Linux Gains Two New Virtualization Solutions 170
An anonymous reader writes "The upcoming 2.6.23 kernel has gained two new virtualization solutions. According to KernelTrap, both Xen and lguest have been merged into the mainline kernel. These two virtualization solutions join the already merged KVM, offering Linux multiple ways to run multiple virtual machines each running their own OS."
Re:lguest doesn't need VT (Score:2, Informative)
Re:Multiple ways to run Multiple OSs (Score:4, Informative)
I used to work for a search engine company (not Google) that has thousands of linux servers. After doing a bit of research they discovered that the vast majority of these machines are idle for a good amount of time. Rather than buy new servers they simply installed Xen and intellegently divided up the physical hardware to perform their different tasks. Now instead of separate physical servers to do web spidering, data analysis, log processing, etc. they've combined these tasks onto the same physical hardware but kept them as individual virtual servers.
Re:Why? (Score:4, Informative)
That said, you mentioned KVM.. KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). (from here [qumranet.com]). It *is* a hardware driver.
Re:Wireless card??? WTF? (Score:2, Informative)
If you NAT your VM network traffic, then things work (well sorta, with all the nastiness that NAT comes with).
Re:does anyone actually use a VM.... (Score:3, Informative)
Re:Why? (Score:1, Informative)
KVM allows you to virtualize any PC OS, as long as you have a VT CPU. lguest allows you to run another copy of Linux. Xen sits somewhere in the middle - you can run any Xen-compatible OS, not just Linux, but you can also run normal OSes if you have a VT CPU.
Xen is hardly lightweight. It's really suitable for servers, but it's too intrusive for general use. KVM and lguest, on the other hand, are pretty unintrusive, don't radically change the system, and can simply be used by regular applications. And their functionality doesn't really overlap.
Users will never see them anyway. Now they're part of the kernel, users will just see a program that makes use of them.
Re:Wireless card??? WTF? (Score:3, Informative)
This [launchpad.net] is the Ubuntu bug report (note the length and number of duplicates) which actually breaks apt on installation, but it's not Ubuntu specific; you can't configure it manually with this wireless card either. The only solution is to disable networking virtualization, which means I can't even have VMware use my wired connection unless I disable the wireless card entirely or physically remove it from my system.
Was I seriously modded down for that? Mods, what the hell?
Re:Could somebody clear this up for us? (Score:2, Informative)
Re:As a testament to my lack of knowledge... (Score:3, Informative)
Then there's para-virtualization.. modifying the kernel of the guest OS so you don't even need anything in the kernel. Well, sometimes kernel support can help para-virtualization
Re:Why? (Score:2, Informative)
Re:Very fishy and intriguing (Score:3, Informative)
Re:GPU support question (Score:3, Informative)
Probably the first thing they'll do is make it so X running in a virtual machine can share the same DRM (Direct Rendering Module) as X running on the host. Of course, that's not much good to a Windows guest.
Re:does anyone actually use a VM.... (Score:3, Informative)
I have vmware installed and use it on a regular basis. Here's what for:
I've talked about it elsewhere, but I also envision a system using UML (or now, lguest) to separate servers (or groups thereof) away from the main system to reduce security risks. It would let you use selinux with a fairly restrictive policy on your controlling system, and if one of the subsystems is compromised it could easily be discarded and rebuilt.
Clarification of these technologies (Score:5, Informative)
Xen - the Linux kernel supports code allowing it to be run as a guest underneath the Xen kernel, all through software. Linux's support for Xen does not make Linux a virtualization platform, only a GUEST for the Xen kernel which sits at Ring-0. (though a "dom0" Linux system can interact intimately with the Xen kernel, it actually sits at Ring-1). I should note that the Xen kernel also supports hardware virtualized domains, though this is unrelated to the patches to Linux.
KVM - the Linux kernel supports virtualization of guests through hardware extensions, this requires supported hardware. Linux becomes the Ring-0 kernel.
lguest - (my understanding is) an unmodified Linux kernel can act as a hyper-supervisor through loading Linux kernels as modules. Linux sits as both Ring-0 (supervisor) and Ring-1 (guests). This is experimental with limited features and only supports Linux guests.
UML - the Linux kernel becomes a userspace program. This allows Linux to run as an executable application/program. With UML, Linux can be compiled for a Linux or Microsoft Windows target. The executing OS sits at Ring-0 and the UML program sits at Ring-1. This has the advantage of requiring no modifications to the host OS and is very portable (you could email an entire Linux system to a friend without requiring anything installed to their system), but the disadvantage of poor performance.
From a high-level, the products UML, Xen, and lguest are actually very similar in function. They act as architectures to which Linux can be compiled in order to make it a guest OS of another Ring-0 kernel. These architectures provide the targets of a kernel module (lguest), a userspace program (UML), or a xen-domU guest (Xen). On the other hand, KML is the only patch that is intended to add support to Linux to act as a Ring-0 kernel on behalf of guest systems -- and even then, KML can be viewed more as a hardware driver for the processor extensions.
Re:Why? (Score:1, Informative)
Re:Could somebody clear this up for us? (Score:5, Informative)
They each fill very different niches, so there are very good reasons for having all 3 in the kernel.
Re:Clarification of these technologies (Score:5, Informative)
The UML program sits at ring-3 on X86 machines: it's just a normal user program using the ptrace() mechanism and extensions [except when the host has been patched with SKAS, but even here it's just a "normal user program". Rumor has it that SKAS might eventually make it into mainline, but it's time in 'real soon now' is starting to rival Duke Nukem Forever's.]. Rings 1 and 2 are odd, rarely used (IIRC there's the current virtualization craze and OS/2 as notable consumers) features of the x86, derived from MULTICS. For processors with only two (user & supervisor) modes, identify ring 0 with supervisor mode and the other rings with user mode.
It is a little odd to say that Linux "becomes" the Ring-0 kernel under KVM. It was already running in ring 0.
Re:So, will it run Windows? (Score:5, Informative)
You mean Lguest? FTA:
Lguest doesn't do full virtualization: it only runs a Linux kernel with lguest support.
So the answer is no, Lguest does not run Windows. Xen runs Windows, but only if you have a VT-capable processor. Like Lguest, Xen can run Linux without a VT-capable processor.
Re:Why? (Score:3, Informative)
Re:Why? (Score:3, Informative)
Only if enabled in the distribution. It doesn't harm anyone to have it available in the kernel source tarball. And both KVM and Lguest are implemented as modules, so if you don't load them, they aren't there.