xenophobia

buffalo buffalo buffalo buffalo buffalo buffalo buffalo.

Fri, 03 Oct 2008 04:21:37 -0800

So. A new job, a move in progress, a bike accident, some replacing of laptops -- I don't even know where to begin.

But now I am trying, really I am, to get back into writing. I've put it off for the last few weeks. Haven't had the space or time. But now I've got to pay the piper.

I mean, this thing is getting uncomfortably official. You know it's on NSP's website? True story.

Chris got run over by a bus

Sat, 27 Sep 2008 21:45:02 -0800

Well, to hear him tell it, that's not quite what happened. The details are understandably fuzzy, however, a bus and his bicycle, apparently, attempted to occupy the same space at the same time. Chris assures me that he is ok, however, the two laptops he was carrying are now toast, and so chris is offline for at least the weekend.

another milestone.

Mon, 15 Sep 2008 11:06:50 -0800

So it finally happened.

After printing untold thousands of pages, Luke ran out of toner. I am assured it was glorious, or at least that's how I imagine it.

more editing.

Wed, 27 Aug 2008 10:10:16 -0800

I do so love copyediting. I must, otherwise I wouldn't do so much of it.

still hate openoffice.

Tue, 26 Aug 2008 11:29:55 -0800

Damn, blast, etc. Looks like a few days' worth of changes didn't get saved somehow. In fact, I've got no evidence they were ever made at all. I mean, I remember making them, but that doesn't really do me much good.

*sigh* Next book (if, not when) is going to stay in plain text until it hits the prepress dudes.

pursuit of instability.

Sun, 24 Aug 2008 14:54:25 -0800

So Solaris 2008.05 integrates a version of Xen capable of 32-on-64-bit operation, which makes one section of our chapter on non-Linux systems obsolete. (That being the section where we advise users to download the Xen binary distribution for a convenient 64-bit kernel image.)

Personally I'm glad of it. One can see, very clearly, Xen making its way from a loose blob of bits to an actual product. Eventually the struggles we had will be not worth mentioning, the sort of barbarism one doesn't bring up in polite company.

Or, as Luke is fond of pointing out, "Hey, Xen works now! Let's play with KVM."

terminal mismatch! how retro!

Sun, 24 Aug 2008 06:58:11 -0800

Pygrub will complain and exit if you try to use an unfamiliar terminal type. The symptoms are that, rather than showing the familiar GRUB-ish menu, Pygrub will exit immediately with errors like these:


Using config file "/etc/xen/test".
Error opening terminal: rxvt-unicode.
No handlers could be found for logger "xend"
Error: Boot loader didn't return any data!
Usage: xm create  [options] [vars]

And, of course, the domain won't start.

One solution is to symlink rxvt to /usr/share/terminfo/r/rxvt-unicode, thus:

ln -s rxvt /usr/share/terminfo/r/rxvt-unicode

Alternately you could just copy your own rxvt-unicode terminfo file to the remote machine, e. g.:


scp /usr/share/terminfo/r/rxvt-unicode user@remotehost:.terminfo/r/rxvt-unicode

xc_dom_find_loader: no loader found.

Thu, 21 Aug 2008 16:18:57 -0800

New error message for the index:

Error: (2, 'Invalid kernel', 'xc_dom_find_loader: no loader found\n')

The unformatted output is truly striking.

Anyway, this error occurred when I tried to load a kernel that wasn't Xen-aware -- I was just curious to see what the exact message would be.

silly pygrub trick.

Thu, 21 Aug 2008 03:04:39 -0800

Okay, this is actually pretty cool. You can provision a few distros pretty easily via Pygrub -- here's the relevant config (bootloader and disk line) that I've been using lately:

bootloader = 'pygrub'
disk = [
'tap:aio:/opt/xen/opensuse-10.3.iso,xvdb:cdrom,r',
'tap:aio:/opt/xen/domain.img,xvda,w'
]

NOTE THAT THIS EXAMPLE IS ENTIRELY MADE UP! OpenSUSE 10.3 does not support this install method, as far as I can tell.

You can see that I'm defining two devices, one a CDROM and the other an ordinary Xen disk. Pygrub automatically mounts the ISO, pulls a kernel off of it, and boots normally -- and since the initrd tells it to go into install mode, that's what it does.

It even works with Solaris -- we just have to give the kernel and initrd explicitly:

disk = [
'tap:aio:/opt/xen/opensolaris-2008-05.iso,6:cdrom,r'
'tap:aio:/opt/xen/domain.img,0,w'
]
kernel = '/platform/i86xpv/kernel/unix'
ramdisk = 'boot/x86.microroot'

Note the Solaris-style device numbers.

Obviously this won't work with distros that don't ship a Xen-aware kernel on their installation media, but that's it's a nice trick for those that do. (I think that's . (Apparently this is one of the standard ways of doing things now! I'm so excited!)

still not really into pokemon.

Thu, 21 Aug 2008 00:25:06 -0800

Have I mentioned I don't really like Ubuntu? For some reason Xen's network-bridge script kills my networking, even though I'm connected just fine without. First let's discuss how I fixed it (since I like to cut to the happy ending whenever possible).

What fixed it eventually was adding to /etc/network/interfaces:

iface eth0 inet dhcp

This let ifup handle eth0. I'm not sure why the non-Xen kernel was able to deal with the absence of this line, or indeed why the Xen kernel wasn't. Perhaps it is a red herring.

Then I restarted network-bridge (with sh -x) and noted that its output was a bit more sensible, but I still wasn't connected. Eventually I noticed that I had two default routes, one via peth0 and one via eth0. So I ran:

ip route del default dev peth0

And I'm connected. Adding that last bit to a script, or hacking network-bridge's transfer_routes() function to figure out why it's leaving two routes and fixing it, would be pretty trivial.

on the versatility of network-bridge

Sun, 17 Aug 2008 22:59:16 -0800

Network-bridge, the default Xen network backend, doesn't care what sort of data it's sending -- as far as it's concerned, they're Ethernet frames. There's a special case for IPv4 and the antispoof rules, but that's it. Other protocols, like IPv6, will "just work," and there's no current provision for Xen to inspect packets. (Although it wouldn't be that hard to add, building on the IPv4 support.)

And if you want to spoof your Banyan VINES address, Xen will not stop you, or indeed even notice.

tell me about pv_ops.

Sun, 17 Aug 2008 21:23:35 -0800

I need to write a blurb about paravirt_ops and what that means for upstream Linux Xen support. I don't think there are any administrator-visible changes (other than possibly better distro packaging,) but I'm not entirely certain. (I also have no idea where it'd go, but that's another issue entirely.)

Part of it is just that any term thrown around on the mailing list so much has got to be important, right? Maybe someone should do a concordance script to find common and significant terms in mailing lists.

Sun, 17 Aug 2008 08:33:15 -0800

I think Xen's PCI passthrough support has been dramatically updated since we wrote about it previously. Accordingly, we too will update dramatically!

(A review: the PCI passthrough allows the administrator to forward a PCI device to a domU. Once upon a time it was necessary to boot with the PCI device hidden from the dom0 -- this may no longer be the case. Hard to say.)

Of course, if we had some VT-d hardware we could test that, too. *sigh*

Error: Device 51712 (vbd) could not be connected.

Thu, 14 Aug 2008 18:20:48 -0800

Our discussion of the "hotplug scripts not working" error makes me extremely unhappy. Now that we're running into the bug, I really want to narrow down the cause and fix it.

Of course, this is "really want" in the sense of "except that I can't seem to concentrate on anything at all, ever. It's very disheartening.

Even so, I've been working on debugging the problem. Initially I thought that the hotplug subsystem wasn't working. Some work with udevmonitor convinced me otherwise. Now I'm leaning toward the idea that Xen isn't firing the right events for some reason. The machine's been up for a while -- domain IDs are in the 300s -- so that's a plausible cause.

Also, what's with that device number?

mysterious stuff in the xen source distro.

Sun, 10 Aug 2008 16:11:21 -0800

Checked out the xen-3.2-testing.hg repo. Was considering xen-unstable, but it's too unstable for me. I wonder what the Xen uses openSSL and PAM for. It's probably related to the remote management and XenAPI stuff -- but it's hard to say.

Working on compiling a kernel the "ubuntu way." Just realized I need some kind of baseline, so I've also installed the Ubuntu Xen package. Time to reboot.