet6 addr: fe80::58ff:a4ff:fe97:c6a8/64 Scope:Link
          UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:29435 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

	Note
	- Create one Tun/Tap interface per guest OS. - Use tunctl if you need to delete a Tun/Tap device. node: /usr/sbin/tunctl -d tap0

Generate a random mac address

• Use the following script random_mac. This will generate a random mac address, starting with 00:16:3e, which will be attributed in the next step to the virtual machine.

node:

export MACADDR=`random_mac`

	Note
	The first three bytes are important (identification for the virtualized network). Do not change it.

Run the guest OS using the kvm command

Start the virtual machine with the kvm command. The following command is just an example, feel free to adapt it to your use case. The kvm process in launched a screen session, if you are not familiar with screen, read its documentation.

node:

screen kvm -m 512 -hda /tmp/squeeze-x64-base.qcow2 -net nic,model=virtio,macaddr=$MACADDR -net tap,ifname=tap0,script=no -nographic

	Note
	- tap0 is the name of our Tun/Tap interface. Adapt it with the Tun/Tap name on witch you want to attach your guest OS. - The variable $MACADDR contains the previously generated mac address. - The password for the root account is grid5000

Or, use libvirt

Libvirt is a toolkit for managing virtualization servers. Libvirt is also an abstraction layer for different virtualization solutions, including KVM but also Xen and VMWare ESX. In our case, we use libvirt on top of KVM.

• Create a domain file in XML, describing a virtual machine. Don't forget to adapt this example to your case (especially, replace the mac address by a randomly generated one).

eg : domain.xml

 <domain type='kvm'>
  <name>squeeze</name>
  <memory>524288</memory>
  <vcpu>1</vcpu>
  <os>
    <type arch="x86_64">hvm</type>
  </os>
  <clock sync="localtime"/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <driver type='qcow2'/>
      <source file='/tmp/squeeze-x64-base.qcow2'/>
      <target dev='vda' bus='virtio'/>
     <shareable/>
    </disk>
    <interface type='ethernet'>
      <target dev='tap0'/>
      <script path='no'/>
      <model type='virtio'/>
      <mac address='00:16:3e:78:b8:04'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/ttyS0'/>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <source path='/dev/ttyS0'/>
      <target port='0'/>
    </console>
  </devices>
 </domain>

• Now, the guest OS can be started.

node:

virsh create domain.xml

• You can also use virsh to manage your guest OS:
  • list the running virtual machines: virsh list
  • open a console on the "squeeze" virtual machine: virsh console squeeze

	Note
	- You can use the script /usr/local/bin/random_mac to generate a mac address. - Use CTRL+AltGr+] to disconnect from virsh console

Misc notes

• Read KVM contextualization, if you want to perform some customization for your VMs, like using static addresses in conjunction with a subnet reservation.
• For the deployment of an important number of guest OS, you can use the subnet reservation. See also the virtual network interlink.