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So, How’s Xen on Debian?

So, how many of you use Debian? I bet a lot. Well, here it is what the Debian Xen package maintainers told The Xen Project, when asked a few questions. We are talking about Bastian Blank and Guido Trotter. In fact, they share the burden, with Bastian doing “most of the work nowadays” (Guido’s words) and Guido “starting packaging Xen many years ago, while assisting with stable security updates lately” (ditto).

You’ll discover that they particularly like the Xen architecture, and this makes us really really proud. It also look like a shorter release cycle for Xen is in the wishlist. Well, Xen 4.3 cycle has already been way shorter than its predecessors, and the feeling is the future will be even better!

However, the most surprising thing is that coffee is quite unpopular with them too, as it was already the case for Maarten from Mageia… I am honestly starting to think whether this could be a ‘package maintainers’ thing’!

Anyway, sincere thanks to both Bastian and Guido for finding the time for this interview, and let’s get straight to their answers!

The Xen Project: What’s your name, where are you from, and where do you live?
Bastian: My name is Bastian Blank. I live in southern Germany.
Guido: I’m Guido, from Italy, and I currently live in Munich, Germany.

What do you do for living, and what is the distro you maintain the Xen package for?
Guido: I work for Google Germany, on the Ganeti project (a cluster virtualization manager that uses Xen or other virtualization technologies). I started the Xen package on Debian, and nowadays I mostly help with security updates.

Do you (usually?) spend your working hours in an office, or do you work from home?
Guido: I work from the office: they have lunch there! ;-)

Where do you get your daily caffeine intake from?
Bastian: I don’t.
Guido: I don’t have a daily caffeine intake: I sometimes drink coffee for pleasure, and most of the time I don’t.

Why Debian, and how did you get involved with it?
Bastian: Because it works. Debian provides a vast ecosystem for free software and I’m able to find almost any software I would like to try.
Guido: I started using Debian in high school, and became a developer about 10 years ago, during university. I love Debian because of its community, its values, and the fact that it just works better in my experience.

Why Xen, and how did you get involved with it?
Bastian: Some years ago, the whole virtualization stuff was at the beginning. I took a peak at VMWare, but it was a nasty software. Then I found Xen.
Guido: I read about Xen during university while studying operating system, and it seemed a very useful and exciting platform. I proceeded trying it out, installing it at ISPs I was consulting for, and writing my master thesis on it. Then I joined Google, where I worked on the Ganeti project, to provide a cluster-level virtualization environment based on top of Xen (and later KVM too).

What is it that you like most of Xen? What is it that you think is unique/distinguishing of it, wrt to other Open Source virtualization solutions? What is it (if any! :-P ) that you dislike most of it?
Bastian: Xen is the only Open Source tier 1 hypervisor in existance. It comes with some pretty usable control tools. However it often have problems
with new hardware.
Guido: I love the hypervisor “microkernel” concept, the fact that it doesn’t require special hardware to run (in paravirtualized mode), and the elegant design.
I hate to have to deal with different kernels in most cases, and that it’s not good to run on a desktop system.

Do you also use Xen for work (or leisure) and, if yes, do you use Debian and, hence, your own packages for that?
Bastian: Yes.
Guido: Yes, I have packaged Xen for internal use at Google as well, starting from my own packages, first for Ubuntu and then also for Debian. Nowadays I’m not responsible anymore for that aspect.

Do you have any, even very rough, idea of how many people uses Xen on Debian, which of course means how many people use your package(s)?
Bastian: The Debian Populary Contest provides some numbers for the minority of systems providing the information, we disable reporting of this
informations by default. It shows an installation count of 2600.
Guido: No, I have never posed myself that problem. :-)

How is your interaction with Xen Debian users? Do they regularly feel bug reports and/or get in touch with you in any way? If yes, what they typically say, do they have any recurrent requests or complaints?
Bastian: Our bug-tracker is the main tool for interacting with the users. The correspondence from the bug-reports and everything else goes to a
public mailing-list. A recurring complaint is the missing support for pv-grub and other mini-os stuff, which we can’t build for reasons.
Guido: Recently I mostly interact with developers that ask me how to add a patch, or with the security team. Normally I try to make sure they hare happy with the result of their inquiry.

How do you find the work of packaging Xen for Debian? Do you think it is different from packaging other pieces of software, and, if yes, why?
Bastian: Xen is a beast and the build environment is one of the worst I know.
Guido: Xen is different because of its “strategic” position in the system. It’s not “just a binary” or “just a library” so one has to be extra careful. Nobody likes an unbootable system.

What is the most challenging aspect you face (or have ever faced) regarding packaging Xen?
Bastian: Debian does not like opaque blocks of software, so we have to split libraries of the main package.
Guido: Sometimes there has been a bit of fighting on the lists. Plus the higher risk of breaking people’s system.

What’s your workflow like? For instance, when do you decide there is the need for a new package revision, or version? How do you handle new Xen releases, security fixes, and stuff like these?
Guido: When the security team advises me there’s a problem I evaluate the impact and then try to prepare an upload. Sometimes I have to ask for help to backport the code to the ancient version Debian stable ships.

Since you started being the Xen package maintainer for Debian, what has been the most notable Xen development related event that affected your work, either positively or negatively… I mean has there ever been anything that shook your workflow from the very foundations?
Bastian: There is an incompatibility in the xenstore communication between 4.0 and 4.1. Because of that, after an upgrade of the client library, all
privileged communication failed.
Guido: Probably not. I guess the best news is pvops and avoiding having to handle a very patched kernel.

How is it your interaction with the upstream Xen community? Do you usually find the help you need (if any) and, if no, what can we do for making things better?
Guido: The Xen community has always been very helpful and supportive. I’ve always enjoyed working with them. Recently we have cooperating also on non-Debian matters like organizing the Xen Hackathon in Dublin, and I got more involved with them.

Is there something you’d ask to the Xen Dev community –something like “please do”, or “please keep on doing”, or “please stop”, or even “please never start doing”?
Bastian: Please

  • do shorter release cycles (see Linux),
  • split the whole beast into smaller pieces that can and should be released independently (see Xorg) and
  • provide stable interfaces or use libraries to hide interface changes from the users.

Guido: Please keep delivering a great product? :-)

Are you a member of the Church of Emacs, or do you follow the Vim Heresy?
Bastian: I follow the Vim Heresy.
Guido: Vim Heresy, of course!

For getting in touch with you, what electronic channels (mailing list, IRCs, etc.) are the relevant ones? What about in person (conferences, etc.)?
Bastian: The easiest way to get in touch with me is using the mailing-lists. Ocasionally I attend conferences as time permits.
Guido: Email. Conferences (Debconf, FOSDEM, LISA, Linuxcon). On IRC if you ping me, and on #ganeti (freenode).


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Posted in Community, Xen Case Study, Xen Development, Xen Hypervisor.


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