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This article is written for OpenVZ LiveCD and assumes that the reader only starts using OpenVZ.([[Download live CD]])
== Introduction ==
So, as you probably know, OpenVZ allows the user to create [[VE]]s, or Virtual Environments, which seem very much
like real computers. Real computer can run various distributions: Debian, Gentoo, Red Hat and Novell products, etc.
In the same way, a VE can be based on various [[OS template|OS (Operating System) templates]]. On the LiveCD only few minimal OS templates are installed because of disk space limit. Each VE is indentified identified by its number -- a '''VEID'''.
== VE creation ==
terminal (you must be root):
<pre>
Creating VE private area (debian-3.1-i386-minimal)
Performing postcreate actions
</pre>
'''vzctl''' is the tool that manages VEs. Look in <tt>/vz/template/cache/</tt> (CentOS LiveCD)or in <tt>/var/lib/vz/template/cache/</tt> directory (KNOPPIX LiveCD) directories for other OS templates available on LiveCD:
<pre>
centos-4-i386-minimal.tar.gz
debian-3.1-i386-minimal.tar.gz
You can get the list of all created VEs on '''HN''' (Hardware Node) using '''vzlist''' command:
<pre>
VEID NPROC STATUS IP_ADDR HOSTNAME
101 - stopped - -
Let's start it:
<pre>
Starting VE ...
VE is mounted
Setting CPU units: 1000
VE start in progress...
VEID NPROC STATUS IP_ADDR HOSTNAME
101 5 running -
== Executing commands in VE ==
From the previous "vzlist" command you see that 5 processes are running inside VE 101. (The "NPROC" field indicates the number of Processes, or PIDs, that are active in the VE -- not the number of Processors, or CPUs.) Being on usual [[hardware node]] you can use <code>ps</code> command to identify those, and the same command can be used here. The only difference is that this command should be called inside VE.
In order to perform any command inside VE `vzctl exec` is used:
<pre>
PID TTY TIME CMD
1 ? 00:00:00 init
Any self-respected OS provides a shell for the user. This is how you can get the VE's shell:
<pre>
entered into VE 101
</pre>
In this shell you can do almost all you can do on the real HN. For example create a new user:
<pre>
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
/home/new-user
exit
</pre>
In order to exit from VEs shell, just type exit:
<pre>
logout
exited from VE 101
</pre>
<pre>
Adding IP address(es): 10.1.1.1
Saved parameters for VE 1
VEID NPROC STATUS IP_ADDR HOSTNAME
101 4 running 10.1.1.1 -
Now your [[Hardware Node]] can ping VE and VE can ping HN:
<pre>
PING 10.1.1.1 (10.1.1.1) 56(84) bytes of data.
64 bytes from 10.1.1.1: icmp_seq=1 ttl=64 time=3.80 ms
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 3.804/3.804/3.804/0.000 ms
PING 192.168.0.244 (192.168.0.244) 56(84) bytes of data.
64 bytes from 192.168.0.244: icmp_seq=1 ttl=64 time=0.508 ms
</pre>
of your node is 192.168.0.244 and nameserver IP address is 192.168.1.1.
<pre>
File resolv.conf was modified
Saved parameters for VE 101
PING google.com (64.233.167.99) 56(84) bytes of data.
64 bytes from py-in-f99.google.com (64.233.167.99): icmp_seq=1 ttl=241 time=23.0 ms
== Installing software inside VE ==
I guess you've noted that there is not so many packages in VE. It is because minimal template was used.
But of course, you can install any software in VE by yourself. For example, in Debian usual <tt>apt-get </tt> tool can be used.
Now, for example, we can install gcc inside VE 101 for developing purposes:
<pre>
entered into VE 101
Reading Package Lists... Done
Building Dependency Tree... Done
Setting up gcc (3.3.5-3) ...
logout
exited from VE 101
</pre>
{{ Note|In the LiveCD environment, you may have to increase '''shmpages''' resource limit/barrier for the VE (read the next section) or you will run out of "disk space" when trying to install software }}
== Resource limiting ==
The very important feature of VE is that you can limit it by resources: CPU, memory, disk space.
It is also performed via vzctl. For example to set '''shmpages''' (shared memory pages) barrier:limit youshould give this command:<pre>vzctl set 101 --shmpages 16384:16384 --save</pre>This will give VE 101 64MB of '''shmpages''' (one page equals 4Kb on i386: 4Kb * 16384 = 64Mb) Current usage values and limits of memory-related resources can be viewed through
<code>/proc/bc/VEID/resources</code> file:
<pre>
kmemsize 628209 976969 2752512 2936012 0
lockedpages 0 0 32 32 0
numfile 106 339 2048 2048 0
numiptent 10 10 128 128 0
</pre>
First column is resource name, second is current usage, third is peak usage, forth and fifth are barrier and limit, and last column is fail counter.
Well, let's stop VE and destroy it:
<pre>
Stopping VE ...
VE was stopped
VE is unmounted
Destroying VE private area: /var/lib/vz/private/101
VE private area was destroyed
</pre>
== Links ==
That's all you need to start playing with OpenVZ. Additional information can be found in man page on vzctl and at http://wiki.openvz.org/ . If you experience some difficulties, contact us via http://forum.openvz.org/ . Templates and other tools are available from http://download.openvz.org/.
