Santanu's Linux LogBook

RIP Dennis Ritchie

2011-10-13T04:05:00.000-07:00

Today is indeed a very sad day for me. We have lost a great mind. Dennis Ritchie was one of my heroes. RIP Dennis Ritchie.

Skype in Linux

2009-12-19T14:18:00.000-08:00

Recently I have started using Skype in Linux for video calls (calling home). My webcam (Logitech QuickCam Connect) works well in Linux but not directly under Skype (2.1.0.47). I am on Ubuntu 9.10. After some net surfing, I found two solutions that worked:

Solution#1:
Install gstfakevideo.
If webcam is at /dev/video0, then move it to, say /dev/video1 (gstfakevideo will use /dev/video0 for itself by default. This also means that in Skype Video settings, /dev/video0 is to be selected).
Start Skype as follows:

gstfakevideo v4l2src device=/dev/video1

Solution#2:
Install libv4l (in Ubuntu it is libv4l-0).
Start Skype as follows:

LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so /usr/bin/skype

(change the above path names depending on where the libv4l and skype are installed in your system)

Now that I got video working under Skype, I faced another problem. The video was too dark, and the current Skype version for Linux does not provide any option to change the brightness, contrast, etc. Again, some net surfing, and the solution that works for me turns out to be xawtv.

xawtv includes along with it a tool called v4lctl, which allows one to control brightness, contrast, etc. of the video stream from v4l devices. For me, a simple

v4lctl bright 250

from the terminal during a Skype video call solved the brightness problem. For other options that can be changed via v4lctl, do a

v4lctl list.

I can't exactly remember the URLs from where I collected those solutions, but I do remember that all of that info was from the Skype forums.

Narrowing down to a region in Emacs

2009-03-22T14:10:00.000-07:00

Emacs is awesome! What a piece of software! Recently, I discovered a very useful feature in Emacs.

Let's say, you are writing some documentation in text-mode. Inside it, you need to write a piece of C code with proper indentation. You can switch to c-mode, but then the rest of your text starts looking weird with colors and all, and this is very distracting (to me at least). But Emacs, as usual, has a solution to this problem.

Select a few blank lines (where you want to insert your code) within the text, and give the command M-x narrow-to-region (the keyboard shortcut for this is C-x n n). You will find yourself in a buffer with only the region you selected. Then you can enter c-mode and write the code. When done, you can go back to your original full view by using the command M-x widen (or C-x n w) and switch back to whatever mode you were in (text-mode in this case).

I find this pretty useful.

Using "Abbreviated Skeletons" in Emacs

2009-03-22T13:50:00.000-07:00

In Emacs, you can use code templates (using 'skeleton's in emacs) as abbreviations to speed up your coding. Here is an example:

Suppose I want to create a code-template for the for loop in c-mode in Emacs. To create the template, I can put the following function in my .emacs file:


(define-skeleton c-for
  "Inserts a C for loop template."
  nil
  > "for (;;){" \n
  > _ \n
  "}" > \n
  )

(see the Autotype section of the emacs info)

After that, I can edit the abbreviation table by using the command M-x edit-abbrevs (i.e., Press Alt+x, and then give the command edit-abbrevs and press enter).

Then, under the heading (c-mode-abbrev-table), leaving a blank line, I can enter the following line:


"forst"   0     ""      c-for

Then, I can save the changes by pressing C-c C-c (i.e., press Control+c twice). That's it.

Now, whenever I am writing a C program, if I need to use the template, I will just type "forst" (without the quotes), and if the abbrev-mode is turned on, then as soon as I enter a space, my template for the for statement gets entered with the cursor inside the for loop as follows:


for (;;){
  _
}

(If the abbrev-mode is turned off, "forst" can still be expanded to the template by pressing "C-x a e", which basically stands for "abbreviation expand".

Oh, of course I need to save my abbreviations using M-x write-abbrevs-file if I want to use them in future emacs sessions. But that is obvious... although I have forgotten that on many occassions :-)

How I connected to Internet from Linux via Airtel GPRS

2009-03-11T08:39:00.000-07:00

First of all, I needed to activate Airtel's MO (Mobile Office) GPRS service. At the moment, they provide a form of this service by which I will be charged @ 30p/50KB (at least that's what I understood from their website). So, here is what I did:

Activating the MO service

Dialed *567*1# to activate (*567*2# to deactivate) the service on my prepaid Airtel connection.

Configuring the mobile

To configure the mobile for the MO service, I needed to set the active GPRS access point to airtelgprs.com. I have a Nokia 3220. There I had to set airtelgprs.com under Settings -> Connectivity -> GPRS -> GPRS Modem Settings -> Edit Active Access Point -> GPRS Access Point. Also, I set the Alias for Access Point, and Active Access Point to airtelgprs.com. That was all I had to do on the mobile side.

Connecting the Mobile to my Linux box

I connected the mobile (Nokia 3220) using the Nokia CA-42 cable to an USB port on my 4 yr old Compaq Presario 2203AL Laptop running Fedora 10. I made sure that the kernel had recognized my mobile as an USB modem. I checked that using the command dmesg. Among the several lines of output, the following lines appeared:


usb 2-2: new full speed USB device using uhci_hcd and address 2
usb 2-2: configuration #1 chosen from 1 choice
usb 2-2: New USB device found, idVendor=0421, idProduct=0802
usb 2-2: New USB device strings: Mfr=0, Product=0, SerialNumber=0
cdc_acm: This device cannot do calls on its own. It is no modem.
cdc_acm 2-2:1.0: ttyACM0: USB ACM device
usbcore: registered new interface driver cdc_acm
cdc_acm: v0.26:USB Abstract Control Model driver for USB modems and ISDN adapters

Thus, my mobile was detected as an USB modem with device name ttyACM0 under the /dev directory.

Linux side configuration

First of all, I made sure that I had turned off my wi-fi connectivity on this laptop. Also, I don't use ethernet on this laptop. So, basically, I got totally offline. All I had to do now was to use wvdial program to connect to the internet via the mobile. For that I needed to create the file wvdial.conf in /etc/ directory, and put the following lines in it:


[Dialer Defaults]
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = USB Modem
Phone = *99***1#
Stupid Mode = 1
ISDN = 0
Username = "none"
Init1 = ATZ
Password = "none"
Modem = /dev/ttyACM0
Baud = 230400

Once that was done, I ran the command wvdial from a terminal with root privileges. (Of course, later I intend to write a suitable udev rules file so that the permissions of the ttyACM0 device will be set such that I will be able to run wvdial as a normal user.) Connectivity was established, ppp was started, and along with several lines of output from wvdial, I found the following lines of information:


--> local  IP address 117.99.41.9
--> remote IP address 10.6.6.6
--> primary   DNS address 202.56.230.5
--> secondary DNS address 202.56.250.6

I checked using ifconfig that ppp was up. Also, the command route -n showed that my default gateway was 10.6.6.6 as expected from the above output. I then manually set the nameservers in the file /etc/resolv.conf.

That's all I had to do. I could now successfully ping any website, and surf the net, although very slowly... but who cares, it was fun :-)

To stop the connection, I just had to stop wvdial by pressing Control-C.

Making Xmonad to show up in gdm session list

2009-03-08T03:49:00.000-07:00

I am now for some reason having to use Fedora 10 on my home laptop... partly by choice, partly due to circumstances. As I expected, xmonad is not in yum repos (neither Fedora nor RPMFusion)... but thankfully, ghc and haskell libraries are. Anyways, I found an easy way to install haskell packages once ghc and friends are installed (more about that in a later post... probably). Well, installed xmonad, xmobar, etc. along with gmrun (this was in yum repos).

But now that I have xmonad installed, I needed xmonad to show up in gdm session list so that I could choose it over gnome. I had done this quite a while ago, before I started using debian based distros... so I had to re-learn the process (Xmonad FAQ page made the process trivial). Now that I know how it works, I thought I should blog about it so that I can look it up here again in case I forget again.

Well, after so much blah blah, the process is pretty straightforward. As with most Unixy ways of doing things, you just have to add a .desktop file, say, xmonad.desktop to "/usr/share/xsessions/".
The contents of this file is also quite straightforward:


[Desktop Entry]
Encoding=UTF-8
Name=xmonad
Comment=This session starts xmonad
Exec=/home/sc/.cabal/bin/xmonad
Type=Application

(OK, so you (assuming somebody other than me reads this) probably figured out by now that I used cabal to install xmonad... well, that saves me a blog post I guess :-)

xmonad should show up along with others in your gdm session list.

Creating a Calendar in Linux

2009-02-16T01:03:00.000-08:00

Today I found a great program called "pcal". It can create good looking postscript calendars. Most importantly, it can mark holidays in the postscript output if a 'date file' (normally named .calendar) is provided to it.

I created a holiday list in my .calendar file as follows (the * after the dates indicate a holiday):


8/1/09*         "Muharram"
23/1/09*        "Netaji's Birthday"
26/1/09*        "Republic Day"
31/1/09*        "Saraswati Puja"
10/3/09*        "Fateh-Duaz-Duham"
....

and then used pcal as follows to generate a nice single a4 page calendar for 2009:


pcal -P a4 -o cal2009.ps -E -f .calendar -g holiday -w 2009

Here,
'-P a4' generates output for A4 sheet,
'-o cal2009.ps' names the output file,
'-E' lets pcal know that my "date file" has dates in European format,
'-f .calendar' tells pcal the name of my "date file",
'-g holidays' tells pcal to use a particular color (in my case the default grey) for holidays,
'-w' tells pcal to create a whole year calendar (i.e. a full year on a single page).

Setting "SHMConfig" to "true" for synclient to work in recent Linux distros

2009-02-14T05:37:00.000-08:00

Situation:
==========

1. You use a synaptics touchpad on your laptop/netbook.

2. You use a recent Linux distro (like Fedora 10) that comes with a
blank /etc/X11/xorg.conf.

3. You don't like the way your distro has configured your touchpad by
default. For example, you would like to get a middle click by
tapping the upper right corner of the touchpad.

Solution:
=========

To change the synaptics touchpad options at runtime (i.e. while the X
Server is running), you need to use the command line program
"synclient" (or graphical programs like gsynaptics, etc.).

I prefer the command line "synclient" because it allows me to tweak a
lot of things that gsynaptics does not allow me to.

For example, to get a middle click by tapping the upper right corner
of your touchpad, run synclient with the following option:

synclient TapButton2=2 RTCornerButton=2

Read the synclient manual page for more details. Do a 'synclient -l'
to get the current user settings.

In Ubuntu 8.10, synclient is provided by the package
xserver-xorg-input-synaptics.

In Fedora 10, synclient is provided by the package
xorg-x11-drv-synaptics.

But to get synclient working, you need to have the option "SHMConfig"
set as "true" in your options to Xorg. This was earlier done by adding
the line:

Option "SHMConfig" "on"

in your /etc/X11/xorg.conf file in the Synaptics InputDevice section.
Now that this file is being deprecated, you need to find out how you
can provide this option to Xorg. If you are on Fedora 10 like me
(maybe this is also the case in Ubuntu 8.10, Fedora 9, etc.), you can
put this option in a hal configuration file in /etc/hal/fdi/policy/

Using root privileges, create a file named say, synaptics.fdi, in
/etc/hal/fdi/policy/ using your favorite editor, and put the following
there:


<?xml version="1.0" encoding="ISO-8859-1"?>
<deviceinfo version="0.2">
<device>
<match key="info.capabilities" contains="input.touchpad">
<match key="info.product" contains="Synaptics TouchPad">
<merge key="input.x11_options.SHMConfig" type="string">true</merge>
</match>
</match>
</device>
</deviceinfo>

Next, restart by using the command (as root):

/etc/init.d/haldaemon restart

(The above command is for Fedora users. Use hal instead of haldaemon
if you are on Ubuntu)

Next, restart X Server using the command:

killall -HUP Xorg

Once X Server restarts, you should be able to use synclient without
any problems.

For more information regarding Synaptics Touchpad configuration
and configuring other devices under Xorg, see
http://wiki.ubuntu.com/X/Config/Input

Hacked an old driver to work under new linux kernels

2008-12-05T04:52:00.000-08:00

Yesterday, I had to purchase a "PCI to parallel port" multi-I/O card to get the Xilinx Parallel IV cable to work on the Dell machines in our Lab (these PCs did not come with a parallel port, only USBs).

The card was from EnterMultimedia based on WCH352 chip. I am currently on Ubuntu 8.10 with 2.6.27 kernel. But after connecting the card and rebooting, the card was not detected by Linux. Well, actually it did detect it, but as some serial device for which no driver was found, and I could not find any /dev/lp0 or /dev/parport0. So, I looked into the driver CD that came with it, and found a linux driver (I did not expect to find it though)!
Tried to install it, but it turned out to be trying to use lp.o and parport_pc.o modules, both for old 2.4 linux kernels. No wonder the modules were not found in my system (and would not load even if they were present). To make matters worse, the 'installer' (well, hardly an installer... seemed to me more like a program that acted as some kind of wrapper using lp and parport_pc kernel modules for their work) was a compiled binary file without any source code provided on the CD.

So, after some head scratching, I decided to open the binary file using vim, and searched for 'parport_pc.o' and 'lp.o'. Found it, and then replaced them with 'parport_pc.ko' and 'lp.ko' respectively. Tried to run the file again, and it promptly responded with a segmentation fault. I had definitely jumbled up the addresses of different instruction in the binary, which the linker had worked hard to setup.

Then I did two things. First, changed the binary file so that now, 'parport_pc.ko' became 'parprt_pc.ko' and 'lp.ko' became 'l.ko' so that their length became same as their original names in the binary. Second, made a copy of the corresponding modules in my system and renamed them to reflect the new names for the binary file to be able to load them. Then, I ran depmod (I don't think it was required though, but well, did not hurt anyway).

Now I ran the binary file again, and voila, new devices /dev/lp0, /dev/lp1, /dev/parport0 and /dev/parport1 (dunno how lp1 and parport1 appeared though) have now appeared in my system :-)

Compiled Metacity (from svn) to get drop shadows!

2008-04-18T06:05:00.000-07:00

Yesterday I tried compiling metacity downloaded from subversion.

I read an article (from epologetics.org) containing some information on
compiling metacity from subversion. Following it, I first installed the
following packages on my Ubuntu 7.10 (Gutsy) system:
--------
sudo apt-get install gnome-common build-essential autoconf gnome-devel libtool
-------

Then, I tried to run:
-------
./autogen.sh
-------
which gave some errors about something like 'shift 370: can't shift that many'.
Then I tried reading the autogen.sh file and noted somewhere that I required
automake-1.10. My installed version was 1.9. So I installed 1.10 and tried again.

This time it progressed much further, but again bailed out while trying to run
aclocal-1.10. The error said something about '/usr/share/aclocal' being an invalid
option. I tried reading up on the aclocal manual page, and found that, to include
a directory of m4 files for aclocal, you need to use the -I option.
Another reading of autogen.sh showed that it was somehow calling gnome-autogen.sh.
Then I tried reading the relevant portion of gnome-autogen.sh where it was calling
aclocal-1.10. Turns out that it was calling aclocal as 'aclocal-1.10 /usr/share/aclocal'.
I tweaked this file a little so that it was now calling aclocal as
'aclocal-1.10 -I /usr/share/aclocal'. After that I again ran ./autogen.sh.
This time ran to completion... also invoking './configure' somehow, which also seemed
to run fine.

Now I ran 'make' and everything went smoothly. I was able to successfully compile
metacity from subversion on my system. Oh I forgot to mention, I used the enable
compositor option for configuring metacity, and now I get drop shadows in windows
and the gnome panel in metacity... cool :-)

By the way, I have the feeling that I would not have to do all these tweaking stuff
and everything would have gone smoothly if I had used gnome-common from
subversion (as was mentioned in one of the files I read) instead of the version
available from Ubuntu's gnome-common package.

Update: Just now (19th April, Saturday), I tried doing the same thing on a
different computer (this too, an Ubuntu Gutsy, but this one has access to the
internet and is regularly updated). Here, I did not need to put the '-I' option on the
aclocal line in gnome-autogen.sh file (as mentioned in my original post). In fact,
it gives me an error if I do so. But without that, the thing compiles just fine (with
automake 1.10 installed).

2007-12-22T22:59:00.000-08:00

I have been using XMonad as my primary window manager for a few weeks now. No problems whatsoever. But today, I felt like playing with Netbeans a little. That's when I discovered that Java applications don't seem to be able to draw their windows on the screen (except the splash screens) when under XMonad. I have seen that under GNOME/Metacity, the same application works fine. So, I googled for a bit and found this: http://www.haskell.org/pipermail/xmonad/2007-June/001078.html

It seems that the problem appears only with apps using the swing toolkit. But the solution is simply to set an environment variable:
--------------------------------------------
export AWT_TOOLKIT=MToolkit
--------------------------------------------

Thats all that was required to solve the problem.

Manual install of a package and 'pkg-config'

2007-11-09T23:00:00.000-08:00

I tried to install the rtorrent package manually. So I downloaded http://libtorrent.rakshasa.no/downloads/rtorrent-0.7.9.tar.gz. Now, rtorrent depends on libsigc++, libcurl and libtorrent. The required versions of libsigc++ and libcurl were already installed on my system. I decided to manually install (just for fun) libtorrent. So I downloaded http://libtorrent.rakshasa.no/downloads/libtorrent-0.11.9.tar.gz.

Next I did the routine "untar, configure, make, make install' cycle on libtorrent (I used the configure option --prefix=$HOME). No problems. When I tried the same on rtorrent, 'configure' complained that libtorrent was not found.

Well, after some poking around, I found that 'pkg-config' that is used for finding libraries needs the path to a file named "library_name.pc" to be added to the environment variable PKG_CONFIG_PATH for it to able to find the library. In my case, libtorrent.pc was in ~/lib/pkgconfig. So, once I added to PKG_CONFIG_PATH, rtorrent compiled and installed fine.

Skipping compiz blacklist check in Ubuntu Gutsy

2007-11-08T02:16:00.000-08:00

Today, I upgraded one of our Ubuntu boxes at our lab from Feisty to Gutsy. I was expecting to see compiz-fusion in its full glory. But unfortunately, that was not to be.

Although the upgrade went smoothly. But after the upgrade (followed by a reboot), I found compiz was not enabled by default. So, I manually tried to enable compiz (System -> Preferences -> Appearence -> Visual Effects). But it failed with the message "Blacklisted PCIID '8086:29a2' found". Turns out that the Intel i965 Video chipset used by our Dell Dimension has been blacklisted by Compiz in Gutsy. Fortunately, fixing this was easy. A little google search turned up the workround.

Just put the line "SKIP_CHECKS=yes" in ~/.config/compiz/compiz-manager and then tried again. This time it succeeded. (The file 'compiz-manager' and the directory 'compiz' was not there. So I had to create it first).

Now, compiz is working! From what I read somewhere on the web, I might have problems playing videos with compiz enabled on this machine. But I also read that there is probably a compiz-fusion plugin to solve that problem too (didn't try it yet though)

Worked around a keyboard problem in our lab

2007-11-02T05:51:00.000-07:00

Today, I had to work with a broken keyboard where all the Shift+(non-keypad number) keys were broken. So, I could not get !@#$%^&*() characters. To work around this problem, I created a ~/.Xmodmap file containing the following.

-----------------------------------------------------------------------------------
# This maps the keypad number keys so that they generate
# the exclam, at, etc. characters when pressed aong with
# the Shift key. This rectifies a keyboard problem where
# all the Shift+(non-keypad number) keys were dead!

keysym KP_1 = KP_1 exclam
keysym KP_2 = KP_2 at
keysym KP_3 = KP_3 numbersign
keysym KP_4 = KP_4 dollar
keysym KP_5 = KP_5 percent
keysym KP_6 = KP_6 asciicircum
keysym KP_7 = KP_7 ampersand
keysym KP_8 = KP_8 asterisk
keysym KP_9 = KP_9 parenleft
keysym KP_0 = KP_0 parenright
--------------------------------------------------------------------------------

Now, instead of pressing Shift+2 for the @ character, I have to press Shift+KP_2 produce the @ character.

Emacs-23 can use great (Xft) fonts too

2007-10-30T07:15:00.000-07:00

Check out the following link for details:
http://peadrop.com/blog/2007/01/06/pretty-emacs/

Basically you need to do the following if you are using ubuntu feisty like me (there is a repo for gutsy too):

Add the following lines to your /etc/apt/sources.list:
---------------------------------------------------------------
deb http://ppa.launchpad.net/avassalotti/ubuntu feisty main
deb-src http://ppa.launchpad.net/avassalotti/ubuntu feisty main
---------------------------------------------------------------

Then do a "sudo apt-get update" followed by
"sudo apt-get install emacs-snapshot emacs-snapshot-el"

This will install the required emacs package.

Then add the required font line to your ~/.Xresources file. In my case, I wanted to use "Bitstream Vera Sans Mono" at 10 points size. So I appended the following line to my ~/.Xresources file:
--------------------------------------------
Emacs.font: Bitstream Vera Sans Mono-10
--------------------------------------------

Then in order for this to take effect, I did an
"xrdb -merge ~/.Xresources".

After that I fired up emacs, and lo and behold... the world's
greatest 'editor' now with Xft font support :-)

Reason for creating this blog

2007-10-27T14:10:00.000-07:00

Whenever I have some free time, I play with my Linux box at home. During these fun times, I do some stuff, install cool software, and in the process, often figure out how to do certain things in Linux. But till now, I never noted down the successfull attempts. So I tend to forget how I did certain things in the past. This blog is an attempt to rectify that situation.

From now on, I will note down those fun moments here (... maybe even the unsuccessfull ones so that someone reading this might be able to help me out)