OpenVZ is a virtualization technology similar to Solaris containers / BSD Jails etc. These kind of virtualization saves a lot of memory and run at almost full speed (very minimal overhead) whereas other virtualization techniques take a beat in the range of 5-25%. OpenVZ falls under the category called Operating system level virtualization

Installation:

I tried OpenVZ in Fedora 8 and OpenVZ binary kernel provided at openvz.org. Installing OpenVZ requires a modified Linux kernel. You can either install the binary kernel provided by openvz.org or we can download kernel source from kernel.org and compile the kernel after patching it using the patches provided.

Steps taken to install OpenVZ

everything following needs to be run as root

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cd /etc/yum.repos.d
wget http://download.openvz.org/openvz.repo
rpm --import  http://download.openvz.org/RPM-GPG-Key-OpenVZ

I used yum for installing the openvz

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yum install ovzkernel

we will have to edit /etc/systcl.conf and make sure these lines are present

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net.ipv4.ip_forward = 1
net.ipv4.conf.default.proxy_arp = 0
net.ipv4.conf.all.rp_filter = 1
kernel.sysrq = 1
net.ipv4.conf.default.send_redirects = 1
net.ipv4.conf.all.send_redirects = 0

next, we should disable selinux

edit /etc/sysconfig/selinux and set

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SELINUX=disabled

if you selected kernel version 2.6.8 or earlier then follow this step

edit /etc/modprobe.conf and add

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options ip_conntrack ip_conntrack_enable_ve0=1

reboot the system into newly installed OpenVZ kernel

After the system boots into OpenVZ kernel and follow these steps

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yum install vzctl vzquota

Installation is almost complete. We just need to start OpenVZ service it takes care of loading requires kernel modules etc.

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/sbin/service vz start

Now the OpenVZ has been successfully installed in my system.

Creation of Virtual Machine / Container:

I wanted to test “Suse 10″ and found that it is available as prebuilt OpenVZ distro (they call is template cache) at http://openvz.org/download/template/cache . Other prebuilt distributions includes asianux, centos, debian, fedora, gentoo, mandriva, ubuntu.

I had to just download the tarball in my case it is opensuse-10-i386-default.tar.gz and store it at /vz/template/cache. no need to untar it.

Creation of Virtual Machine or a Container

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vzctl create 101 --ostemplate opensuse-10-i386-default
vzctl set 101 --ipadd 10.1.2.3 --save
vzctl set 101 --nameserver 10.0.2.1 --save
vzctl start 101

Here 101 is the id we use to refer opensuse container. it can be anything above 100. create command creates a container with id 101 and we will be referring opensuse container using this container. –ipadd add a ipaddress to the container. default networking is done using venet driver and its simple, fast and secure but cannot acquire ip using dhcp etc. there is also veth driver which is a virtual ethernet device and can acqurire ip using dhcp but requries more configuration.

with –nameserver option with set the nameserver to be used by the container.

Running a program inside Container:

to run any command inside a container from the host system

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vzctl exec 101 ps -efww

this will run ps -efww and return the result.

if you want to login into the container

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vzctl enter 101

This tutorial is over. we will look into other advanced concepts like setting up networking using ethernet and others in upcoming tutorials.