Monday, October 31, 2011

VIMAGE - Better virtualization in FreeBSD 8

Now that FreeBSD 8 is out, among many changes we can find enhancements in the field of virtualization as well. A newly developed virtualization container calledVIMAGE has been implemented to enable virtualization of the FreeBSD network stack.
As you may know previous releases of FreeBSD had support only for jails with IP addresses of the main network stack; meaning once you configured IP/IPv6 addresses on your host system, a subset of those addresses could be associated to each one of your jails. As simple as it sounds, it actually doesn’t let you perform several networking related tasks inside of a jail, and you couldn’t separate your jails from each other with a firewall as there were no real interfaces present in your system.
With VIMAGE you have a jail with full instance of the host’s networking stack, including loopback interface, routing tables, etc. Network interfaces created on the host system can be moved to any VIMAGE jail to enable its connection to the outside world with a new option of ifconfig called “vnet”.
vnet jail
Move the interface to the jail , specified by name or JID. If the jail has a virtual network stack, the interface will disap- pear from the current environment and become visible to the jail.

Note: Option “-vnet” does the opposite.
As you might not have as many network interfaces as jails, you might need some workarounds to tunnel network traffic between two interfaces of your system.
Forget TUN/TAP and VPNs. FreeBSD 8 has a special network device called epair , which lets you create a pair of interconnected ethernet interfaces. If you move one of them to a VIMAGE jail you are basicly done. Feel free to bridge them or useVLANs, they will still work. I don’t know about the overhead of epair, but if all you care about is security, this might be the best choice for you on FreeBSD.
To enable VIMAGE you have to add “option VIMAGE” to your kernel configuration file and recompile/reinstall it.


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