would i be able to get a copy of that script from you, coz i'm too lazy to write my own?

Is there a good "getting started" type howto out there? More and more I need something like xen but I haven't been able to get it running on my debian testing machine.

Without a doubt, I completely agree.

About six months back, I needed to test out some stuff at work, and I only had one machine available to me. I'd been hearing some neat stuff about this "Xen" thing, and decided to give it a shot. Not only did it work perfectly, but word got around, and within a week it proved itself so well that management approved a new server to act as a dedicated Xen server, with a crapload of RAM (4x our "standard" order) in order to run multiple instances for the developers to test on.

I've since moved a couple of my home machines to Xen setups, too. It's just too cool, and *so* useful!

I really hope Red Hat's (and others) push to get it into the kernel proper pays off, and it gets integrated soon. Either way, with the latest Fedora Core supporting it, I'm guessing the next RHEL will include full support for it. (I'm only mentioning Red Hat as much as I am because it's our standard platform at work, and despite my best efforts, will remain so.)

it sounds really cool, but i really can't think of a use for it for me.

at work we're about to upgrade our servers to multiple cpus and many gigs of ram, they'll be needed by mysql/whatever, rather than separating things into virtual machines..

then again, i don't use linux on workstations, and tend to avoid installing things that aren't in yum, which is probably where the "i want to avoid hosing my system" would come into it.

Have you tried setting up read-only mounts to share the OS across VMs?

I hate that. We do that with our web farm, PXE booting with a shared NFS root. Each machine has its own /etc, /var. But if a Debian package is installed on the NFS server's root (in a chroot), each actual web node doesn't get the postinst configuration.... management hell, sometimes. Certain packages work, but others which need to touch /etc and /var don't.

Sounds like a problem that needs a clever solution. :)

arrgh- now i'm reading the Xen docs (again) and wheels are turning-

anyway- from the docs: "Note that the Linux NFS root implementation is known to have stability problems under high load (this is not a Xen-specific problem), so this configuration may not be appropriate for critical servers."

I understand you don't like it in that pkg-mgmt sense, but stability-wise, no problems related to NFS-root? I wonder what is meant exactly by "high load"-

If you export as read-only there's very little that can go wrong, except for the NFS server blocking.

Oracle Cluster Filesystem has this totally rad thing called Context Dependent Symbolic Links. Basically it means that you can have a shared root but certain individual files/directories can be mapped out to unique/local versions for each box in the cluster. It's designed for shared root Oracle installations, so it's fast as. It's a nice alternative to NFS that still allows you to do live Xen migrations. You've read about that i'm sure.

Also, unique var/etc is masochism. You only really ever need a few files/directories in etc and var to be unique. You can have these in a /local tree, then link to them from your shared /etc and /var.

I can't stop talking about how cool Xen is.

Try out a new program? Use a whole new operating system... a new operating system (Debian sarge) only takes 114 MB, so why not?

Why not? Doesn't Xen require modifications to the OS (unless you're running an Intel chip with VT)?

Needing modified guest OS'es or special hardware makes Xen a cool, but unsuitable replacement for VMware. It'd be cool if VMware came out with a VMware-based hypervisor product: boot into VMware, run unmodified guest OS'es underneath it, on any hardware.

I can dream, can't I? :-)

Xen 2.x requires a paravirtualized kernel, but not userland. And since I almost always run with a hand-made kernel anyway, typing ARCH=xen when building isn't a big setback.

Xen 3.x can run unmodified guests with VT chips.

VMWare is making new versions that use the VT stuff, I believe.

yep, that's cool.

Someone needs to spend time making a xen-oriented linux distro, built around concepts (and scripts) like that. Xenbuntu!

Heh, I have a script like that... my secret weapon! I'm currently writing an app that lets you take stuff you try out in a Xen instance and make it into a template you can later run basically by replaying your (edited, and documented) changes. For instance, set up a Hula instance by providing a variable for hulasetup. My idea is for it to make build testing insanely easy, and also yeild unit tests that can automatically determine if a server is doing its designated function properly.

I'm in the midst of making my CV hardcore for scrutiny by your crack team of HR people. Oh yeah, CV means Resume. Having never applied for a job in America before, I'm not really sure what you guys expect. Basically I am just writing about all the cool stuff I've been doing, what else should I put in?

Not at all related to this post, but *someone* who uses Xen needs to read it:

http://www.dtecomic.com/?n=382