Posts Tagged ‘tech’
Last weekend, CMRIT GLUG along with IBM and FSMK conducted a 2 day workshop, “FOSS for Budding Developers”. This workshop was completely technical in nature and among the many FOSS workshops that I have attended, one of the most useful one for me. The professionalism of IBMers could be seen during the workshop which was also the main reason for the huge success of this workshop.
The workshop covered the following topics,
Day 1
Day 2
I was interested in Linux Kernel Developement and the Linux Test Project sessions. I had taken my laptop to make the best use of the workshop.
I have been using GNU/Linux since last 2 years, but never did I get the courage to compile and build the Linux kernel. Only around 6 months back, I had for the first time with help of Naresh, installed the new linux kernel on my system using apt-get. The main reason for not trying out building my own linux kernel was that I was afraid that I would loose all the data I had in my system. However for the workshop I had decided that I will try it out. So when the Linux Kernel session started, I was very excited.
In the pre-lunch session, we were introduced to various tools that any Hacker would require while trying to read the source code or build from source code. We were introduced to gcc, gdb, make, makefiles, strace,ltrace and cscope tools. Though I knew little about gcc and gdb, I realized the importance of the other tools. I particularly was marveled by “cscope” and “strace”. Optimized use of cscope will surely decrease the time taken to go through the source code for any developer. I remember it had taken me around 2 months just to go through the Evolution source code. If I had used cscope then, it would hardly take me 2-3 days for the same. We were given a very brief introduction to cscope during the session, but I will learn more about it myself and write about it in the near future.
The pre-lunch session thus prepared the ground for us to venture in to building the linux kernel.
Post-lunch we started with Building the Linux Kernel 2.6.33.2 version. I was amazed by the simplicity involved in building the kernel. It is just a 7 step procedure, if you are building the kernel for your own desktop or laptop.
It took around half an hour to execute. After this I just need to update my grub if it has not been done by the above steps already. Just confirm it by having a look at /boot/grub/grub.cfg. If the new kernel lines are added then you are ready to Reboot and use the new kernel which was just built.
Thats all.
After booting into the new kernel, we started writing simple codes for new kernel modules and drivers. Again the simplicity of writing a new module or driver and loading it amazed me. However a lot more has to be explored and I will definitely try them in future.
On day 2, I attended the Linux Testing Project workshop. It was again wonderfully planned by the IBM team. We were first given a brief introduction to the history and importance of the Linux Testing Project with the team making it very clear that the testing cycle is as important as the development cycle. After this we had a hands on session.
In the hands on session, we started with building the Linux Testing Project in our systems. Than the IBM team had come with some tasks for us. We were asked to run a test case which was written such that it fails intentionally. This was done so that we could study the test case and come up with a solution as to why that particular test case was failing. I had teamed up with Saket and together we were very close to finding the solution. It was quite fun and really a good Hacker workshop.
There were many interesting points that we noted while trying the Linux Testing Project. One among them was, I was using Linux Kernel 2.6.31.x where as Saket was using Linux Kernel 2.6.33.2. So when we executed the Containers Testcases on our systems we found that some test passed successfully in my system but failed in Saket’s system. This clearly showed us that Linux Kernel 2.6.33.2 had some bugs. We did not dig into the matter due to lack of time. However I need to check it soon.
I have skipped lot of technical details here as I will give the technical details later when I try it again myself.
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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.
How to enable Wireless on CentOS?
Posted on: April 7, 2010
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.
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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?
split and join huge files
Posted on: January 13, 2010
- In: linux | Misc | tech
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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.
$cat aa bb cc dd>huge-filename
The above command will join all the files and create the file huge-filename.
I need to test whether the order of the smaller files matters in the cat command. Logic says that it should matter. lemme check it out.
Confirmed it. The order of the smaller files is very importent to get back the original file.
real player sound problem solved
Posted on: January 3, 2010
- In: linux | tech | ubuntu
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Thanks to this post, I was able to solve the real player sound problem in my machine.
1. Enable Alsa soft-mixing as described in post http://ubuntuforums.org/showthread.p…multiple+sound
(also setup esd and multimedia system settings as described in that post)
2. Install realplayer as described in http://ubuntuguide.org/#realplayer
3. Install alsa-oss
4. Open the launcher script realplay located in Realplayer’s install directory (/opt/RealPlayer if you followed previous instructions)
5. Find lines
Code:
if [ -n “$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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rm -rf *
Posted on: December 11, 2009
- In: debian | linux | tech
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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?
pushd and popd commands
Posted on: December 9, 2009
- In: linux | tech
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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.
svn commit error
Posted on: December 7, 2009
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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
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