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Category: tech

April 13, 2010

Use ALT-TAB for VNC machine on Linux

by viggy — Categories: linux, tech — Tags: , , , — Leave a comment

This is for those who work usually on systems through VNC, I am one among them. It was very cumbersome for me to select tabs in the VNC system using mouse and not able to use ALT-TAB functionality. Hence when I searched in Google for any solution, I found a very simple soultion.

Just change the ALT-TAB key binding in your linux machine to something comfortable for you. After you have done this, whenever you select ALT-TAB, the system passes that key-binding to the VNC window.

The solution is just that simple. :). Enjoy.

April 7, 2010

How to enable Wireless on CentOS?

by viggy — Categories: tech — Tags: , , , , — 1 Comment

Well since CentOS, in the name of stability never has any latest package installed, it is very difficult to do small things in it which is a matter of few clicks in some other distributions like Fedora or Ubuntu.

However since I had CentOS installed on my laptop, I had to find a way to get my wireless up. So I started searching different ways to do it. First I had to get the system to detect my wireless. For this I followed the wiki given in CentOS, http://wiki.centos.org/HowTos/Laptops/Wireless#head-d0f09f4e13e1089355527862718bbf7548a5a64a

After this I installed latest wireless-tools package which I downloaded from here, http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html

Then I started my wireless using the following command,
ifconfig wlan0 up

After this I tried to find the available wireless connections which I could connect to. This can be obtained by the following command.
iwlist scan

After I found the wireless connection which I used to connect usually, I checked its features. However in CentOS did not give any option for me to enter the configuration in its wireless configuration.

Hence after digging in internet for quite some time, I found out that I need to install wpa-supplicant package . So I downloaded the package and installed it as given in its install file.

After that I needed to put the wireless configuration in the wpa-supplicant.conf file. Luckily I had saved the configuration details that I used in Ubuntu. This I used along with trial and error method to get the right configuration.

You can get the explanation for each variable using “man wpa-supplicant.conf”. Following is the content of my wpa-supplicant.conf file.
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel

network={
ssid=”ABCDEF”
key_mgmt=WPA-EAP
eap=PEAP
identity=”abc@xyz.com”
password=”password”
phase2=”MSCHAPV2″
}

Once wpa-supplicant.conf is configured, start wpa-supplicant connection using the following command:
wpa_supplicant -iwlan0 -c/etc/wpa_supplicant/wpa_supplicant.conf -d

Voila. Now you have your wireless connection detected and working properly. Enjoy.

March 24, 2010

Custom icons to your script

by viggy — Categories: tech — Tags: , , , — Leave a comment

I have to use VNC many times for my work. Everytime to invoke vncviewer, I had to press -F2 and then type “vncviewer”. I didnt want to do this and hence I thought I will write a simple shell script which I can use to run whenever I needed vncviewer. Hence I wrote following two lines in a shell script.

#!/bin/bash
vncviewer

This I saved on my desktop and used to double click it whenever I needed to run it. However even this used to ask me if I wanted to run it or display it. Also the script had a default icon which I didnt want and wanted it to have the icon of vnc. Also I didnt like it to occupy my desktop area and wanted to keep it on my panel. Hence i searched on google for answers. i found the following mail which gave me a clear idea of how to do it.

http://linux.derkeiler.com/Mailing-Lists/KDE/2009-04/msg00131.html

You can create your own icons by creating a textfile and giving it a .desktop
extension. That’s all an icon is. Go to /usr/share/applications and have a look.
Anyone of those files can be dragged into you ~/Desktop folder if you use that for
desktop icons or else directly onto your desktop.

The format of the .desktop file is fairly simple to follow I have made them for
url as well as script icons and keep them in /usr/local/share/applications. Once
you have created the file the “icon” can be used like any other icon, e.g. adding
to Quicklaunch. Use anything for an icon. Here is what one of mine looks like.

[root@localhost ~]# cat /usr/local/share/vncviewer.desktop
[Desktop Entry]
Name=Vncviewer
Comment = runs vncviewer script
Exec=/usr/local/bin/vncviewer.sh
Icon=/usr/share/icons/vncviewer.jpeg
Terminal=0
Type=Application
Categories=Application;Internet;

Hence now I could drag this icon on my panel and launch vncviewer in just one click.
:)

March 23, 2010

Fatal: Module fuse not found

by viggy — Categories: linux, tech — Tags: , , — Leave a comment

This was the error that I was getting when I tried to mount my NTFS partition in CentOS5.3 final. I tried to search for a solution for one full day but I couldnt find a solution. Finally I got a forum where it was suggested that this is basically a mismatch of kernel-headers and kernel modules. So I tried to find the kernel-modules which matched my kernel-headers version. However even after I tried to install the correct version of kernel-modules, I still faced the same issue. Hence I finally gave up and decided to upgrade my kernel to the latest stable version.

So when I updated my kernel to 2.6.18-164.15.1.el5, and I rebooted, I could easily mount the NTFS partion.

March 1, 2010

Why I did not subscribe to Google Adsense?

by viggy — Categories: tech — Tags: , , — Leave a comment

Around 4-5 months ago I had an idea of starting a portal dedicated only to all the errors faced by GNU/Linux users. I had thought that if there is one portal where every user can post and search for the error message that he got while using GNU/Linux, sooner or later these portal will become a good database of all the commonly found errors faced while using GNU/Linux. And then I had thought of using Adsense to generate money to maintain portal and if possible make some profit myself.

However the main question that I asked to myself before using Adsense was “Can I restrict the Ads that are displayed through Adsense?” Because I didnt want the portal to end up promote any proprietary softwares through google adsense? I knew about Adbard then, but I did not believe using Adbard would help me earn as much as Adsense. Anyways I thought that google must have some way through which I can restrict some ads or allow only a category of ads. So when I asked this question in the Google Adsense help forum they told me that unfortunately they did not have any category for proprietary softwares. Anyways I figured out Adbard was the only solution for my problem.

I remembered the situation after all these days when I opened a blog by a core developer of Ubuntu Server and I see MIcrosoft Online Services ad, sad isnt it?
Why Open source enthusiasts should not use Google Adsense?

January 13, 2010

split and join huge files

by viggy — Categories: linux, Misc, tech — Tags: , , , , , , — Leave a comment

I recently has asked my friend to download edubuntu9.10 iso . It was a 3.4 gb iso. After he finished downloading when i had to transfer it to my system, we faced a small problem. His LAN card was not working and we had only 1gb pen drive. So the only option we had was to split the iso into files of size 1gb and then transfer them using pen drive.

command to split a huge file into smaller file.

split -b 1G

is the prefix of the smaller files that will be created.

After I split the files, i transfered each file in to my system and then joined the files using a very simple “cat” command.

Join the files splitted by the above commad.

$cat aa bb cc dd>huge-filename

The above command will join all the files and create the file huge-filename.

I need to test whether the order of the smaller files matters in the cat command. Logic says that it should matter. lemme check it out.

Confirmed it. The order of the smaller files is very importent to get back the original file.

January 3, 2010

real player sound problem solved

by viggy — Categories: linux, tech, ubuntu — Tags: , , , , — Leave a comment

Thanks to this post, I was able to solve the real player sound problem in my machine.

1. Enable Alsa soft-mixing as described in post http://ubuntuforums.org/showthread.p…multiple+sound
(also setup esd and multimedia system settings as described in that post)

2. Install realplayer as described in http://ubuntuguide.org/#realplayer

3. Install alsa-oss

4. Open the launcher script realplay located in Realplayer’s install directory (/opt/RealPlayer if you followed previous instructions)

5. Find lines
Code:

if [ -n “$LD_PRELOAD” ]; then
echo “Warning: LD_PRELOAD=”$LD_PRELOAD””
fi

6. …and after add this code:
Code:

LD_PRELOAD=”$LDPRELOAD:/usr/lib/libaoss.so”
export LD_PRELOAD

7. Now you get RealPlayer working with Alsa mixing (and so combinations of Realplay, Xine, Mplayer, Frozen Bubble,…sounds work at the same time )
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December 11, 2009

rm -rf *

by viggy — Categories: debian, linux, tech — Tags: , , — Leave a comment

I just got an idea of trying out the command rm -rf * in a virtual system. I had thought of creating a new domU in xen server in the office and then testing in it. However I just tried to switch on my Desktop which had been shut since last week due to some problem with my HDD. Strangely when I started the desktop, the BIOS detected my HDD and it booted into ubuntu. Now this made my expiriment lot more easier because now all I had to do was take a backup of the VM image and then boot using the image in qemu.

After booting up I started a screen and tried the command
rm -rf /
I got an error saying that “/” could not be deleted.

Then I tried the command
cd /; rm -rf *

and then it started deleting all the files in my filesystem. I went to another screen and tried the command “ls”. It told me that “ls” command not found. Then I tried various commands, but none of them worked, except echo and cd. I dont know why these didnt get deleted.

At last I was left with following file structure:
notice:/# cd
dev/ home/ lib/ proc/ .rnd sys/ var/

When I just press Tab twice, I get the following output:

notice:/#
: } case continue elif export getopts kill popd select then ulimit
! alias cd declare else false hash l printf set time umask
./ bg cdcgi dirs enable fc help let pushd shift times unalias
[ bind cdtmpl disown esac fg history ll pwd shopt trap unset
[[ break command do eval fi if local read source true until
]] builtin compgen done exec for in logout readonly suspend type wait
{ caller complete echo exit function jobs ls return test typeset while

Though this would be a very stupid thing to do in any circumstances, I didnt loose anything as I was just testing it on a VM. However the importent question still remains that is there any way to recover fmo here?

December 9, 2009

pushd and popd commands

by viggy — Categories: linux, tech — Tags: , , , — Leave a comment

Suppose you are presently working some directory and for some reason you need to cd into some other directory for some trivial but urgent work. So how do you remember which directory you were in. This is where pushd and popd commands are used.
Pushd command adds a directory to the top of the directory stack, or rotates the stack, making the new top of the stack the current working directory. With no arguments, exchanges the top two directories and returns 0, unless the directory stack is empty.
sumit@sumit-Desktop:/var/www/cgi-bin$ pushd /usr/share/apps
/usr/share/apps /var/www/cgi-bin
sumit@sumit-Desktop:/usr/share/apps$

and popd command removes entries from the directory stack. With no arguments, removes the top directory from the stack, and performs a cd to the new top directory.
sumit@sumit-Desktop:/usr/share/apps$ popd
/var/www/cgi-bin
sumit@sumit-Desktop:/var/www/cgi-bin$

I hope it is useful. Definitely very useful for me.

December 7, 2009

svn commit error

by viggy — Categories: tech — Tags: , , , — Leave a comment

I wanted to commit to a repository but whenever i tried the “svn commit” command. I was getting the following error.
svn: Server sent unexpected return value (500 Internal Server Error) in response to MKACTIVITY request for’ ‘
Well I did not understand what the error was till i checked the svn info.
The error was because I had checked out the code using http protocol and hence I had not been authorized to commit. So what I did was checkout the code again using https protocol.
However my senior told me that the right way is to do “svn switch”.

svn switch NEW_URL