Kubuntu: Replace Network Manager With Wicd and Vice Versa

WicdEarlier today, on my Kubuntu machine, I needed to replace the Network Manager, which is installed by default, with Wicd. Later I found out that Wicd has issues on its own, so I decided to switch back to the Network Manager after I initially uninstalled it. The whole switching back and forth process was a bit tricky considering I didn’t know how to remove and then install back the Network Manager, so I decided to write myself a reminder post. It’s trivial. Hopefully it will help others as well.

Replacing the Network Manager with Wicd

First, install Wicd (it’s important that you install Wicd first, because if you don’t, the next step will effectively disable your internet connection):

sudo apt-get install wicd

and now remove the Network Manager:

sudo apt-get --purge autoremove network-manager

Logout and back in and you should be set. Your Wicd GUI client should be visible in the tray icon area.

Replacing Wicd with the Network Manager

First, install the Network Manager:

sudo apt-get install network-manager

You’ll also need to install back the plasma network manager tray icon tool. Otherwise, your network will be enabled, but you won’t have a GUI tool to select from WIFI connections.

sudo apt-get install plasma-nm

Now you can uninstall Wicd:

sudo apt-get --purge autoremove wicd

Okay, you should be set. Log out and back in and your plasma network manager tool should be available in the tray area for you to manage your wireless connections.

Linux Matlab Installation Error: Caused by: java.lang. UnsatisfiedLinkError

Matlab

The other day I was installing Matlab 2011b on my Linux machine and when I ran the ./install command in terminal, I got the following error message:

Error: Caused by: java.lang.UnsatisfiedLinkError: /home/petr/matlabinstallation/bin/glnxa64/libinstutil.so: /home/petr/matlabinstallation/bin/glnxa64/libstdc

After some googling, I found the solution.

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ssh-agent forwarding to sudo (root user)

terminal

I use ssh-agent to store my ssh key so that I don’t have to enter the key passphrase every time I access one of my servers over ssh. When I run commands using my regular user (non-root), ssh-agent works as expected, stores the key and issuing commands accessing the server(s) doesn’t request the passphrase. However, when I run commands as a root user via sudo, the key forwarding is lost because itsĀ  mechanism relies on the SSH_AUTH_SOCKĀ  environment variable. However, environment variables are removed when the user is switched to root via sudo. How do we prevent the SSH_AUTH_SOCK variable from being removed when issuing sudo, thereby passing on key forwarding to the root user?

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A solution to the /python2.7/site-packages/_mysql.so: undefined symbol: mysql_kill error

mysqlI use Django with MySQL and I this error bothers me almost every time I start a new project with a fresh new installation of Django and relevant Python packages. I use virtualenv to isolate my Python environment for each project. The problem that’s causing this error is that the Python MySQL libraries that are installed via aptitude (I am on Ubuntu) are too old and need to be recompiled.

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Installing MongoDB 2.6 and Setting up Root User Login

mongoI recently started using MongoDB and I was struggling setting up the equivalent of a root user and other users in traditional SQL databases. MongoDB comes with authentication turned off out of the box, so in order to use the password challenge authentication, we have to create the root user followed by enabling the authentication. In this tutorial, we will cover that as well as installing MongoDB on Ubuntu.

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Parrot ARDrone 2.0 Video Streaming through OpenCV in Linux

Parrot ARDrone 2.0

Recently, I got the Parrot ARDrone 2.0. Enjoying taking control of electronics and software, I wanted to write my own code that will stream the video from the quadcopter to my computer and give me the ability to process the individual video frames with OpenCV. There are lots of examples how to do this for ARDrone 1.x, but virtually nothing for ARDrone 2.0, which completely changed the way it’s streaming the video. After many hours of research and putting different pieces of code together, I got it to work on ARDrone 2.0. In this post, I will show you how to do it.

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Copy Your Subversion Repository Using URLs With svnsync

Subversion svnsync copy repositoriesI was recently in a situation when I needed to move my Subversion repository from one server to another. One option was to use “svnadmin dump”, but that requires you to have access to the file system on the server where the repository sits as well as knowing what directory the repository is in. It turns out that a much sleeker way to do this is using the svnsync tool because all you need to know for that solution are the URLs of the source and target repositories. Here’s how:

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