OpenVz is an open source operating system-level virtualization technology based on the Linux Kernel. OpenVz allows a Physical server to run multiple isolated operating system instance, Known as Virtual Private server (VPS) . The main Difference between Openvz and other virtualization software such as Vmware and KVM is that Under OpenVZ all the virtualized Operating system use the same kernel of the host operating system while compare in vmware and kvm each vps uses separated kernel which makes extra overhead. OpenVZ is the open-source branch of Virtuozzo, a commercial virtualization solution used by many providers that offer VPS.
Virtualization and Isolation Level Provided by the OpenVZ
Users and groups → Each VPS has its own root users, as well as other users and groups. Process tree → VPS only sees its own processes (starting from init). PIDs are virtualized, so that the init PID is 1. Network → Virtual network device, which allows a VPS to have its own IP addresses, as well as a set of netfilter (iptables) and routing rules.
Storage → Each VPS has its own Hard Disk which is dynamically resizable.Files → VPS has their own System libraries, virtualized /proc.
Devices → We can grant access to any VPS to use the real hardware like the network interfaces, storage Devices on the Host Operating system.
HN(Host Node) → Computer in which you run all the VPS The HOST NODE has access to all the Hardware resources available, HN can control the process running its self and inside a VPS . Another name for HOST NODE CT0 AND VE0
CT/VE/VPS (ConTainer / Virtual Environment / Virtual Private Server) → Another names for the VPS or the OS that we installed inside the HOST NODE. VPS is nothing but an isolated program execution environment which looks and feel like a separate physical server. Each VPS has file system, root user , normal users , firewall , system quota and much more . You can setup multiple VPSs within a single HOST NODE. Different VPSs can different Linux Distributions But all VPSs operate Under the same Kernel
CTID(Container ID) → Each VPS has a unique number called CTID (a ConTainer's IDentifer). CTID is just a number like 101 or 102. An administrator can use this number to identify the VPS. We set this number to a VPS at the time we create that VPS. After that admin can use this number to start, stop, restart, delete VPS and other administrative jobs related to your VPS.
VPS Templates → VPS templates are images of linux Distributions which are used to create a VPS. A template contain only minimal number of packages . Template will be in a compressed format ( Gzip , Bzip ). When we create our VPS using templates we have to Extract it to some folder.
VPS commands
"Vzctl is a management tool Provided by the Openvz to create , start , stop , and setting various type of resource parameters for a VPS like Memory,Disk quota, swap space . And so on."
1. Creating a VPS -
syntax :: vzctl create CTID --ostemplate TEMPLATE_NAME
[root@openvz] # vzctl create 101 --ostemplate centos-6-x86_64
2. Setting IP Address -
syntax :: vzctl set CTID --ipadd IP_ADDRESS --save
[root@openvz] # vzctl set 101 --ipadd 192.168.0.101 --save
" --save switch will save the configuration permanently "
3. Setting the Host Name -
syntax :: vzctl set CTID --hostname HOST_NAME --save
[root@openvz] # vzctl set 101 --hostname virtual101.virtual.com --save
4. Setting the Name server -
syntax :: vzctl set CTID --nameserver NAME_SERVER --save
[root@openvz] # vzctl set 101 --nameserver 192.168.0.254 --save
5. Setting the Hard Disk Size -
syntax :: vzctl set CTID --diskspace 5G:5G --save
6. Setting the root Passwd -
Syntax :: vzctl set 101 --userpasswd root:PASSWORD
[root@openvz] # vzctl set 101 --userpasswd root:linuxway
"vzctl command is use to create and mange VPS the Create option is for creating VPS and set options is for setting various parameters of the VPS like Hard disk space, Name Server IP , Root Password , IP Address ".
7. Listing all the Container/VPS Using vzlist-
[root@openvz ~]# vzlist -a
CTID NPROC STATUS IP_ADDR HOSTNAME
2034 31 running 172.16.9.208 ranjith.net
2035 - stopped 192.168.2.102 ranjith-test1.net
2037 29 running 172.16.9.209 ranjith-test2.net
2038 16 running 192.168.2.101 ranjith-test4.net
2039 16 running 192.168.2.100 ranjith-test3.net
[root@openvz ~]#
"vzlist -a shows that Container 2035 is stopped That is why the Number of Process is empty "
Command vzlist without any argument shows the running VPS only, otherwise vzlist -a shows all the VPS(both running and stopped)
[root@openvz ~]# vzlist
CTID NPROC STATUS IP_ADDR HOSTNAME
2034 31 running 172.16.9.208 ranjith.net
2037 29 running 172.16.9.209 ranjith-test2.net
2038 16 running 192.168.2.101 ranjith-test4.net
2039 16 running 192.168.2.100 ranjith-test3.net
[root@openvz ~]#
8. Starting VPS -
Syntax :: vzctl start CTID
[root@openvz ~]# vzctl start 2035
Starting container ...
Running: /usr/sbin/vzquota show 2035
Running: /usr/sbin/vzquota on 2035 -r 0 -b 5242980 -B 6291556 -i 200100 -I 220100 -e 0 -n 0 -s 0
Mounting root: /vz/root/2035 /vz/private/2035
Container is mounted
Set iptables mask 0x000017bf
Set features mask 0000000000000003/0000000000000003
Adding IP address(es): 192.168.2.102
Running: /usr/lib64/vzctl/scripts/vps-net_add
Running container script: /etc/vz/dists/scripts/redhat-add_ip.sh
Setting CPU units: 1000
Configuring meminfo: 262144
Set hostname: ranjith-test1.admod.net
Running container script: /etc/vz/dists/scripts/redhat-set_hostname.sh
Running: /usr/sbin/vzquota stat 2035 -f
Running: vzquota setlimit 2035 -b 5242880 -B 6291456 -i 200000 -I 220000 -e 0 -n 0
Container start in progress...
[root@openvz ~]# vzlist -a
CTID NPROC STATUS IP_ADDR HOSTNAME
2034 31 running 172.16.9.208 ezranjith.net
2035 29 running 192.168.2.102 ranjith-test1.net
2037 29 running 172.16.9.209 ranjith-test2.net
2038 16 running 192.168.2.101 ranjith-test4.net
2039 16 running 192.168.2.100 ranjith-test3.net
[root@openvz ~]#
"Now The VPS is up and Running and we can connect to the VPS from the Host-Node using SSH"
9. Connecting to the Container from outside-
~$ ssh root@172.16.9.209
The authenticity of host '172.16.9.209 (172.16.9.209)' can't be established.
RSA key fingerprint is b9:96:17:7e:63:5d:16:f3:64:e8:6b:a9:79:d3:54:dd.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '172.16.9.209' (RSA) to the list of known hosts.
root@172.16.9.209's password:
Last login: Wed Feb 27 17:09:14 2013 from 172.16.9.208
[root@ranjith-test2 ~]#
10. Checking the Disk Usage inside the VPS-
[root@openvz ~]# vzctl enter 2037
entered into CT 2037
Open /dev/pts/0
[root@ranjith-test2 /]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/simfs 4.7G 1.4G 2.4G 37% /
[root@ranjith-test2 /]#
10. Checking the memory Usage inside the VPS-
[root@ranjith-test2 /]# free -m
total used free shared buffers cached
Mem: 1024 165 858 0 0 0
-/+ buffers/cache: 165 858
Swap: 0 0 0
[root@ranjith-test2 /]#
11. Checking the memory usage of the Host Node while VPS is running-
[root@openvz ~]# free -m
total used free shared buffers cached
Mem: 2006 620 1386 0 22 314
-/+ buffers/cache: 283 1723
Swap: 1027 0 1027
[root@openvz ~]#
12. Stopping the VPS -
Syntax :: vzctl stop CTID
[root@openvz ~]# vzctl stop 2035
Stopping container ...
Container was stopped
Running: /usr/lib64/vzctl/scripts/vps-net_del
Running: /usr/sbin/vzquota stat 2035 -f
Running: /usr/sbin/vzquota off 2035
Container is unmounted
[root@openvz ~]# vzlist -a
CTID NPROC STATUS IP_ADDR HOSTNAME
2034 34 running 172.16.9.208 ranjith.net
2035 - stopped 192.168.2.102 ranjith-test1.net
2037 29 running 172.16.9.209 ranjith-test2.net
2038 16 running 192.168.2.101 ranjith-test4.net
2039 16 running 192.168.2.100 ranjith-test3.net
[root@openvz ~]#
13. Restarting the VPS -
Syntax :: vzctl restart CTID
[root@openvz ~]# vzctl restart 2035
Restarting container
Starting container ...
Running: /usr/sbin/vzquota show 2035
Running: /usr/sbin/vzquota on 2035 -r 0 -b 5242980 -B 6291556 -i 200100 -I 220100 -e 0 -n 0 -s 0
Mounting root: /vz/root/2035 /vz/private/2035
Container is mounted
Set iptables mask 0x000017bf
Set features mask 0000000000000003/0000000000000003
Adding IP address(es): 192.168.2.102
Running: /usr/lib64/vzctl/scripts/vps-net_add
Running container script: /etc/vz/dists/scripts/redhat-add_ip.sh
Setting CPU units: 1000
Configuring meminfo: 262144
Set hostname: ranjith-test1.admod.net
Running container script: /etc/vz/dists/scripts/redhat-set_hostname.sh
Running: /usr/sbin/vzquota stat 2035 -f
Running: vzquota setlimit 2035 -b 5242880 -B 6291456 -i 200000 -I 220000 -e 0 -n 0
Container start in progress...
[root@openvz ~]# vzlist -a
CTID NPROC STATUS IP_ADDR HOSTNAME
2034 34 running 172.16.9.208 ezranjith.net
2035 29 running 192.168.2.102 ranjith-test1.net
2037 29 running 172.16.9.209 ranjith-test2.net
2038 16 running 192.168.2.101 ranjith-test4.net
2039 16 running 192.168.2.100 ranjith-test3.net
[root@openvz ~]#
Each VPS have their own configuration file where it save's all its information like ipaddress, disk space, domain name etc.., vzctl uses the set option to set the values and saves these values permanently when --save option is used. At the time of the VPS creation vzctl will create a folder under the /vz/private/ this where openvz saves its file system and data permanently . When we start the VPS openvz will use this directory /vz/root/ . as a mount point to mount its file system which are extracted into the /vz/private/ . when we stop the VPS openvz will umount the VPS file system from /vz/root/ , and saves all the changes permanently to /vz/private/ .
Private Directory of VPS 2034: /vz/private/2034
root Directory of VPS 2034 : /vz/root/2034
Configuration file of VPS 2034 : /etc/vz/conf/2034.conf
OpenVz Configuration file : /etc/vz/vz.conf
14. Executing commands inside VPS from HostNode-
Vzctl provides a method for executing the command inside the VPS without entering into the VPS. These can be very useful when we can to run only a single command.
Eg. run df -h inside VPS 2034
[root@openvz ~]# vzctl exec 2034 df -h
Filesystem Size Used Avail Use% Mounted on
/dev/simfs 4.7G 1.3G 2.4G 36% /
[root@openvz ~]#
