Virtualization With KVM On A CentOS 6.4 Server
Version 1.0
Author: Falko Timme <ft [at] falkotimme [dot] com>
Last edited 03/22/2013
This guide explains how you can install and use KVM for creating and running virtual machines on a CentOS 6.4 server. I will show how to create image-based virtual machines and also virtual machines that use a logical volume (LVM). KVM is short for Kernel-based Virtual Machine and makes use of hardware virtualization, i.e., you need a CPU that supports hardware virtualization, e.g. Intel VT or AMD-V.
I do not issue any guarantee that this will work for you!
1 Preliminary Note
I’m using a CentOS 6.4 server with the hostname server1.example.com and the IP address 192.168.0.100 here as my KVM host.
I had SELinux disabled on my CentOS 6.4 system. I didn’t test with SELinux on; it might work, but if not, you better switch off SELinux as well:
vi /etc/selinux/config
Set SELINUX=disabled…
# This file controls the state of SELinux on the system. |
… and reboot:
reboot
We also need a desktop system where we install virt-manager so that we can connect to the graphical console of the virtual machines that we install. I’m using a Fedora 17 desktop here.
2 Installing KVM
CentOS 6.4 KVM Host:
First check if your CPU supports hardware virtualization – if this is the case, the command
egrep ‘(vmx|svm)’ –color=always /proc/cpuinfo
should display something, e.g. like this:
[root@server1 ~]# egrep ’(vmx|svm)’ –color=always /proc/cpuinfo
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall
nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy misalignsse
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall
nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy misalignsse
[root@server1 ~]#
If nothing is displayed, then your processor doesn’t support hardware virtualization, and you must stop here.
Now we import the GPG keys for software packages:
rpm –import /etc/pki/rpm-gpg/RPM-GPG-KEY*
To install KVM and virtinst (a tool to create virtual machines), we run
yum install kvm libvirt python-virtinst qemu-kvm
Then start the libvirt daemon:
/etc/init.d/libvirtd start
To check if KVM has successfully been installed, run
virsh -c qemu:///system list
It should display something like this:
[root@server1 ~]# virsh -c qemu:///system list
Id Name State
———————————-
[root@server1 ~]#
If it displays an error instead, then something went wrong.
Next we need to set up a network bridge on our server so that our virtual machines can be accessed from other hosts as if they were physical systems in the network.
To do this, we install the package bridge-utils…
yum install bridge-utils
… and configure a bridge. Create the file /etc/sysconfig/network-scripts/ifcfg-br0 (please use the IPADDR, PREFIX, GATEWAY, DNS1 and DNS2 values from the /etc/sysconfig/network-scripts/ifcfg-eth0 file); make sure you use TYPE=Bridge, not TYPE=Ethernet:
vi /etc/sysconfig/network-scripts/ifcfg-br0
DEVICE="br0" |
Modify /etc/sysconfig/network-scripts/ifcfg-eth0 as follows (comment out BOOTPROTO, IPADDR, PREFIX, GATEWAY, DNS1, and DNS2 and add BRIDGE=br0):
vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0" |
Restart the network…
/etc/init.d/network restart
… and run
ifconfig
It should now show the network bridge (br0):
[root@server1 ~]# ifconfig
br0 Link encap:Ethernet HWaddr 00:1E:90:F3:F0:02
inet addr:192.168.0.100 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::21e:90ff:fef3:f002/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:460 (460.0 b) TX bytes:2298 (2.2 KiB)
eth0 Link encap:Ethernet HWaddr 00:1E:90:F3:F0:02
inet6 addr: fe80::21e:90ff:fef3:f002/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:18455 errors:0 dropped:0 overruns:0 frame:0
TX packets:11861 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:26163057 (24.9 MiB) TX bytes:1100370 (1.0 MiB)
Interrupt:25 Base address:0xe000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:5 errors:0 dropped:0 overruns:0 frame:0
TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2456 (2.3 KiB) TX bytes:2456 (2.3 KiB)
virbr0 Link encap:Ethernet HWaddr 52:54:00:AC:AC:8F
inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
[root@server1 ~]#
3 Installing virt-viewer Or virt-manager On Your Fedora 17 Desktop
Fedora 17 Desktop:
We need a means of connecting to the graphical console of our guests – we can use virt-manager for this. I’m assuming that you’re using a Fedora 17 desktop.
Become root…
su
… and run…
yum install virt-manager libvirt qemu-system-x86 openssh-askpass
… to install virt-manager.
(If you’re using an Ubuntu 12.04 desktop, you can install virt-manager as follows:
sudo apt-get install virt-manager
)
4 Creating A Debian Squeeze Guest (Image-Based) From The Command Line
CentOs 6.4 KVM Host:
Now let’s go back to our CentOS 6.4 KVM host.
Take a look at
man virt-install
to learn how to use virt-install.
We will create our image-based virtual machines in the directory /var/lib/libvirt/images/ which was created automatically when we installed KVM in chapter two.
To create a Debian Squeeze guest (in bridging mode) with the name vm10, 512MB of RAM, two virtual CPUs, and the disk image /var/lib/libvirt/images/vm10.img (with a size of 12GB), insert the Debian Squeeze Netinstall CD into the CD drive and run
virt-install –connect qemu:///system -n vm10 -r 512 –vcpus=2 –disk path=/var/lib/libvirt/images/vm10.img,size=12 -c /dev/cdrom –vnc –noautoconsole –os-type linux –os-variant debiansqueeze –accelerate –network=bridge:br0 –hvm
Of course, you can also create an ISO image of the Debian Squeeze Netinstall CD (please create it in the /var/lib/libvirt/images/ directory because later on I will show how to create virtual machines through virt-manager from your Fedora desktop, and virt-manager will look for ISO images in the /var/lib/libvirt/images/ directory)…
dd if=/dev/cdrom of=/var/lib/libvirt/images/debian-6.0.5-amd64-netinst.iso
… and use the ISO image in the virt-install command:
virt-install –connect qemu:///system -n vm10 -r 512 –vcpus=2 –disk path=/var/lib/libvirt/images/vm10.img,size=12 -c /var/lib/libvirt/images/debian-6.0.5-amd64-netinst.iso –vnc –noautoconsole –os-type linux –os-variant debiansqueeze –accelerate –network=bridge:br0 –hvm
The output is as follows:
[root@server1 ~]# virt-install –connect qemu:///system -n vm10 -r 512 –vcpus=2 –disk path=/var/lib/libvirt/images/vm10.img,size=12 -c /var/lib/libvirt/images/debian-6.0.5-amd64-netinst.iso –vnc –noautoconsole –os-type linux –os-variant debiansqueeze –accelerate –network=bridge:br0 –hvm
Starting install…
Allocating ’vm10.img’ | 12 GB 00:00
Creating domain… | 0 B 00:00
Domain installation still in progress. You can reconnect to
the console to complete the installation process.
[root@server1 ~]#
Virtualization With KVM On A CentOS 6.4 Server
Virtualization With KVM On A CentOS 6.4 Server