Installing KVM & OVS on Ubuntu
KVM & OpenvSwitch are technologies I’ve wanted to learn for a while now. I think it’ll really help my understanding and knowledge of Linux and the underlying mechanics of virtualisation and how it interacts with the physical network.
Installing KVM is already well documented here, but for completeness here is my installation process:
First, update, and check your hardware can support virtualisation.
$ sudo apt-get -y update $ egrep -c '(vmx|svm)' /proc/cpuinfo 8 $ kvm-ok INFO: /dev/kvm exists KVM acceleration can be used
egrep is like
grep, a command that prints out any line with the given regular expression. So, here we’re searching the cpuinfo file for any lines containing vmx or svm. vmx is the flag that virtualisation is enabled in the BIOS for Intel CPUs & svm is the same for AMD CPUs. The
-c option is for count, so here we only print out the number of lines that match, rather than the lines themselves.
So, a result of 1 or more means virtualisation is enabled. Here, I’ve got 8 lines in the cpuinfo file matching vmx.
If you do get a 0, reboot your computer, go into the BIOS menu and make sure you’ve got virtualisation enabled.
kvm-ok program verifies whether your machine is able to run KVM virtual machines. It actually checks the cpuinfo file, like we did in the previous command. It also checks whether the kernel has detected the CPUs Virtualisation Technology (VT) capability, and looks to see if
The capabilities exist, so let’s install KVM.
$ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils virtinst
From the Ubuntu pages:
- libvirt-bin provides libvirtd which you need to administer qemu and kvm instances using libvirt
- qemu-kvm is the backend
- ubuntu-vm-builder powerful command line tool for building virtual machines
- bridge-utils provides a bridge from your network to the virtual machines
- virtinst provides an easy way to provision operating systems into virtual machines and an API to the virt-manager application for its graphical VM creation wizard.
Ensure the user is added to the
$ sudo adduser `id -un` libvirtd && sudo adduser `id -un` kvm The user `rob' is already a member of `libvirtd'. The user `rob' is already a member of `kvm'.
I found it was good to do a reboot here, just to make sure this membership is in effect.
Verify the installation. When we get round to installing some VMs, they should show up in this list.
$ virsh -c qemu:///system list Id Name State ----------------------------------------------------
And we’re all set.
On a separate machine, I’ve set up a Xubuntu VM, and installed Virtual Machine Manager (VMM), just to give me a visual understanding of my VMs if need be.
$ sudo apt-get install virt-manager
VMM is super simple and intuitive. I love using the command line, but I still find having visual cues really helps my understanding of a situation, too much time in Windows & vSphere perhaps!
For the OpenvSwitch installation I pretty faithfully followed Scott Lowe’s example, with a couple of differences.
Right, let’s get up-to-date, as per.
$ sudo apt-get -y update && sudo apt-get -y dist-upgrade
Make way for OVS by removing the default libvirt bridge.
$ sudo virsh net-destroy default $ sudo virsh net-autostart --disable default
Remove ebtables, a Linux ethernet firewall.
$ sudo aptitude purge ebtables
$ sudo apt-get install openvswitch-controller openvswitch-switch openvswitch-datapath-source
openvswitch-brcompat has apparently been removed now from OVS, so it can be ignored.
Once that’s finished, try starting OVS, though I found it was already running.
$ sudo service openvswitch-switch start start: Job is already running: openvswitch-switch
Run the OVS show command, you should just get an empty config.
$ sudo ovs-vsctl show 7d84d624-632b-4d2c-93ad-56ad3cc543cc ovs_version: "2.0.2"
ovs-vsctl command, according to the man page, is a “utility for querying and configuring ovs-vswitchd”.
ovs-vswitchd is, again according to the man page, the daemon that manages and controls the OVS switch(es). As far as I understand it
ovs-vsctl queries and configures
ovsdb-server (which provides the interface to the OVS databases [man page] ), and
ovs-vswitchd then implements the changes. To be honest I’m not entirely sure of this process, I need to spend some more time reading this I think.
ovs-vsctl show “Prints a brief overview of the database contents.” Of which, currently, we have none.
Now, the OVS bridge has to be created. When I was doing this I was SSH’d into the NIC I was configuring (em1), and creating the bridge brought the interface down. So, either make sure you have physical access to the machine, or SSH into another NIC.
$ sudo ovs-vsctl add-br br0 $ sudo ovs-vsctl add-port br0 em1
Run the show command again, and we should have a configuration.
$ sudo ovs-vsctl show 7d84d624-632b-4d2c-93ad-56ad3cc543cc Bridge "br0" Port "em1" Interface "em1" Port "br0" Interface "br0" type: internal ovs_version: "2.0.2"
Now, the interfaces need to be configured.
$ sudo vim /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto em1 iface em1 inet static # The OVS bridge interface auto br0 iface br0 inet static address 10.0.0.4 network 10.0.0.0 netmask 255.255.0.0 broadcast 10.0.255.255 gateway 10.0.0.2 dns-nameservers 184.108.40.206 220.127.116.11 dns-search test.local bridge_ports em1 bridge_fd 9 bridge_hello 2 bridge_maxage 12 bridge_stp off
This is just a copy of Scott’s configuration, with my network details in it.
At this point I rebooted the server and ran
ifconfig em1 up which brought my interface back up and I was able to SSH back into the machine.
Where the result of
ifconfig was previously…
$ ifconfig em1 Link encap:Ethernet HWaddr a4:ba:db:4d:0f:82 inet addr:10.0.0.4 Bcast:10.0.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:74620 errors:0 dropped:0 overruns:0 frame:0 TX packets:2094 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:7873976 (7.8 MB) TX bytes:216238 (216.2 KB)
$ ifconfig br0 Link encap:Ethernet HWaddr a4:ba:db:4d:0f:82 inet addr:10.0.0.4 Bcast:10.0.255.255 Mask:255.255.0.0 inet6 addr: fe80::a6ba:dbff:fe4d:f82/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:73075 errors:0 dropped:257 overruns:0 frame:0 TX packets:2101 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:6283264 (6.2 MB) TX bytes:199006 (199.0 KB) em1 Link encap:Ethernet HWaddr a4:ba:db:4d:0f:82 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:74620 errors:0 dropped:0 overruns:0 frame:0 TX packets:2094 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:7873976 (7.8 MB) TX bytes:216238 (216.2 KB)
So, I’m actually connecting to the bridge interface rather than the NIC.
Hopefully, this is just the beginning of an interesting adventure, in the meantime I’m going to read this again.