www.giannistsakiris.com

If you have just upgraded to Gutsy Gibbon you may noticed that USB support is missing from your VirtualBox. To fix this problem edit the file /etc/init.d/mountdevsubfs.sh:

$ sudo gedit /etc/init.d/mountdevsubfs.sh
[sudo] password for giannis: *****

Find the section with title "Magic to make /proc/bus/usb work". It should look like this:

#
# Magic to make /proc/bus/usb work
#
#mkdir -p /dev/bus/usb/.usbfs
#domount usbfs "" /dev/bus/usb/.usbfs -obusmode=0700,devmode=0600,listmode=0644
#ln -s .usbfs/devices /dev/bus/usb/devices
#mount --rbind /dev/bus/usb /proc/bus/usb

Uncomment the last four lines and make it look like this:

#
# Magic to make /proc/bus/usb work
#
mkdir -p /dev/bus/usb/.usbfs
domount usbfs "" /dev/bus/usb/.usbfs -obusmode=0700,devmode=0600,listmode=0644
ln -s .usbfs/devices /dev/bus/usb/devices
mount --rbind /dev/bus/usb /proc/bus/usb

Save changes and restart your computer. Run VirtualBox again. Now you should be able to see the USB controller options.

See also: Not permitted to open the USB device, check usbfs options.

When your program is not running, go to the menu and select Project → Properites... Go to the Debug tab and locate the Start Options section. You should be able to see a textbox labeled Command line arguments where you can enter your desired command line arguments:

Use spaces to separate command line arguments and make sure that you enclose in double-quotes (") any argument that contains spaces. Save the properties (you can do Save All) and start debugging.

You can take advantage of a neat feature of VirtualBox, Snapshots, to execute Key Generators or any other software of potential risk under Windows XP. Snapshots allow you to save the status of your virtual machine as well as the virtual disk in use. You only have to take a snapshot before running the possibly-malicious software in your virtual machine, and then revert to the saved state when the job is done.

In detail:

• With your virtual machine running go to Machine → Take Snapshot...


• Enter a name for your snapshot (e.g. before running keygen) and press Ok.


• Proceed with the execution of the key generator.


• Write down the generated key. If you want to save the generated key in a text file, make sure that the file is on the host computer, or else it will be lost in the next steps! You can always use a piece of paper, too.


• Power off the virtual machine.


• Go to VirtualBox's main window and go to the Snapshots tab of your virtual machine.


• Right-click on current state and choose Revert.


• Discard the snapshot you previously created.


• Start the virtual machine.

The virtual machine is now in the same state as it was before the execution of the key generator.

I have seen this happening in my Ubuntu 7.04 host running Windows XP Professional on VirtualBox. A bug in VirtualBox causes the host operating system unable to copy anything in the clipboard, when certain applications are running on the guest system (some of them: Remote Desktop Connection, Computer Management, Enterprise Manager).

VirtualBox 1.5.2 fixed this bug. Do the following:

• Download and install VirtualBox 1.5.2 or later


• Boot your guest Windows XP


• Go to Devices → Install Guest Additions...


• Reboot Windows

The problem should exist no more.

No doubt that TortoiseSVN is a killer app. Once you’ve tasted it you are not willing to compromise with anything less.

When I needed a graphical subversion client for GNU/Linux, I did my little search and took some shots on some of the clients I found, but the results were very disappointing as I couldn’t find anything that could mimic TortoiseSVN even by the tiniest bit.

Thankfully, at least there was one client that offers the closest to what I wanted, and it comes from the realm of KDE: kdesvn. It can preview a versioned directory, that means that you can view at a glance all the files that require your attention. It can also open a repository and let you browse its structure (similar, to TortoiseSVN’s repo-browser). In combination with kompare, a graphical front-end for diff, it can nicely display changes in files.

To install kdesvn and kompare in your Ubuntu system run:

sudo apt-get install subversion kdesvn kompare

For convenience I use two custom nautilus-scripts, one for previewing and one for repository browsing:

kdesvn-preview:
#!/bin/sh
kdesvn $1

kdesvn-repo-browser:
#!/bin/sh
kdesvn `svn info $1 | head -n 2 | tail -n +2 | awk ‘{print substr($0,6)}’`

kdesvn-preview will open the selected directory for preview in kdesvn. kdesvn-repo-browser will open the directory of the repository that corresponds to the selected directory (or the current directory if you have not selected anything).

See also: custom context menus with nautilus scripts

If you are getting this error when trying to mount a USB device from Virtualbox, maybe you should try this:

Edit as root the file /etc/udev/rules.d/40-permissions.rules:

sudo gedit /etc/udev/rules.d/40-permissions.rules

Look for the "USB devices" section:

# USB devices (usbfs replacement)
SUBSYSTEM=="usb_device", MODE="0664"

Change mode from 0664 to 0666:

# USB devices (usbfs replacement)
SUBSYSTEM=="usb_device", MODE="0666"

Now restart your computer and try to mount the device again.

Nautilus Scripts allow GNOME users to easily add custom context menu items that invoke specific commands or scripts.

To add a new menu item you have to create a shell script inside your ~/.gnome2/nautilus-scripts directory and make it executable. To invoke the script from the menu right click on Nautilus and go to Scripts. Your shell script should be there. When executed, the script inherits the current working directory from Nautilus.

For example, let's say that we want to add a menu item that will open a new terminal in the current folder.

We go to the folder where all Nautilus Scripts reside:

cd ~/.gnome2/nautilus-scripts

We create our shell script, let's call it open-terminal.sh:

gedit open-terminal.sh

We add the following lines in the file:

#!/bin/sh
gnome-terminal

Save the file and make it executable:

chmod +x open-terminal.sh

Now if you right click on nautilus and go to Scripts you should be able to see your new script:

If you do not see it, make sure that you did the whole procedure correctly. If it still does not show up try to press F5 (reload) or restart Nautilus.

Usually you will want to add a custom script that will perform a specific action on the selected file or files. For local directories, Nautilus will call your shell script passing the selected file or files as command line arguments to the script.

To demonstrate this we will now create another script that will open the selected file for edit in the vi editor (which will run inside gnome-terminal). Go to ~/.gnome2/nautilus-scripts again and create another shell script by the name open-with-vi.sh:

cd ~/.gnome2/nautilus-scripts
gedit open-with-vi.sh

Add the following commands:

#!/bin/sh
gnome-terminal -x vi $1

Save the file and make it executable:

chmod +x open-with-vi.sh

Then go to Nautilus and select a text file. Right click on it, go to Scripts and choose open-with-vi.sh:

You should see a gnome terminal running vi with your file open for editing:

When the script is executed $1 is replaced by the selected file's name. If you want to handle multiple files you will have to traverse all the command line arguments passed to the script, $1, $2, $3, and so on.

Finally, it would be worth to mention that you can organize your Nautilus Scripts in subdirectories inside ~/.gnome2/nautilus-scripts. The subdirectories will appear in the context menu as sub-menu items.

WordPress provides an RSS feed link for every single post you publish in your blog. It is highly unlikely that someone would want her RSS feeds to show up on Google's results.

To prevent Google from indexing your WordPress RSS feeds you will have to create/modify the robots.txt file in your website's root directory. What you will put in your robots.txt file depends on the permalink type you are using.

If you use "pretty" permalinks (like the ones in this website) you will have to add the following:

User-Agent: *
Disallow: */feed/

However, if you prefer the "ugly" permalinks that WordPress defaults to, you will need to add something like this:

User-Agent: *
Disallow: *feed=rss2*

If you are using subversion on your eclipse project's source folders, then you may have noticed .svn folders appearing inside your project's bin folder, even though bin is non-versioned. That happens because eclipse is unaware of the specialness of the .svn folders, and treats them like ordinary resources (thus, simply copying them to bin). This is kind of annoying because the bin folder always seems to be in the modified state, even though it should not be versioned at all.

However, the solution to this problem is fairly simple: Just go to your project → Build Path → Configure Build Path... Select the Source tab and expand all you specified source folders. For each source folder, highlight Excluded: and press the Edit button. Go to the Exclusion patterns and click the Add button. Enter **/.svn/ and click Ok, Finish, Ok. Now the .svn folders will not show up again in your project's bin folder.

Okay, so you installed all required packages to get Sun's JRE and/or JDK in your Ubuntu box, but when you try to run a java program you don't get Sun's jvm.

To see what jvm is your current default, run this command:

~$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 34 2007-10-06 07:40
/etc/alternatives/java → /usr/lib/jvm/java-gcj/jre/bin/java

In this example we see that we are currently using gcj.

To change the default jvm, run this command:

$ sudo update-alternatives --config java

You will be presented a menu with all the available jvms, and you will be prompted to choose your new default:

$ sudo update-alternatives --config java
Password: *******

There are 3 alternatives which provide `java'.

Selection Alternative
--------------------------------------------------------------------------------------------
1 /usr/lib/jvm/java-6-sun/jre/bin/java
2 /usr/bin/gij-wrapper-4.1
*+ 3 /usr/lib/jvm/java-gcj/jre/bin/java

Press enter to keep the default[*], or type selection number: 1
Using `/usr/lib/jvm/java-6-sun/jre/bin/java' to provide `java'.

To check if the new default is set correctly run the previous command again:

$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 36 2007-10-07 12:21
/etc/alternatives/java → /usr/lib/jvm/java-6-sun/jre/bin/java