Dom0 Hypothetical Question about OS's

  • Hi All,

    As I learn more and more about XCP-ng (Xen) I find that I am very impressed with its capabilities.

    Lately I have learned that all of the DomU instances as well as even the Dom0 instance are VM's but that Dom0 is supposed to have elevated privileges to interact with the core hypervisor.

    I have also learned that the Dom0 OS is actually more like a native OS which talks directly to the hardware while other DomU VM's have virtualized hardware which I guess talks to the Dom0 hardware. It also seems that Dom0 can actually be Linux (one of the dialects) or FreeBSD types, but that got me wondering about a hypothetical possibility.

    With that in mind, I was wondering if, in fact, could the Dom0 OS actually be something like Windows or illuminos-based (Solaris) as an OS?

    Could it, actually be even some type of completely different OS and then what exactly are the specific requirements for Dom0 to host some type of OS and provide the needed functionality to the core hypervisor?

    Any thoughts on this?

  • XCP-ng Team

    There has been efforts to use Windows/Solaris/Any OS as Dom0 with help of HVM. You'd find some stories around internet for it.

    You should also look at QubesOS project.

    The last standing solution for Xen/XCP is CentOS as Dom0 with additional tooling.

  • XCP-ng Team

    What kind of need would this answer to?

  • @r1 Thanks and I'll dig around some more to see what I can find. Mostly just curious (also @stormi ) about the possibilities and what may, or may not, have been done towards this direction.

    Also, I do know of the QubesOS project but my project, although having some similarities is significantly different and more towards a Cloud based solution. 🙂

    Thanks again and have a great day

  • Technically, it's difficult, it can't something different than a Linux or *NIX system. Why ? Because, by default, the dom0 is a PV VM, that is something impossible with Windows, because you can't modify the kernel to bring the changes to be able to boot in PV mode.

    And I have doubt about the fact to control the Xen hypervisor from Windows (at low level).

  • XCP-ng Team

    @ruskofd Its possible to have HVM Dom0 thus enabling Windows/Solaris/Any OS as Dom0. The PV Dom0 concept was before Hardware Virtualization feature (vmx). Xen is old 🙂

    In fact, it was Intel working on this for some time. Dom0.pdf

  • @ruskofd Thanks and that is very interesting. I am looking it over now. Really appreciate the input. 🙂

  • @r1 Didn't know about the works on Dom0 HVM. But for now, I think most of the work on this is on PvH Dom0.

  • Hi All,

    In some of the latest read that I have been doing, it seems that the XenServer folks were also investigating the ideas of so called "Sub Domains" or "Driver Domains" via Mini-OS and MirageOS as minimal OS's to deaggregate Dom0 to take drivers out and make them independently sufficient such that if something happens to one of them then the rest of the system remains unaffected. This links into the ideas of Unikernels but I think that a lot of this is still in the R&D phase although some great ideas, to be sure.

    I could see a whole set of Sub-Domains to handle just about all of the functionality that Dom0 currently manages in perhaps a future evolution.

    Cheers 🙂

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