Getting started with OpenVZ live CD

2007-06-10T16:51:56Z

Ongardie:

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 identified by its number -- a '''VEID'''.

== VE creation ==
So, how to create a VE with VEID of 101 based on Debian template? Very easy. Just type the following commands in your
terminal (you must be root):
<pre>
root@Knoppix:~# vzctl create 101 --ostemplate debian-3.1-i386-minimal
Creating VE private area (debian-3.1-i386-minimal)
Performing postcreate actions
VE private area was created
</pre>

'''vzctl''' is the tool that manages VEs. Look in <tt>/var/lib/vz/template/cache/</tt> directory for other OS templates available on LiveCD:
<pre>
root@Knoppix:~# ls -1 /var/lib/vz/template/cache/
centos-4-i386-minimal.tar.gz
debian-3.1-i386-minimal.tar.gz
fedora-core-5-i386-minimal.tar.gz
</pre>

== List of VEs ==
You can get the list of all created VEs on '''HN''' (Hardware Node) using '''vzlist''' command:
<pre>
root@Knoppix:~# vzlist -a
VEID NPROC STATUS IP_ADDR HOSTNAME
101 - stopped - -
</pre>

As you see, VE 101 is in stopped state now.

== Starting VE ==
Let's start it:
<pre>
root@Knoppix:~# vzctl start 101
Starting VE ...
VE is mounted
Setting CPU units: 1000
VE start in progress...
root@Knoppix:~# vzlist -a
VEID NPROC STATUS IP_ADDR HOSTNAME
101 5 running -
</pre>

o Note: In the LiveCD environment, you may have to increase SHMPAGES for the VE or you will run out of "disk space" when trying to install software. You can do this "on the fly" by issuing:

<pre>
' vzctl set 101 --shmpages $((8192*8)):$((8192*8)) --save '
</pre>

o This will give VE 101 64MB of shmpages; you may wish to give it more if you're planning on doing more than just basic openvz testing.

o You can verify the change from the host by issuing:

<pre>
' vzctl exec 101 cat /proc/user_beancounters '
</pre>

== Executing commands in VE ==
From the "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>
root@Knoppix:~# vzctl exec 101 ps
PID TTY TIME CMD
1 ? 00:00:00 init
7672 ? 00:00:00 rc
7674 ? 00:00:00 S10sysklogd
7677 ? 00:00:00 syslogd
7678 ? 00:00:00 syslogd
7683 ? 00:00:00 ps
</pre>

== Entering VE ==
Any self-respected OS provides a shell for the user. This is how you can get the VE's shell:
<pre>
root@Knoppix:~# vzctl enter 101
entered into VE 101
Knoppix:/#
</pre>

In this shell you can do almost all you can do on the real HN. For example create a new user:
<pre>
Knoppix:/# useradd new-user
Knoppix:/# passwd new-user
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Knoppix:/# mkdir /home/new-user
Knoppix:/# chown new-user /home/new-user/
Knoppix:/# su new-user
Knoppix:/$ cd ~
Knoppix:~$ pwd
/home/new-user
exit
Knoppix:/#
</pre>

In order to exit from VEs shell, just type exit:
<pre>
Knoppix:/# exit
logout
exited from VE 101
root@Knoppix:~#
</pre>

== Setting up VE networking ==
Let's set up networking in VE.

<pre>
root@Knoppix:~# echo 1 > /proc/sys/net/ipv4/ip_forward
root@Knoppix:~# ifconfig venet0 up
root@Knoppix:~# vzctl set 101 --ipadd 10.1.1.1 --save
Adding IP address(es): 10.1.1.1
Saved parameters for VE 1
root@Knoppix:~# vzlist -a
VEID NPROC STATUS IP_ADDR HOSTNAME
101 4 running 10.1.1.1 -
</pre>

Now your [[Hardware Node]] can ping VE and VE can ping HN:
<pre>
root@Knoppix:~# ping 10.1.1.1
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

--- 10.1.1.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 3.804/3.804/3.804/0.000 ms
root@Knoppix:~#
root@Knoppix:~# vzctl exec 101 ping 192.168.0.244
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

root@Knoppix:~#
</pre>

However, it is not possible to ping other computers in the network: for it we need to
set up NAT (Network Address Translation) and set the nameserver.

Assume that you've set up network on HN (for example via DHCP) and the IP address
of your node is 192.168.0.244 and nameserver IP address is 192.168.1.1.
<pre>
root@Knoppix:~# iptables -t nat -A POSTROUTING -s 10.1.1.1 -o eth0 -j SNAT --to 192.168.0.244
root@Knoppix:~# vzctl set 101 --nameserver 192.168.1.1 --save
File resolv.conf was modified
Saved parameters for VE 101
root@Knoppix:~# vzctl exec 101 ping google.com
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
</pre>

== 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 apt-get tool can be used.

Now, for example, we can install gcc inside VE 101 for developing purposes:
<pre>
root@Knoppix:~# vzctl enter 101
entered into VE 101
Knoppix:/#
Knoppix:/# apt-get install gcc
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
binutils cpp cpp-3.3 gcc-3.3
Suggested packages:
binutils-doc cpp-doc make manpages-dev autoconf automake libtool flex bison gdb gcc-doc gcc-3.3-doc
Recommended packages:
libc-dev libc6-dev
The following NEW packages will be installed:
binutils cpp cpp-3.3 gcc gcc-3.3
0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
Need to get 5220kB of archives.
After unpacking 13.6MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://ftp.freenet.de stable/main binutils 2.15-6 [2221kB]
Get:2 http://ftp.freenet.de stable/main cpp-3.3 1:3.3.5-13 [1393kB]
Get:3 http://ftp.freenet.de stable/main cpp 4:3.3.5-3 [29.6kB]
Get:4 http://ftp.freenet.de stable/main gcc-3.3 1:3.3.5-13 [1570kB]
Get:5 http://ftp.freenet.de stable/main gcc 4:3.3.5-3 [4906B]
Fetched 5220kB in 10s (507kB/s)
Selecting previously deselected package binutils.
(Reading database ... 7436 files and directories currently installed.)
Unpacking binutils (from .../binutils_2.15-6_i386.deb) ...
Selecting previously deselected package cpp-3.3.
Unpacking cpp-3.3 (from .../cpp-3.3_1%3a3.3.5-13_i386.deb) ...
Selecting previously deselected package cpp.
Unpacking cpp (from .../cpp_4%3a3.3.5-3_i386.deb) ...
Selecting previously deselected package gcc-3.3.
Unpacking gcc-3.3 (from .../gcc-3.3_1%3a3.3.5-13_i386.deb) ...
Selecting previously deselected package gcc.
Unpacking gcc (from .../gcc_4%3a3.3.5-3_i386.deb) ...
Setting up binutils (2.15-6) ...

Setting up cpp-3.3 (3.3.5-13) ...
Setting up cpp (3.3.5-3) ...
Setting up gcc-3.3 (3.3.5-13) ...
Setting up gcc (3.3.5-3) ...

Knoppix:/# exit
logout
exited from VE 101
root@Knoppix:~#
</pre>

== 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. Current usage values and limits of memory-related resources can be viewed through
<code>/proc/bc/VEID/resources</code> file:
<pre>
root@Knoppix:~# cat /proc/bc/101/resources
kmemsize 628209 976969 2752512 2936012 0
lockedpages 0 0 32 32 0
privvmpages 5238 6885 49152 53575 0
shmpages 5012 5014 8192 8192 0
numproc 3 11 65 65 0
physpages 5084 6020 0 2147483647 0
vmguarpages 0 0 6144 2147483647 0
oomguarpages 5084 6020 6144 2147483647 0
numtcpsock 0 2 80 80 0
numflock 1 5 100 110 0
numpty 0 1 16 16 0
numsiginfo 0 6 256 256 0
tcpsndbuf 0 4440 319488 524288 0
tcprcvbuf 0 42180 319488 524288 0
othersockbuf 2220 6660 132096 336896 0
dgramrcvbuf 0 2220 132096 132096 0
numothersock 1 6 80 80 0
dcachesize 0 0 1048576 1097728 0
numfile 106 339 2048 2048 0
numiptent 10 10 128 128 0
root@Knoppix:~#
</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.

Note that if you have nonzero values in the last column, it means that this VE
experienced a resource shortage. This is very common reason why some application fail to
work in a VE. In this case you should increase limits/barriers accordingly; see
[[resource shortage]] for more info.

== Stopping/removing VE ==
Well, let's stop VE and destroy it:
<pre>
root@Knoppix:~# vzctl stop 101
Stopping VE ...
VE was stopped
VE is unmounted
root@Knoppix:~# vzctl destroy 101
Destroying VE private area: /var/lib/vz/private/101
VE private area was destroyed
root@Knoppix:~#
</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/ .

OpenVZ Virtuozzo Containers Wiki - User contributions [en]

Getting started with OpenVZ live CD