Windows as Guest in Linux with minimal Software

You have Linux (any distribution, commands below for Debian/Ubuntu) and need to do just one tiny thing with Windows? Therefore you don't want to install thousands of packages and third party packages?
Then follow this quick guide made out of 4 steps and one package you need to install!

Fist install the kvm engine typing this into a terminal:

$ apt-get install kvm

Afterwards change into the directory where you want your virtual harddrive image to be created. The next command will create a *.img file with a size of 8GB.

$ dd if=/dev/zero of=vm_disc.img bs=1024k count=8000

Once this is done, you can boot up your virtual "machine" for the first time - of course with the Windows Install CD "inserted" into your device:

$ kvm -m 2048 -cdrom Windows_XP.iso -boot d vm_disc.img

Remember that you might have to exchange the name of your install-cd image.
Reading the manual of kvm (terminal command: man kvm) I found some nice features like graphical output to a vnc stream, using a specific sound-card, forwarding usb devices,... I am always using following command to start my virtual machine:

$ kvm -m 2048 -hda vm_disc.img -vga std -soundhw ac97 -usb -usbdevice tablet -smp 2 -vnc :0

Afterwards I connect to the vnc stream (localhost) using the "Remote Desktop Viewer" application.
Source: http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/bin/

Have Fun!

VLC as DLNA Client on Linux

Since version 2.0 VLC is able to play content from a DLNA Server.

On Ubuntu it seems not to be working out of the box. The first challenge is to realize, that a probably installed firewall (eg. ufw) is blocking all incomming traffic, meaning the broadcast of the DLNA server is not seen.

Add a rule to the firewall, to enable incoming traffic on port 1900 UDP for your media-server IP.

Therefore you might want to use a graphical user interface like gufw installable either in the Software Center, or with the terminal: 

$ sudo apt-get install gufw

Afterwards VLC should be able to see your DLNA server, but when double clicking, it seems that nothing happens. But this is not true - if you look more closely, you will realize that you suddenly have a lot of wlan/lan traffic. VLC is syncing the database without any graphical feedback. This is not really user-friendly.

After some time (depended on the size of your database, so be patient...) a folder icon appears, double clicking on it takes a looong time again. This process without graphical feedback (again!) is finished when you see a triangle in front of the folder... YAY! 

Now you can browse your database and start a movie, songs and even look at images!

Have fun!

Save the environment AND your eyesight!

I have to read a lot lately and therefore I print out everything. I don't like to read publications, papers and other scientific stuff on the screen, as there is no easy possibility to take down notes, mark some lines and interact with this thing. I just like to work with paper and pencil!

To save the environment a little bit, I always print two pdf pages onto one sheet - double-sided of course - leading to 4 virtual pdf pages being printed onto one single sheet of paper.

This is awesome, but my eyes start to hurt after some time, because the text is so unbelievably small. However, I realised that there is a lot of white space on these sheets and somehow it should be possible to remove the white space and "zoom" the pages a little bit for a better readability.

Exactly this is done by pdfcrop (http://pdfcrop.sourceforge.net/)!

You just type something like

$ pdfcrop --margins 5 input.pdf output.pdf

into your terminal and then print the output.pdf as usual. You will realise that the font size has almost doubled (or sometimes even more), only with removing the white borders. Happy reading!

Switching graphic cards on the Thinkpad T400

I just realised that a lot has changed since I looked for support of Hybrid Graphics under Ubuntu/Debian a few years ago. Now, there is a project for switching between the integrated and discrete graphic card called vgaswitcheroo!

In the BIOS settings you have to select "Switchable Graphics" and the computer will boot up with the internal graphics card (in my case Intel 4500) turned on.
With one simple command, you can then switch to the discrete graphics (ATI Radeon HD 3400). The only expense at the moment is, that you have to log out and in again to restart the x-server.

To switch to the discrete graphic card open the Terminal and type:

sudo echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch

Then log out and in again. You can then check your running graphics card under "Details" in the "System Settings" (running Gnome 3.2 or higher).

To switch to the internal graphics type:

sudo echo DIGD > /sys/kernel/debug/vgaswitcheroo/switch

Thanks for this awesome tool!
Source: https://help.ubuntu.com/community/HybridGraphics

Do you want to automate things?

I created a shell script, which detects the running graphics card and asks you whether to switch or not!
Download it, make it executable and run it as superuser! I commented every piece of code to make it readable for you.
Download: https://github.com/j-4/scripts/blob/master/switch_graphics.sh

Have fun!

Most perfectly fitting Raspberry Pi Paper Case

Previously I downloaded the famous Punnet paper case (http://www.raspberrypi.org/archives/1310), but unfortunately it was not really fitting. The base area was too broad and the holes for audio out, HDMI and micro USB not properly placed.

Therefore I measured the whole Raspberry Pi in detail and quickly drew a case based on the Punnet, but without the annoying bugs.

You can choose which file to DOWNLOAD:

http://homepage.univie.ac.at/s.hammer/files/RPi_Case.pdf

http://homepage.univie.ac.at/s.hammer/files/my_punnet.png

http://homepage.univie.ac.at/s.hammer/files/my_punnet.svg

I think you are smart enough to figure out where to cut, fold and glue ;-)

The case has to be folded in a way that the lines are inside!

Keep in mind that you uncheck "Fit to printable area", and that you do not use scaling for printing.

Further, if you glue paper edges above the HDMI and the micro-USB plug, the board is even more stable in the case! There is no wobbling or squeezing (See photos for details).

Here some photos of the resulting paper case:

This case, as well as the all blog-entries, images,... are published under the Creative Commons License: http://creativecommons.org/licenses/by-nc/3.0/

So, if you still find a bug, just download the *.svg and fix it (or comment here)!

Android Camera App complains "Please insert an SD card..."

Today my Android phone running Oxygen Rom 2.3 could not make photos any more. A error message appeared on opening the camera app: "Please insert an SD card before using the camera", although the sd card was present and also detected by the system.

When mounting it on my Linux system, I could not delete any files and the error appeared: "read-only file system".
A little research revealed, my fat32 filesystem got corrupt somehow, but this can be easily fixed:

sudo fsck.vfat /dev/mysdcard -v -r

(please unmount the partition before and change /dev/mysdcard to the value of your device! you can see all your mounted partitions with running the "df" command!)

On Windows, there might also be a button somewhere saying "Repair File-System".
Mount SD card, boot the phone and it should be fixed!

Ubuntu/Debian: Bluetooth disabled by default!

I found this really useful post here: http://ubuntuforums.org/showthread.php?t=1333221
If you ask me, it would be best if GNOME remembered the last state of the devices across reboots.

"How to set bluetooth radio default off (after booting)?

As superuser edit the /etc/rc.local file add this line before exit 0:

rfkill block bluetooth

This will keep bluetooth turned off when you boot/login but you can still turn it on at will with the bluetooth applet in the panel!"

Please make sure rfkill is installed:

sudo apt-get install rfkill