Fleet and flexible cgroups and Linux Containers

Virtual Host

Article from Issue 130/2011

The big virtualization tools like KVM and Xen can’t compete on a small scale with resource-spare cgroups and Linux Containers.

Normally when I talk about virtualization in Linux, I go straight to system virtualization using tools like KVM or Xen, to name two. But some interesting options aren’t quite as well known. One such example is cgroups [1] and Linux Containers [2] (LXC), which sits on top of cgroups. In a nutshell, LXC uses cgroups to create a restricted view of the host operating system. Within the LXC guest environment, you can only see what the admin allows you to see of the host system; you can have a separate process space, for example and also create a separate filesystem for the guest.

So why would you want to use a technology like LXC instead of a full system virtualization platform like KVM or Xen? LXC has several advantages: For one thing, it has virtually no overhead, and it provides a degree of flexibility because of its ability to share resources between
different LXC guests. (I know, these seem counterintuitive because the goal is to segregate them from each other,) Also, LXC supports not only virtualizing a running instance of an operating system (more on this later) but also individual applications, for which devoting an entire virtual machine is overkill. To see a good example of this, you can read more about what Google is doing with ChromeOS [3].

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