Virtualization using openVZ and easyVZ
By: Showayb A A Zahda
It is one of the most interesting and exciting things to run many operating systems at the
same time on a single computer. You can probably test some software on different
environments without the need to buy several computers. Or you can have several servers
at the same machine running different services in which you distribute the job of the
services into different operating systems. And having a stronger security.
Of course that is possible and doable using virtualization. Virtualization is basically
running several operating systems at the same time on top of one operating system. They
all share the resources of the machine like CPU, RAM, Hard disk, etc. Each system will
run in its environment and will not affect other systems. Moreover, we can connect all of
them using the virtual network.
In this humble tutorial I will explain for you how to use virtualization to run several
operating systems on Linux box. I will use openVZ and on top of it I will use the GUI
easyVZ to make the virtualization look prettier and nicer.
To start, you need to have your kernel compiled with openVZ. Check that using
#uname -a
The output should look something like Linux ... 2.6.188.1.8.el5.028stab038.1 ..
The most important part is 028stab038, if you do not have this (the numbers might be
different on your machine) you need to update your kernel using yum. So, make sure you
are connected to the Internet. To update the kernel you need first to update your yum
repository.
#cd /etc/yum.repos.d
#wget http://download.openvz.org/openvz.repo
#cd
Till now you have just updated your repository so as to use it for yum.
#yum -y install ovzkernel
After this step is done, you several things will change beside the kernel update. One of
them is the boot loader. I am using Centos 5, so my boot loader is GRUB. What happens
is that the yum installer will add extra entry to /boot/grub/grub.con looks like
title Cenros (2.6.8-022stab029.1)
root (hd0,0)
kernel /vmlinuz-2.6.8-022stab029.1 ro
root=/dev/sda5
initrd /initrd-2.6.8-022stab029.1.img
Note the “stab” in the entry
I believe you know how to edit GRUB configuration file to make this entry the default
boot option.
After this step we have to make some changes on some configuration files to make our
virtualization runs with no problem.
First file to be edited is the system control file. /etc/sysctl.conf
// change these entries
# On Hardware Node we generally need
# packet forwarding enabled and proxy arp disabled
net.ipv4.ip_forward = 1
# Enables the magic-sysrq key
kernel.sysrq = 1
# Enables source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.proxy_arp = 0
// add these entries at the bottom
net.ipv4.conf.default.proxy_arp = 0
net.ipv4.conf.default.send_redirects = 1
net.ipv4.conf.all.send_redirects = 0
Do not forget to save the file.
Now the next file to be changed is /etc/sysconfig/selinux
SELINUX=disabled
Make sure that selinux is disabled.
Ok by now your virtualization is half way, you need to reboot your machine.
#reboot
After your reboot is completed. you need to ensure that you have booted to the correct
kernel
#uname -a
The output should look something like Linux ... 2.6.188.1.8.el5.028stab038.1 ..
Now is the time to install the tools of openVZ.
#yum -y install vzctl vzquota vzpkg
After the installation is completed we can start our service of virtualization.
#/etc/init.d/vz start
or
#service vz start
Until here we have our virtualization program setup and running. Let's see how this thing
work.
In openVZ as other virtualization tools, you must have images of your operating systems
that you want to run on the host machine. The host machine is the machine that you are
running every thing on. So, in openVZ the operating system is called template. What is
inside a template? You can have the whole operating system and tools in the template
and you can have the minimum number of tools as well. It is customizable. In this
tutorial we will use one template that has been done by the openVZ people and do our
experiments on it.
In order to get ready made templates you can search them using yum
#yum search vztmpl
This will give you some output like this
vztmpl-centos-4.i386 2.0-2
openvz-utils
Matched from:
vztmpl-centos-4
vztmpl-fedora-7.i386 1.1-1
openvz-utils
Matched from:
vztmpl-fedora-7
vztmpl-fedora-core-6.i386 1.2-1
openvz-utils
Matched from:
vztmpl-fedora-core-6
vztmpl-fedora-core-3.i386 2.0-2
openvz-utils
Matched from:
vztmpl-fedora-core-3
vztmpl-fedora-core-4.i386 2.0-2
openvz-utils
Matched from:
vztmpl-fedora-core-4
vztmpl-fedora-core-5.i386 2.0-2
openvz-utils
Matched from:
vztmpl-fedora-core-5
vztmpl-centos-4.i386 2.0-2
installed
Matched from:
vztmpl-centos-4
now you pick the operating system of your interest and download it using yum. In my
case I prefer to use centos 4.5. The name of the tempalte usually looks like vztmpl
nameOfDistroversion.machine
#yum -y vztmpl-centos-4.i386
if you want to download another one you just need to change the name of the operating
system after vztmpl like
#yum -y vztmpl-fedora-7.i386
From here we need to have some understanding of the files of openVZ. Once you have
your template downloaded and installed. It will basically be extracted in the directory
/vz/template/centos/4/i388 . This is basically a mapping of the name to be extracted in
directories. So, /vz/emplate/nameOfDistro/version/machine/
and inside are the files of the system.
Now what you did is that just you have installed a small file which creates for you the
beginning of the job. In order to be able to run the system you have to have a file that
ends with .tar.gz. something like centos-4-i386-default.tar.gz saved in
/vz/template/cache/
To have this file you can use yum or download it manually.
To have things done easier I will use yum but this time it will be used via another
command called #vzpkgcache
this command will read what are the directories inside /vz/template/ and start
downloading the files of the system and store them in one file (tarball file) in
/vz/template/cache each operating system respectively. In my case I will only use one so
at the end I will have one tar file stored in /vz/template/cache/centos-4-
i386-default.ta.gz
Once you have this file or others, you can start the virtualization. Before that, let's list
what openVZ templates we have. use
#vzpkgls
the output would look like
centos-4-i386-default
You would have more names listed basically that is based on how many templates you
started.
At this stage we can start the virtualization.
To start the virtualization we need to create virtual private server VPS (if you do not
know this google it).
then we can start the virtualization.
to create VPS
# vzctl create 101 --ostemplate centos-4-i386-default
what does this mean?
vzctl means virtualization control
create : self explanatory
101: the VPS id which should be always any integer number above 100.
ostemplate: is an argument that takes the name of the template after it
centos4i386default: is the name of the template.
The output of this command looks like this
Creating VE private area (centos-4-i386-default)
Performing postcreate actions
VE private area was created
this will create a folder inside /vz/private/101
this folder has the root file system of Linux (/).
Notice that we did not configure anything yet. you can configure the network manully
from within the system or you can use vzctl again, let's use it
#vzctl set 101 --ipadd 192.168.0.18 –save
you can use any IP address you like
output:
Saved parameters for VE 101
#vzctl set 101 --nameserver 192.168.0.17 --save
you can use your own DNS server
output:
Saved parameters for VE 101
now we can start our our template
#vzctl start 101
Starting VE ...
VE is mounted
Adding IP address(es): 192.168.0.18
Setting CPU units: 1000
File resolv.conf was modified
VE start in progress...
now we have created our Virtual Environment (VE) and we can use it.
the next step is to try out some commands
you can execute Linux commands without the need to access the VPS. you need to do
this
#vzctl exec 101 service sshd start
exec means execute.
101 is the VPS id of the you VE.
service sshd start is a Linux command to start the ssh server.
the other way is that you access the VE and run the commands there
to access the VE
#vzctl enter 101
now you are in the VE.
Enjoy Linuxing there.
Well, I did not finish yet. I said at the beginning that you can run many operating
systems at the same time. so how?
just download another template, let's say fedora
and follow the same steps to cache the template then create it with different VPS id let's
say 102.
okay since you would have several operating systems running at the same time. How can
you know how many? what are they? etc.
#vzlist : means list the running virtual environments
Form the output you can know basic information of the VE that are running at your host
machines.
Now let's have a look at some command
#vzctl restart 101
this just stops and starts the VE again
#vzctl stop 101
this stops the VE so it cannot be used but the VPS id is still reserved for this template. if
you do not want this template anymore you can destroy it. Note: stop the VE then destroy
#vzctl destroy 101
Destroying VE private area: /vz/private/101
VE private area was destroyed
Since the aim of virtualization is to make several servers available and running always
we need to ensure that if the host is rebooted the virtual server is running too. This can
be achieved by
#vzctl set 101 --onboot yes --save
You can do some yumimg for the VE, so if you want to install screen program for the
VE 101
#vzyum 101 install screen
The vzyum is a program that installs the package for the VPS specified by the id. You
can do all the functions that are available by yum, so
#vzyum 101 update
#vzyum 101 upgrade packeage-name
You can have rpm packages as well
#vzrpm 101 -ivh rpm-package.rpm
To check how much space, cpu, and what not resources have been used by specific VPS.
#vzcalc v 101
v: virtual id
I wish this much of information have helped you to run openVZ
To run easyVZ which is the GUI of openVZ
download the package form here
http://binarykarma.com/?q=node/1
References:
http://www.serverworld.info/en/note?os=ce5&p=vz&f=1
http://wiki.openvz.org/Main_Page
http://binarykarma.com/?q=node/1
