• Tutorial: Remove a PPA in Ubuntu (and restore original packages)

    Let’s face it, we love to test new applications, improve our system and see new things…

    However in some occasion, after we’ve updated our system by adding a PPA in our Ubuntu (sudo add-apt-repository ppa:NAME_OF_THE_PPA) you discover that you are not interested in what you’ve just installed, it doesn’t work as expected or simply you want to remove it…

    When you install a PPA you don’t only add the software you want to install as normally you’ll have all the required dependencies (that in some cases are in a newer version than the ones installed in your system). Therefore, when uninstalling a software that you’ve got from a PPA, you should care of removing all the extra packages and re-instate the original versions of the ones you had before.

    Luckily, you don’t have to do this manually… Thank you ppa-purge!!!!

    You can install ppa-purge by simply run in console:

    sudo apt-get install ppa-purge

    By running it you will be able to see its syntax:

    sudo ppa-purge [options] <ppa:ppaowner>[/ppaname]

    So, if for example you’ve previously installed a PPA called ppa:username/coolsoftware:

    sudo ppa-purge ppa:username/coolsoftware

  • Tutorial: Remove/Delete Keys in Firefox about:config

    The other day I was doing some routine maintenance on my system and while navigating inside my Firefox configuration (yes, the about:config command that you put in the URL field) I’ve found quite a few old keys related to addins that I’ve removed quite long ago.

     In order to remove them I’ve seen that there are two simple ways:
     
    The first method is good if you have to remove a small number of entries: right click with the mouse on the entry you want to delete and select Reset. Now you will notice that after restarting Firefox, that entry value will be reset to its default value if it’s one of the Firefox internal ones, otherwise it will be deleted.

    The second method is good if you have to remove a big number of entries:

    1. Close Firefox
    2. Open the file “prefs.js” that is located under your Firefox profile at ~/.mozilla/firefox/xxxxxxxxx.default/ (where the x’s stand for a randomly generated code that will change for each profile) using your favourite editor.
    4. Delete all the entries you want
    5. Save the file and restart Firefox

  • Tutorial: using Raspbmc on different networks

    If you are using your Raspberry PI as media centre using RaspBMC, you are probably good to go in a few minutes, being RaspBMC a mature project that is now easy to install, configure and use.

    RaspBMC Logo

    However by default and for security reasons, Raspbmc’s “iptables restricts network to LAN only by default“. This means that if you have more than one router in your environment, your RaspBMC will be able to reach the internet and any device on its own LAN, but will not be seen by other devices in another lan.

    If you try to ping it, it will not answer, unless you are on a device that is on the same lan.

    Let’s see the following image to see a bit more in details a possible scenario:

    Network_Topology

    Let’s say that you have already put in place a static route to make sure that the computer on the first network segment can reach the second one and viceversa.

    In order to be able to reach the RaspBMC machine, you will need to configure IPTables:

    sudo iptables -I INPUT -s 192.168.0.0/24 -j ACCEPT

    Then you will need to make this change permanent even after a reboot:

    sudo apt-get install iptables-persistent

    – Open the file /etc/rc.local:

    sudo vi /etc/rc.local

    – Add this line :

    sudo /etc/init.d/iptables-persistent start

     

    Done! Now your RaspBMC will be reachable from any other machine in the specified network segment (192.168.0.0/24)…