Category Archives: Linux

Kernel Panic

Recovering encrypted home folders in Ubuntu

Yesterday was my first day back in the office after a 6-months stay at UCSC and some leave and obviously my computer insisted on having a number of updates installed immediately when I got it started. A distribution upgrade to Ubuntu 11.04 was available, so I decided to go with that. After the download was done, and about halfway through the installation of the updates the computer ran out of disk space… and got completely stuck. Lots of I/O errors flooding the consoles, the installation process not getting anywhere, unable to open and close programs etc. I left the computer running, but eventually it crashed completely and rebooted. Next step was kernel panic… so it was time for a reinstall.

I booted into Ubuntu 11.04 Live from a CD and got access to the machine. Next step was to get the files out of my encrypted home folder. The home folder contained two files, a .desktop file and a readme file. The desktop file did nothing but make Nautilus complain about something untrusted and the readme tells you to run ecryptf-mount-private. That resulted in an error, basically saying that the home folder is not set up correctly, but no information on what is wrong, or how to correct that. Instead your left on your own. After googeling and trying several suggested solutions I found a method to get access to the encrypted folder. All you need is your old username and login password. No need for the encryption key / mount password.

First mount the partition with your home folder somewhere, for example in /mnt:

sudo mount /dev/sdXXX /mnt

Then move the existing home folder of the live system to somewhere else:

sudo mv /home /cdhome

Now make a symbolic link from the old home folder in the mount you did and to the root of the live system:

sudo ln -s /mnt/home /home

Then create a new user with the username that matches the username you had on the system with the encrypted home folder:

sudo adduser xyzw

and go through all the questions. Finally, su into that username:

sudo su xyzw

and with a little luck, you will be asked for the login password that matches the encrypted folder. That password is the last login password you had on the system the folder came from, not the password you just made when you created the user in the previous step.

ARToolkit problems with Ubuntu 9.10

In our project we have the ARToolkit installed on several machines, and not all machines have problems with the V4L version of the toolkit, so you could try out the V4L version before resorting to the GStreamer version.

If you encounter the following error: “error: acquireing channel(0) info” it probably means you should configure the ARToolkit for GStreamer. Apparently this is due to some problems using V4L2 libraries, which is not supported by ARToolkit.
To do this you should re-run configure and make in the root of the ARToolkit to rebuild the toolkit. It is important to remember to clean the previous installation before reconfiguring. This can be done by running “make clean” in the root folder of the toolkit.
When configuring select option 5 “GStreamer” and choose the rest of the options that are appropriate for your system. After compilation you should be able to run the “simpleTest” demo.

If the default options does not work with the simpleTest example, it might be necessary to specify some options before running the example. Try running the following command to set options for ARVideo.

export ARTOOLKIT_CONFIG="v4l2src device=/dev/video0 use-fixed-fps=false ! ffmpegcolorspace ! capsfilter caps=video/x-raw-rgb,bpp=24 ! identity name=artoolkit ! fakesink"

Remember to change the device string to point to right camera source.

Problems with Eclipse buttons in Ubuntu 9.10

Just found this post which deals with the exact same problem that I have been fighting with…

After upgrading to Ubuntu 9.10 (Karmic Koala) some buttons no longer work in Eclipse 3.5. Clicking has no effect but keyboard shortcuts still work.

Create a script to start eclipse with the following export…

#!/bin/sh
export GDK_NATIVE_WINDOWS=1
/opt/eclipse-3.5/eclipse

… and remember to change the path to where your eclipse is located.

Check http://www.norio.be/blog/2009/10/problems-eclipse-buttons-ubuntu-910 for a little more background on the problem.