Teemu's blog – Page 7 – Blog about anything (but not everything) I find worth mentioning

February 2, 2012November 3, 2015

Xen: Ubuntu 11.10 as Dom0 and DomU

After spending hours of figuring out how to get Xen virtualization on the latest Ubuntu done as simply as possible, here are the results. Hopefully they are helpful to you.

1) Install packages

$ sudo apt-get install xen-hypervisor-4.1-amd64 xen-tools

2) Reboot with Xen

Note that there will be a two-stage grub menu. First choose Xen, then choose the kernel from the second menu.

Press ESC during boot to see the menu in the first place if it is hidden.

3) Check that Xen (Dom0) works

$ sudo xm list
Name                         ID   Mem VCPUs      State   Time(s)
Domain-0                      0 15289     8     r-----    126.5

4) Fix xen-tools

$ sudo cp -R /usr/lib/xen-tools/karmic.d \
             /usr/lib/xen-tools/oneiric.d
$ sudo rm /usr/lib/xen-tools/oneiric.d/70-install-ssh

This is needed because as of today, the next step will fail due to some strange umount problem related to ssh. There is no need to install ssh immediately, as it can be done later from the console (step 7).

5) Create a virtual machine (DomU) running Ubuntu 11.10 amd64

$ sudo xen-create-image \
    --memory=1G --size=10G --swap=1G \
    --dist=oneiric --install-method=debootstrap \
    --dir=/home/xen --hostname=xen1 --dhcp

Configuration will be stored in /etc/xen/xen1.cfg, virtual disks in /home/xen/domains/xen1.

Write down the random root password from the installation report.

6) Start up the new virtual machine with console

$ sudo xm create xen1.cfg -c

You can exit the console by pressing CTRL + ALTGr + ‘}’

You can enter the console later with ‘xm console xen1’.

7) Update (and install) packages in the virtual machine

root@xen1:~# apt-get update && apt-get dist-upgrade
root@xen1:~# apt-get install openssh-server

8) You’re done.

To shut down the virtual machine from its (ssh) console:

root@xen1:~# halt -p

To later start the virtual machine:

$ sudo xm create xen1

November 12, 2011November 3, 2015

Twitter wins

Being using social media sites for almost 5 years now, I would say that Twitter will win.

Why?

The competition: Facebook and Google both make things too complicated. First of all, they don’t give a proper list of your own stuff where you could delete anything you have written earlier and don’t want to have available any more. Twitter has a single stream which has *everything*. You can delete anything and everything at any time.

Sometimes openness is best privacy.

We’ll see…

October 4, 2011November 3, 2015

A violin does not matter

I was about to go to sleep, but I couldn’t. Not after reading the latest stories of Ken Rockwell on my mobile phone. I had to fire up the laptop to be able to write this blog post.

Don’t get me wrong, I like Ken Rockwell’s blog, and I will continue reading it – mostly great stuff. However, it is sometimes irritating to read his analogies, like in the writing titled “If sharp lenses don’t matter, why do I talk about it?” on 3 October 2011. He claims “our choice of keyboard has nothing to do with what we have to say or the quality of the final result”, him meaning that it doesn’t matter what kind of lens we have regarding the final result. I am happy I can pick good information from among his sometimes provoking (and entertaining) writings, but I felt it is time to correct one recurring mistake he continues to feed to his readers. This misunderstood theme is also causing most flame threads in other photography sites when people have failed to find the good intentions of Ken behind his way of communication. Ken says “crappy camera can take good photos”, when he means “a pro with a crappy camera gets better results than a newborn with a D1s Mk4”. Most people don’t get this point at all.

Back to this specific case. First of all, the output of a keyboard is DIGITAL. The output of a lens is ANALOG. Digital means 1 is 1 and 0 is 0. There are no such things as a “good” 1 or a “bad” 0, when they are atomic parts of a digital file and not characters painted on a wall by an artist. Therefore, it truly doesn’t matter what kind of keyboard I used to write this this blog post. I decided to use a laptop for productivity and convenience, over using an Android phone with its touch screen — as Ken tries to point out. The characters you see on your screen depend on the rendering algorithm, your video card and the monitor. The message is the same. BUT, when I take a photo, a lens always makes a difference. It has analogue output to the CMOS of my DSLR, and the sharpness, colours, contrast, bokeh, all depend on the lens quality.

I agree with Ken that it doesn’t matter if I have a $10K lens yet I shoot bad compositions of no content and idea (this is what Ken tries to really say), but a lens can never ever be compared to a digital keyboard — the output is different between different lenses. A much better analogue would e.g. be to compare a great violin player using a crappy no-name violin and a crappy violin player using a Stratovarius. Which one would you rather listen? And only then you could truly claim and make other people understand that “a violin does not matter”.