I'm using a Xen Virtual Server to provide my Linux students with their own machines with admin rights. This has prompted interest in Xen from a lot of people just starting out in Virtualization. Following is a quick explaination of Xen and how to get a Virtual Machine up and running as fast as possible.

Hypervisors

Xen is a hypervisor meaning that it runs above the hardware but below any OS. Traditionally when you "virtualized" an OS you'd have a computer that you logged into which you installed virtualization software on such as VMWare workstation or VirtualBox. With this software you'd start the Virtual Machine from it's GUI and install the Guest OS via CDROM. In this case you have a Host Machine (the real physical machine) and a Guest Machine (the virtualized OS). With a hypervisor ALL operating systems are virtualized. This might seem a bit strange or impossible but is very powerful and extremely effecient. The side effect is that Xen can be very complex to set up. Let me explain the Xen boot process.

Xen Boot Process

1. Machine runs code in Master Boot Record
2. Bootloader loads the OS kernel
3. Xen lodges itself in memory and loads the rest of the kernel in a Virtual Machine
4. The user logs into the first Virtual Machine and starts, stops and restarts the other Virtual Machines from there

The name for the first Virtual Machine is Dom0 - it's the privileged Domain so it has direct access to the physical hardware. All subsequent Virtual Machines that are started are called DomU - unprivileged Domains. To manage a Xen Virtual Server you log into the Privileged Domain (Dom0) and use various commands to administer the Unprivileged Domains (DomUs).

Two modes of Virtualization

Virtualizers work in one of two modes - paravirtualization or hardware (full) virtualization. The difference being that a paravirtualized DomU OS knows it's being virtualized and has extensions to allow and assist in this. Paravirtualized Operating Systems are very fast and effecient. However there are times when you won't be virtualizing an OS that has these extensions such as Windows. In this case you need to use a CPU that has hardware vitualization support and run Xen in HVM (Hardware Virtualization Mode).

Paravirtualization:

• Runs on a lot of hardware - x86, x86-64, Itanium and PowerPC 970 with or without hardware Virtualization support
• DomUs can be Linux, NetBSD and Solaris
• Very fast

Full Virtualization:

• Requires Intel or AMD cpus with Virtualization Support built in
• DomUs can be most any unmodified OS including Windows
• Not so fast

To get around the speed issues with Full Virtualization there are paravirtualized drivers that have been written for many Operating Systems including Windows for disk access and network cards. This allows Full Virtualization to reach the speeds of paravirtualization in these two areas without requiring further modification to the Operating System. The Linux KVM Hypervisor runsin Full Virtualization mode all the time and thus needs paravirtualized drivers.

A lot of this tutorial was stolen from the CentOS wiki - http://wiki.centos.org/HowTos/Xen/InstallingCentOSDomU. I've shortened it by quite a bit to make it easier.  I assume you know this already but you will need to be logged in as root or have root privileges in order to execute this tutorial.

Creating an Image

The first step is to create an image that will hold the domU virtual disk. Since this can just be a file filled with zeros, our usual friend dd comes in handy.  The following command will create a /srv/xen/centos5.img file of 11GB, although the actual data blocks are allocated in a lazy fashion meaning that the disk image doesn't actually take up the whole 11GB until you fill it up. This is referred to as a sparse file.

dd if=/dev/zero of=/srv/xen/centos5.img oflag=direct bs=1M seek=10240 count=1

1. First we need to add the YUM repository holding the updated Xen. You will need to be logged in as root to carry out these instructions

wget http://www.gitco.de/linux/i386/centos/5/CentOS-GITCO.repo -O /etc/yum.repos.d/CentOS-GITCO.repo

2. Uninstall and reinstall the Virtualization group

yum groupremove Virtualization
yum update
yum clean all
yum groupinstall -y Virtualization

I was updating a CentOS OS and I noticed that one of the mirrors it chose was mirror.facebook.net so out of curiousity I put that into my browser and this came up. Does Facebook have extra bandwidth and storage they don't know what to do with?

Watching the compact high quality camera market is like watching a boxing match. It used to be Canon and Nikon in the ring until Nikon tucked it's tail in and ran. Panasonic promised to take the crown but after releasing the Lumix LX1 and Lumix LX2 people almost stopped listening to them because the photo quality was so poor. They came back with a knockout with the LX3 and turned out a camera with absolutely wonderful photos and low light performance in addition to it being very compact (more so than the Canon G10). A bit of history is probably in order. Canon had the G series which slotted nicely between the point and shoots and the DSLRs with full manual control, articulated screens and a bunch of other goodies. They also had a camera that slotted between the G-series and the point and shoots again - the S series. The S series had the G series' large sensor, a wide angle lens, manual controls and came in a much smaller body. It wasn't as nice to hold or use because it was compact but the quality of the photos were great. Canon cancelled the S series when the G7 came out thinking that the market was getting pretty crowded and Nikon had been K.O.ed in the 5th round anyway. The one thing I like about competition is it makes companies get off their collective arses and do something. The Panasonic LX3 takes photos as nice as the G10, has all the controls of the G10, has a faster lens (but less zoom) and is about half the size of the G10. Smaller is better in my book since I like to keep my camera in my pocket so Canon as turned the way-back machine to 2003 and reintroduced the S series and at the same time the G11 is a bit bigger and has the articulated screen again. The S90 will duke it out with the LX3 and the G11 will be for a different customer, one that wants more physical controls, an articulated screen and more zoom.

I've been a maemo MID user for several years and when I bought my Nokia n800 I was amazed at how easy wireless networking and bluetooth were. At the time Linux was very difficult to setup in this area. Times have changed and the Maemo OS has pretty much stood still. Each successive release we got a new set of bugs and not much else. Things have gotten slightly more stable but for the most part the n800 is underpowered and the UI is aimed at desktop users but with a 4 inch screen. The new Freemantle is supposed to be a drastic change from the past and by this video it looks like it. From the beginning Nokia wasn't committed to the Linux based mobile Internet devices and put all of their resources behind the Symbian OS they own and the Linux OS always seemed more like an experiment than anything. I guess the experiment is over because they've done a ton of work on Freemantle. I've read that it's the first of the next gen Linux MID OSes but it isn't the final one. Freemantle will have a GTK gui and the next one after that will be QT which Nokia now owns. The one improvement that I think they need is to stabalize the software. I don't know if a Communist/Apple approach is best but you have to admit that iphone apps generally work and maemo apps don't. Anyway check out the video.

It looks like the Freemantle version of maemo that the new n900 is using is much nicer and more finger friendly than the Diablo that I'm running on my n800. As much as I like Linux I've always thought that the Bora/Chinook/Diablo line of the Maemo OS were very crude and not always stable. It's funny that when I got my n800 I thought it had the slickest wifi and bluetooth configuration of any Linux OS but now times have marched on and my frequent lockups and applications that don't work have gotten on my nerves. Granted I'm using my n800 for way more than what it was designed for. Also Nokia has never been serious about the Maemo devices. It's largely been a community run project with Nokia making the hardware. The freemantle OS and n900 seem to be a break from that trend. I predict (and you can quote me) that at some point Nokia will be making more Linux devices than Symbian.

All I want is food with flavor, is that too much to ask? If I eat cheese it has to taste like something (Kraft are you listening?), if I buy ice-cream I want more than different combinations of the same 4 flavors, I see no reason why Pizza can't have more than one type of sauce and 5 toppings. And the point of this article - if I eat stuffed pasta the filling should serve a purpose other than to keep two pieces of dough from sticking together. There's a restaurant in Modena Italy (home to Ferrari) that serves a butternut squash ravioli in pistachio cream sauce that's supposedly divine. I say supposedly because I've travelled to Modena twice just to eat that dish and both times the restaurant was closed. Yes, that's a true story. This brings me to the present  time and I'm still chasing this grand idea that stuffed pasta can have flavor and not just the Robin to the sauce's Batman. Pumpkin puree and Butternut squash are both seasonal so taking a page from The French Laundry's list of tricks I've been using sweet potato. The French Laundry if you don't know is a wonderful French restaurant in Napa Valley California owned by Thomas Keller, one of my favorite chefs because of his philosophy on food. He believes that the first bite is wonderful, the second is similar and by the third bite your mouth is bored so there's no reason going on. So at the French Laundry you only get the first couple of bites of a lot of dishes. He keeps you in this "Oh my God" stage throughout the entire meal.

Anyway back to pasta. I don't like sweet potato pasta nearly as much as butternut squash because it doesn't have that bright flavor of squash nor is the flavor  as mallable because it takes too long for you to make it taste like something else than sweet potatoes. But having said that it's much easier to work with because the water content is significantly less making a firmer filling. With butternut squash I aim for (imagine if you will), bright orange flavorful meat with a touch of cinnamon, a burst of fresh shaved nutmeg and  a dash of grade B maple syrup. This makes a very flavorful, pretty and not too sweet filling for a ravioli and provides quite the visual punch in a green pistachio creame sauce. Alas, the sweet potatoes are an imposter but unlike the squash are available year round. Also even the worst sweet potato filled pasta is better than the best you can get from the store.

Most people don't make pasta because it takes too long or it's too difficult to work with. I have a few tricks which I'll share with you that may change your mind. By myself I made 100 ravioli (about 4lbs) in about an hour (plus an hour to bake the potatoes during which I watched a movie). If you have two people working - one rolling dough and the other stuffing you can double that number. This ravioli would cost you about $25 in the store ($2.50 homemade) so maybe it doesn't pay off but the quality is better. It's imperative that you have a powered pasta roller like the attachment to Kitchenaide's Mixer line or you have a second (or third person) hand cranking. Rolling the dough even with a power roller is the most time consuming part.

So on with it. I bought several Ravioli forms from Amazon (see the picture after the link) but what's funny is that I don't use them as they were intended. The idea is that you roll out flat dough, lay it over the form, push down with the plastic insert to create the indentions, fill, cover them with another layer of rolled out flat dough and finally seal the whole thing by rolling over the whole thing with a rolling pin. This sounds like a great idea but gets very messy with the sauce not going where it's not supposed to and it's almost impossible to avoid air pockets. If you prick the air pockets you end up with ravioli full of water when you cook it. So I take the plastic inserts, fill them with filling and throw them in the freezer for a few minutes. The result is little squash or potato ice cubes which I then lay flat surface down on the dough and fold over another layer, seal it and cut them manually. This ends up being as fast and I have more control.

A lot of people use egg wash to seal their pasta which also is messy. I have not found that it's necessary and if you're rolling your dough as you use it you don't even need water. Just dust your area with flour, roll the dough, place filling flat side down on the dough and fold it over to cover it up. Press long the edges to seal and cut them. Now take them and freeze them for cooking later. I even freeze them if I cook them immediately as it helps them hold together.

Ingredients:

• flour
• eggs
• sweet potatoes
• cinnamon
• nutmeg
• maple syrup or extract

There's one thing that I like about where I'm living - fruit grows. I have grapes in the front yard and Blackberries in the back. The grapes need to be tended too otherwise the fruit never grows but obviously because of the weed status of Blackberry bushes I have to do nothing to keep them alive. The grapes aren't quite ready yet although I did eat a few today. The Blackberries have been ripe for a couple of weeks and currently I'm pulling about 2 lbs of berries off the plants in my back yard per day (which equals 5 half pints of jam). That 2 lbs has been put to good use by becoming Jam and Syrup. So far the jam has been good and I  only say good because of it being compared in my mind with the Blackberry syrup which is wonderful. After I harvest tomorrow I'll make Blackberry jelly. Even though I've only given the Blackberry Jam a "good" rating it's heads above the stuff you get in the store.

I love Blackberry Jam but after cooking the berries down and straining them for syrup the juice was so pretty that I can't resist making jelly too. I use no commercial pectin so the ingredients list goes something like this - Blackberries, Cane Suger. The recipe for syrup is way more complicated - Blackberries, suger, lemon juice, vanilla. I like the syrup so much that I may use the same formula to make the jelly but throw an apple core in a cheese cloth bag in there to provide the pectin. Also I picked them a bit firm so I can capitalize on the extra pectin that pre-ripe blackberries have.

After I have enough jam and jelly to last the winter I'm going to turn my attention to Blackberry Vinaigrette and if the season lasts long enough I may try my hand at Blackberry Wine that I see at the Ballard Farmers Market. The wine will take about a year to rack and age so I'll be able to use it this time next year. Two days worth of berries will make one 750 ml bottle of wine. What I really have in mind for the wine is to make full bodied Blackberry wine reduction sauces for duck and steaks.