A quick introduction to OpenVZ, a virtualization platform for Linux that works like FreeBSD jails - it segments a system into different partitions, all running LInux. Each virtual system, container, can run different Linux distributions.

1. Introduction to OpenVZ
oej@edvina.net
Olle E.
oej@edvina.net Johansson * oej@edvina.net * Twitter oej
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2. OpenVZ
• Virtualization software by Parallells, inc.
Base for their commercial Virtuozzo
platform
• Integrated with the virtualization
support in the kernel - lvc
• Segmentation, not full virtualization
• Regardless, has cool features
Introduction to
OpenVZ

3. Cool features
• Migration of running system
• Backup with just a few secs stop time
• Very simple - shared filesystem in the
host system
Introduction to
OpenVZ

4. Basics
Containers share the
same kernel. Only Linux is
supported - but you can run
Kernel a different distribution in
Container 1 a container.
OpenVZ
The host system
Containers get allocated a few
runs a full Linux with a
Container 2 resources - network, CPU,
standard kernel with
memory, disk.
openvz extensions.
Introduction to
OpenVZ

5. The container is a full
Linux system
• The container is a full Linux system
• It has network interfaces (if configured)
• It has a separate user account database (/etc/passwd)
• It needs patching and updates like any other system
Introduction to
OpenVZ

6. The Kernel
• The kernel is managed as an package for
the distro you are using.
• For Centos, you add a new yum
repository and install the kernel
• Reboot and you have OpenVZ support
• Now install the tools - vzsplit, vzctl and
vzlist
Introduction to
OpenVZ

7. vzctl
• Used to manage containers
• Create new container
• Start container
• Stop container
• Change attributes (name, IP address, various limits,
properties)
Introduction to
OpenVZ

8. vzlist
• Simply list containers running in a system
• Lists all container IDs
Introduction to
OpenVZ

9. vzsplit
• Used to get settings for vzctl (or the .conf
files)
• Takes all resources in a server and divides
them between a specific number of
containers
Introduction to
OpenVZ

10. Beancounters
• Counters that document use
• Also document when a resource limit is
exceeded
• cat /proc/user_beancounters
• Used to design system and manage issues
• Watch the failcnt column!
Introduction to
OpenVZ

11. Networking
• Ethernet interface via nat or bridge
• The bridge interface enables DHCP and
other broadcast /multicast technologies
• IPv4 and IPv6 support
• Firewall with IPtables in container or
outside in host system (on the bridge)
• Network traffic can be managed Introduction to
OpenVZ

12. Script hooks
• There are hooks for scripts you can run
when starting and stopping containers
• These can be used to mount disk drives
into container
Introduction to
OpenVZ

13. Configuration
• Configuration file in /etc/vz/vz.conf
• Configuration for containers in /etc/vz/
conf
Introduction to
OpenVZ

14. Advanced features
• Live migration of containers between
systems
• Backup of running system
• Remote management with libvirt
Introduction to
OpenVZ

15. References
• www.openvz.org
• Documentation
• Wiki full with information, howto’s and documentation
• Downloadable templates for containers - Centos,
Debian, Ubuntu and other distributions
Introduction to
OpenVZ