Dmitry Kharlamov

End User Desktop Virtualization on Ubuntu Linux

2010-07-19T21:24:00.003+04:00

Yesterday I've encountered a small dilemma. Few days ago I decided to dump Windows 7 because my Huawei E1550 was not working properly with it and to move to Linux. Another thing that tipped me into doing it was the fact that I could use Xen to run both Windows and Linux simultaneously (I am sick of VMWare because of how slow and limited it is and because of it's price). So after a few days of playing with Ubuntu 10.04 (in which my modem just worked out of the box...almost) I was ready to virtualize!

But that's when had faced the dilemma - which virtualization solution to use? There are Xen, KVM, Virtual Box, QEMU to name the more successful ones. I had to do a bit of reading to decide. To be honest, there is not much information on the topic of comparing all the above virtualization platforms. There is a good source, however, which is Virtualization.Info site, possibly too complex to digest for an average end user though. I also found an article by Joe 'Zonker' Brockmeier titled "KVM or Xen? Choosing a Virtualization Platform", which basically just calmed me down a bit as I was kind of frustrated over the complexity of information available on the net in regards to the topic. Then I searched for some guides on installing any of the solutions on Ubuntu and here is my conclusion broken down:

Xen
There is controversial information in regards to Canonical dropping support for Xen in favour of KVM, which was quite upsetting. But as Canonical say - "Intrepid runs a linux kernel version which Xen doesn't explictly support, and so the Ubuntu kernel team would have had to forward-port the Xen patches from 2.6.18"
There are however good guides on setting up Xen on Ubuntu.

I decided Xen was too sophisticated to just run some Windows Apps. Xen is more of a hosting solution successfully employed by AWS for example. So I decided to find out why KVM was so great.

KVM
KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux. It's built into the Kernel as a module and makes use of virtualization extensions found in modern processors. So it's quite fast! But again, quite difficult to set up. There is a good guide for Ubuntu - https://help.ubuntu.com/community/KVM.

QEMU
I can't really say anything about QEMU to be honest. I only know that it is the base for both Xen and KVM. WindowsXPUnderQemuHowTo is probably a good HOW-TO for Ubuntu.

VirtualBox
A great product supported by Oracle. From what I've heard it is lighting fast and far better than VMWare for a fraction of the download size. There is a version in Ubuntu repositories, which is Open Source but does not support USB. You can also download a free version for personal use from Oracle, which will support USB. According to this article it is also easier to use for a average end user. And this is the solution I went for using a very good guide for setting up VirtualBox on Ubuntu. Don't forget to install Guest Additions, which is basically kind of the same with VMWare Tools for VMWare.

Conclusion
I barely touched on the surface of choosing the right virtualization platform for your need topic. Yet, I am very happy with how well VirtualBox worked for me and with its performance. So, I suggest you go with it if you intend to run another OS along with your primary one, which should be Linux :-) I am also interested in using any virtualization solution suitable to run OSX, so if you have any information about that - let me know.

3D
As a bonus here is some information on running 3D applications on your virtual guest - Full OpenGL 3d Acceleration.

javax.naming.NameNotFoundException: name_of_your_resource

2009-11-11T18:55:00.001+03:00

Don't forget to include jdbc for your jdbc resources.

Dependency injection in javax.faces.validator.Validator

2009-11-09T18:27:00.002+03:00

Using no additional frameworks (Seam for example) it's impossible to @EJB in Validator. Let me know if I am wrong.

My workaround is based on a question, why bother? Just provide a validation method on a managed bean.

jQuery and JSF

2009-11-09T18:24:00.001+03:00

JSF appends parent ID to child ID.


<h:form id="form">
  <h:inputtext id="input" />
</h:form>

input is then rendered with id form:input.

That's actually nice, but jQuery doesn't understand $("#form:input") - doesn't like the colon and throws an exception.

Workaround looks like this - $("[id=form:input]").

Generics and getResultList()

2009-09-21T17:16:00.005+04:00

So, this is a common problem with a dirty workaround.

If you try

public List<YourClass> getAllResults()
{
  return entityManager.createNamedQuery("YourClass.findAll").getResultList();
}

You get this:

found   : java.util.List
required: java.util.List<YourClass>
    return (List<YourClass>) entityManager.createNamedQuery("YourClass.findAll").getResultList();

or if you haven't compiled with -Xlint:unchecked, this Note: YourClass.java uses unchecked or unsafe operations.

The issue is described here

Detecting Errors From Request Processing in JSF Pages

2009-09-19T19:45:00.000+04:00

Recently I came across a little problem — display a portion of JSF only if the request was successful, i.e. no validation errors and if the request has actually been sent to the server (no request, no errors). Here is what I did:

<h:outputText
  rendered="#{empty facesContext.maximumSeverity && !empty Enquirer.name}"
  value="Thank you. You message has been sent."/>

The source that pointed me in the right direction.

JSF + Managed Beans + Managed Properties

2009-09-19T19:34:00.001+04:00

I have stumbled upon this article (by Chris Schalk)while trying to remember what <managed-property> meant in faces-config.xml.

Very interesting and useful when you're developing JSF backed by EJB3.0.