KVM is one of those things I’ve kept an eye open for ever since I heard about it. First of all, I should mention that there is currently a great deal happening on the virtualization front, here’s a list of virtual machines to look over. What is more, it is not so much a wealth of competing products, because it seems that everyone has their own little twist on the matter, and none of these are completely equivalent solutions. There is a host of different terms to describe these techniques to boot.

I’ve known about VMware for 5-6 years, and that is how I originally started out playing around with linux in a safe and easy environment. Since then there have been many linux centric projects that have made waves at some time or another, not all of which I’ve tried. I think User Mode Linux was the first one I heard about. It ran a modified host kernel and could host multiple guest machines that would also be running a modified kernel. You could use it to host Virtual Private Servers, which has been common now for a while, but wasn’t all that common back then. You could also set up honeypots with them. There was also a VMware competitor called Win4Lin (for Win9x) which was like a poor man’s VMware. It would run fairly well, but it was far from being equally polished and feature complete. It also had the advantage of being strictly an application, no kernel hooks. A couple of years later there was a new project that was very loud, namely Xen. Xen is one of those odd projects that had a lot of potential and broad support, and yet didn’t quite have the kind of adoption one would expect. It was quite a complicated piece of code that required a lot of setting up and so on, but Fedora shipped it by default (I’m not sure if they still do) and it worked out of the box. Again it was a modified host kernel, but the guests could run completely unmodified. I’m not sure how recent this is, but nowadays Xen also runs various operating systems, although in some cases they need to be modified. Then there was CoLinux, which approached the issue from the opposite side of the table: Linux as guest. I never got around to trying it as I never had to use Windows for long stretches of time, but a lot of people (those poor souls trapped on Windows) were very enthusiastic about it.

So what about KVM? Well, KVM is interesting because of how “close to the metal” it is. Obviously, any kind of virtualization adds some overhead due to the unavoidable indirection. But KVM actually does not position itself above the kernel, as most virtual machines do, but uses kernel primitives to host guests (in fact it sets up a whole new kernel execution mode guest for this). It also uses cpu virtualization extensions (current Intel and AMD chips) to gain speed. All of this is fairly recent stuff, KVM was merged into the kernel for 2.6.20. So, of course, the major advantage of KVM is that it’s well supported and well tested in kernel mainline.

However, KVM is not a virtual machine in itself, in the sense of being a complete application. It’s more like an access layer which exposes a /dev/kvm interface. The way to run KVM is through QEMU, which is actually an emulator. I haven’t mentioned emulators so far, but they are in a sense the second type of virtualizer/emulator software. The difference is that a virtualizer creates a virtual machines with virtual hardware (eg. network adapter) for the guest operating system to run on, but the cpu is still that of the host. An emulator instead emulated the guest cpu, and therefore has to translate every machine instruction into a different one. This means that you can run say a powerpc guest on an x86 host. It sounds very cool, but it’s orders of magnitude slower, so it’s not as much of a hot topic.

But back to KVM. As I said, the application is still QEMU, but it’s accelerated through KVM. I had been looking forward to taking it for a spin, especially now that I also have an Intel chip with the virtualizing extensions. On Ubuntu it’s all ready to go, just install the userland applications from the repo (qemu and kvm) and you’re set. Qemu is quite nice and simple to use, but the combo is temperamental and unforgiving. You can set up your guest machine in 2 minutes, but with Windows I had quite a number of fatal crashes (Exception 13) that aren’t that obvious to figure out. Furthermore, it seems that even linux distros aren’t trivial to run on KVM/QEMU. In terms of a complete machine virtualization it leaves something to be desired. Notably, the video flickers quite visibly while running on a vesa driver. That isn’t to say that other virtual machines cannot or will not use KVM as part of their solution.

But for the time being VirtualBox (something of a lightweight VMware, which is also free software) is more convenient.

Disclaimer: This entry is something of a historical account of my exposure to virtual machines. I did not do any fact checking here, and the statements only reflect what I recall about the particular products.

So ogg is well known as the open format for audio and people seem to love it, it has broad support. To be precise, ogg is just a container format, so just the fact that a file is an ogg file doesn’t tell you much more about it than a zip file tells you about its content.

On the video side of things, noone seems to use ogg. Even though it is an open and by all accounts free format, I very rarely come across ogg videos. And sadly when I do, often they are broken. Since Theora seems to be the most used codec for ogg video, I’m assuming they’re all encoded in that format (I know I’ve never seen an ogg video not in theora, although I don’t make a point of checking).

Common symptoms:

• Timer is completely bonkers, saying a 20 minute video is several hours long and whatnot.
• Video stream has lots of bugs, frame freezes.
• Audio/video sync can be way off.

Case in point, download this video from Akademy. In mplayer and vlc alike the timer is confused, and the video stream freezes as well. This is the kind of problem I’ve seen a lot of times with ogg videos.

Now it may be a production mishap for this particular video. But I’ve seen these bugs with ogg a lot more than with other formats. In mplayer, even if you reindex the stream the timer still doesn’t get it right. It tells me the video is 412:29:15 long.

So what is it? Is ogg/theora busted or is the implementation busted? Is the encoder so bad that it’s impossible to produce a video without bugs? Or is the decoder buggy?

Yees yes, that fantastic game we played in the early 90s. Remember it? Of course, who could forget. Getting that prince unscathed through all those tunnels, traps and past all his enemies was great fun.

Ah, the days when Ms-Dos was our operating system of erm… choice and we gave the keyboard a good workout.

Prince of Persia kept reappearing in new releases, but as far as I’m concerned once you kill the classic 2D game play feel, it’s all downhill. The story lines for the later versions were also tediously complicated, nothing like the elegant simplicity of the classic. The original and the sequel, those are the two I played back then.

And now you can re-live the experience yourself. The Unofficial Prince of Persia Website has all the scoop, with plenty of extras. The oldest versions (1 & 2) are considered abandonware (which means no one is there to collect) and are up for download from the site. There’s also cheats and walkthroughs if you get stuck (ah, how much easier it is to play these games nowadays when you don’t have to figure it out yourself ).

Not only that, the walkthroughs for the sequel even have captures on google video, so you don’t even have to play it yourself.

“But wait a minute”, you say, “didn’t you say Ms-Dos? How am I going to play these games? I’ve moved on from Dos by now.” Funny you should ask. There is a Dos emulator called dosbox, which gives you a window into Dos, if you will. Inside there you can play any Dos game, and dosbox has a pretty long list of supported games.

Enjoy Prince of Persia!

This only affects you if you have some source of RAW images, typically a camera would be that source. Then the RAW images need to be post-processed (which of course is something that’s already done if you extract JPG’s instead of RAW images from the camera) and converted to a target format, like JPG.

Viewers/browsers

The best one I know so far is showfoto, a component of digikam. digikam itself is fussy about images having to be part of albums, but showfoto has an adequate image browser with exif data display and some statistics about the image. It’s also worth noting that digikam itself has been given a lot of attention, and has recently developed into a much better and more useful program than it was a few years ago.

Rawstudio also has a rudimentary image browser.

Converters

For this I would advocate ufraw. It’s a standalone program, but it’s also a plugin for the gimp. The interface is straightforward and quite handy.

showfoto/digikam also has features for conversion, but they are somehow tucked away in the menus and harder to find.

Rawstudio aims to be the tool of choice for this, but for the moment is seems rather immature and the interface could use work.

I think I read somewhere that Krita is supposed to convert its inner colorspace to be 16bit, which would make editing RAW images native, without needing to convert them first. That would be awesome. For the time being, I can’t say anything for Krita, because it crashes the moment I start it (probably a bug in the koffice ebuilds).

Status

So the support for RAW images is quite encouraging. Not as nice as in Photoshop CS3, and this applies principally to the conversion options and the types of adjustments that can be made, but decent all the same.

The Microsoft Intellimouse Explorer 3.0. Yeap, they may sell a whole lot of crappy software products, but this is one they really got right.

Best mouse I ever had. Before the optical age, mice would clog up with dirt and wear out. Well not anymore. I’ve had this one for a great many years, the longest lifespan for a mouse yet.

It’s so ergonomic that any other mouse feels totally alien and awkward. The only problem is that the wheel scrolls so softly that the threshold for scrolling a bit too low, and sometimes it skips on its own. So when watching a movie in mplayer, it will seek forward without being asked to.

But otherwise it’s perfect. Up to now. It seems the buttons are getting worn out by now, and sometimes one click registers as two. This isn’t uncommon with crappy mice, I’ve seen it before. But in this case a sure sign of old age. It’s time to replace this old trooper.

Any recommendations?