OpenVZ On CentOS 5.4 installation and configuration

This article will describe how to create OpenVZ container in CentOS 5.4. With OpenVZ you can create multiple Virtual Private Servers (VPS) on same hardware machine and running them simultaneously and efficiently.

OpenVZ is the open-source branch of Virtuozzo, a commercial virtualization solution widely used by hosting providers. The OpenVZ kernel patch is licensed under GPL license, and the user-level tools are under the QPL license.

As there are many ways of achieving this goal, I’d keep this howto as smart as possible. In the following days, I’d create similar posts on Xen / Vserver, please keep a close eye on my planet.

1, Install OpenVZ

In order to install OpenVZ, we need to add the OpenVZ repository to yum, this would also help us keep the kernel up-to-date:

cd /etc/yum.repos.d
rpm --import

The repository contains a few different OpenVZ kernels (you can find more details here:, or with this command “yum search ovzkernel“.

Pick one of them and install it as follows:

yum install ovzkernel

This should automatically update the GRUB bootloader as well. An example is listed below”

cat /boot/grub/menu.lst
# grub.conf generated by anaconda
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
#          initrd /initrd-version.img
title CentOS (2.6.18-128.2.1.el5.028stab064.7)
	root (hd0,0)
	kernel /vmlinuz-2.6.18-128.2.1.el5.028stab064.7 ro root=LABEL=/
	initrd /initrd-2.6.18-128.2.1.el5.028stab064.7.img

2, Pre-adjustings before the installation

Now we install some OpenVZ user tools:

yum install vzctl vzquota

Open /etc/sysctl.conf and make sure that you have the following settings in it:

cat /etc/sysctl.conf

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

The following step is important if the IP addresses of your virtual machines are from a different subnet than the host system’s IP address. If you don’t do this, networking will not work in the virtual machines!

Open /etc/vz/vz.conf and set NEIGHBOUR_DEVS to all, the modified entry is like this “NEIGHBOUR_DEVS=all“. SELinux needs to be disabled, you can do it by making changes on its config file /etc/sysconfig/selinux. Finally, reboot the system, and then your new OpenVZ kernel should show up:

[root@server1 ~]# uname -r

3, Create a Virutal Server

Before we can create virtual machines with OpenVZ, we need to have a template for the distribution that we want to use in the virtual machines in the /vz/template/cache by default. New virtual machines will be created from these templates. A list of precreated templates is available here.

I want to use CentOS 5 in my virtual machines, so I download a CentOS 5 template:

cd /vz/template/cache

To set up a VPS from the default CentOS 5 template, run:

vzctl create 211 --ostemplate centos-5-i386-default --config vps.basic

The 211 must be uniqe and each virtual machine must have its own ID. You can use the last part of the VPS’s IP address for it. For example, if the virtual machine’s IP address is, you use 211 as the ID.


4, Common controls on OpenVZ

If you want to have the vm started at boot, run:

vzctl set 211 --onboot yes --save

To set a hostname and IP address for the vm, run:

vzctl set 211 --hostname --save
vzctl set 211 --ipadd --save

Next we set the number of sockets to 120 and assign a few nameservers to the vm:

vzctl set 211 --numothersock 120 --save
vzctl set 211 --nameserver --nameserver --nameserver --save

Instead of using the vzctl set commands, you can directly edit vm’s configuration file which is stored in the directory /etc/vz/conf. If the ID of the vm is 211, then the configuration file is /etc/vz/conf/211.conf.

In order to start the vm, run “vzctl start 211”, to set a root password for the vm, run “vzctl exec 211 passwd”. Now You can either connect to the vm via SSH (e.g. with PuTTY), or login through console directly as follows:

vzctl enter 211

To leave the vm’s console, type “exit”, to stop a vm, run “vzctl stop 211“, to restart a vm, run “vzctl restart 211“.

To delete a vm from the hard drive (it must be stopped before you can do this), run “vzctl destroy 211“.

5, Check VM Status

To get a list of your vms and their statuses, run “vzlist -a” like this:

[root@server1 cache]# vzlist -a
       211         18 running

To find out about the resources allocated to a vm, run like follows:

[root@server1 cache]# vzctl exec 211 cat /proc/user_beancounters
Version: 2.5
       uid  resource           held    maxheld    barrier      limit    failcnt
      211:  kmemsize        1508202    1661695   11055923   11377049          0
            lockedpages           0          0        256        256          0
            privvmpages        5430       7102      65536      69632          0
            shmpages            381        381      21504      21504          0
            dummy                 0          0          0          0          0
            numproc              19         21        240        240          0
            physpages          2489       2775          0 2147483647          0
            vmguarpages           0          0      33792 2147483647          0
            oomguarpages       2489       2775      26112 2147483647          0
            numtcpsock            5          5        360        360          0
            numflock              3          4        188        206          0
            numpty                0          1         16         16          0
            numsiginfo            0          2        256        256          0
            tcpsndbuf         44720          0    1720320    2703360          0
            tcprcvbuf         81920          0    1720320    2703360          0
            othersockbuf      13144      14356    1126080    2097152          0
            dgramrcvbuf           0       8380     262144     262144          0
            numothersock         11         13        120        120          0
            dcachesize            0          0    3409920    3624960          0
            numfile             503        531       9312       9312          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            dummy                 0          0          0          0          0
            numiptent            10         10        128        128          0

The failcnt column is very important, it should be only zeros; if not, means that the vm needs more resources than currently allocated. Open the vm’s configuration file in /etc/vz/conf and raise the appropriate resource, then restart it.

To find out more about the vzctl command, run “man vzctl”. If you faced any issues during the installation, please create a thread and show your errors  in the sub forum virtualization at admon community.

4 thoughts on “OpenVZ On CentOS 5.4 installation and configuration

  1. Nice post,thanks for sharing with us. Your site is much help for me, please keep it going!

  2. Hi! I could have sworn I’ve been to this web site before but after browsing through a few of the articles I realized it’s new to me.
    Anyways, I’m definitely happy I found it and I’ll be bookmarking it and checking back frequently!

Leave a comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.