Linux adventures

Preserving image size while converting from PS to PDF

2011-02-12T03:49:00.001-08:00

$ ps2pdf -dEPSCrop file.ps

Working with PDFs

2010-08-15T22:58:00.000-07:00

Join PDF files using ghostscript:

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf

Merge Two or More PDFs into a New Document using PDFtk

pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf

or (Using Handles):

pdftk A=1.pdf B=2.pdf cat A B output 12.pdf

or (Using Wildcards):

pdftk *.pdf cat output combined.pdf

Processes keeping your device busy while Unmounting

2010-06-09T05:24:00.000-07:00

Many a times, when you are trying to unmount your usb device, you find it busy and can't figure out what process is keeping it busy. Some of the commands which can help you in this matter are "fuser" and "lsof". fuser displays the PID of processes using specified files or file systems. lsof list the open files. Just observe the output of my lsof command:

[Wed Jun 09|swg@insane:intel]$ lsof |grep Transcend

bash 8619 swg cwd DIR 8,17 4096 470 /media/Transcend/intel

lsof 13006 swg cwd DIR 8,17 4096 470 /media/Transcend/intel

grep 13007 swg cwd DIR 8,17 4096 470 /media/Transcend/intel

lsof 13008 swg cwd DIR 8,17 4096 470 /media/Transcend/intel

Transcend is my usb device which I want to unmount and it is giving me a 'device busy' error. I find that "current working directory" is accessing the this device apart from the other two commands about which I am aware of. Hence, I need to come out of this directory called "/media/Transcend/intel" and do an unmount on the usb device.

Printing to a Samsung SCX-4300 printer shared on Windows XP from Debian Lenny

2010-06-07T05:02:00.000-07:00

I got a Samsung SCX-4300 multi-function printer at my office. Currently, it is connected to a windows machine through a USB cable. I wanted to be able to use it as a network printer for my Debian laptop. After a bit of search on google, I could find a solution that worked for me. I must thank Anupam for helping me out during this process. I derived my understanding from this page and this article summarizes the steps that I followed.

Install "smbclient (including Samba)" and "cups" related packages using APT.
I share the printer on windows machine as "EE-Print". I connect to it through samba client using following command:

$ smbclient -L EE-Print
Enter swg's password:
Domain=[EE-PRINT] OS=[Windows 5.1] Server=[Windows 2000 LAN Manager]

Sharename Type Comment
--------- ---- -------
E$ Disk Default share
IPC$ IPC Remote IPC
print$ Disk Printer Drivers
SharedDocs Disk
G$ Disk Default share
Printer3 Printer HP LaserJet P2050 Series PCL6
Printer4 Printer Network Printer
Printer5 Printer HP LaserJet 5
F$ Disk Default share
ADMIN$ Disk Remote Admin
C$ Disk Default share
Samsung Printer Samsung SCX-4300 Series

Domain=[EE-PRINT] OS=[Windows 5.1] Server=[Windows 2000 LAN Manager]
Server Comment
--------- -------
Workgroup Master
Now we open the browser and open the CUPS web-interface by typing in the following URL:
http://localhost:631/
Now add a new printer, give a name to it and Set the device type to "Windows Printer via SAMBA".
Set the URI which includes the name that was listed earlier by smbclient, for example something like "smb://EE-Print/Samsung". If the printer is passworded, you would use something like "smb://username:password@EE-Print/Samsung".
You need to install linux driver for the printer "Samsung SCX-4300". The linux driver can be downloaded from the Samsung's official site. Untar the pack and run the "autorun" script file as a root. It has a gui interface which guides through various installation process. Currently install it as a local usb based printer.
Once you have installed the driver, restart the CUPS server and click on "modify properties" option for the printer. When it asks for a driver, then select "Samsung scx-4300 series" from the drop down menu. It will now ask for the root username and password. Remember to enter "root" in the username field and give root password in the password field.
Now you should be able to print your test page.

Reliance NetConnect Broadband on Debian Lenny

2010-04-12T08:08:00.000-07:00

Instructions for meant for people in India. Apart from the vendor information, other things should work for just anyone and anywhere.

Useful Links:

Link1. The usb_modeswitch can be downloaded from this link.
Link2.
Link3.

Basic steps are as follows:

Install usb_modeswitch package. You need to have tcl and libusb (along with the headers) installed on your system. Go through the README that comes with the usb_modeswitch package.
Plugin your reliance netconnect device and run "lsusb" to find it vendor and product id.

$ lsusb
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 002: ID 064e:a101 Suyin Corp. Acer CrystalEye Webcam
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 007 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 006: ID 12d1:140b Huawei Technologies Co., Ltd. EC1260 Wireless Data Modem HSD USB Card
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Copy following lines to /etc/usb_modeswitch.conf

# Huawei EC1260
DefaultVendor= 0x12d1
DefaultProduct=0x140b
TargetClass=0xff
CheckSuccess=20
HuaweiMode=1

I don't know much about the last 3 items. I copied the contents from a file named "12d1:1414" inside the folder /etc/usb_modeswitch.d/. Now run following command:

$ sudo usb_modeswitch -c /etc/usb_modeswitch.conf
Install the packages "wvdial" and "gnome-ppp" using synaptic manager (apt-get). You can download the packages manually as stated in the second link above. However, you may face dependency issue.
$ sudo modprobe usbserial vendor=0x12d1 product=0x140b
$ sudo wvdialconf
Now edit the file /etc/wvdial.conf and add additional lines if you have to. Some of these lines are generated automatically by wvdialconf and hence you should not delete any of these. You should add your phone number, username and password and last few lines if necessary.

[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = Analog Modem
Phone = #777
ISDN = 0
New PPPD = yes
Modem = /dev/ttyUSB0
Username = 93xxxxxxxx
Password = 93xxxxxxxx
Baud = 9600
Stupid Mode = 1
Now you should be ready to test your network connection. On a console, run the following command:
$ sudo wvdial

--> WvDial: Internet dialer version 1.60
--> Warning: section [Dialer netconnect] does not exist in wvdial.conf.
--> Warning: inherited section [Modem0] does not exist in wvdial.conf
--> Cannot get information for serial port.
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
OK
--> Modem initialized.
--> Sending: ATDT#777
--> Waiting for carrier.
ATDT#777
CONNECT
--> Carrier detected. Starting PPP immediately.
--> Starting pppd at Mon Apr 12 18:32:25 2010
--> Pid of pppd: 17509
--> Using interface ppp0
--> pppd: ��[06][08]P�[06][08]
--> pppd: ��[06][08]P�[06][08]
--> pppd: ��[06][08]P�[06][08]
--> pppd: ��[06][08]P�[06][08]
--> local IP address 115.184.110.26
--> pppd: ��[06][08]P�[06][08]
--> remote IP address 220.224.141.145
--> pppd: ��[06][08]P�[06][08]
--> primary DNS address 202.138.103.100
--> pppd: ��[06][08]P�[06][08]
--> secondary DNS address 202.138.96.2
--> pppd: ��[06][08]P�[06][08]
Keep it running on the console. You configure your network manager (system->admin->network) to use "PPP" connection as a default mode for connecting the internet. You may think of disabling other connections. For PPP connection, under general tab, check the box "Enable this connection" and select "serial modem" as the connection type. You can also fill in the phone number along with username and password. Under modem tab, it uses /dev/modem as the port (I don't know if it is correct). Under options, I have checked the box "set modem as default route to internet".

Vim, GDB

2010-03-28T22:50:00.000-07:00

In this aspect, Emacs has a better GDB interface. The best interface for using GDB with vim seems to be the clewn project. The installation is fairly easy. This page describes the process of installing and using gdb with vim. However, Clewn works only with gvim and not with vim. If you are using vim on a console, you need to recompile vim with vimgdb patch. The process is described on the Clewn webpage. You can click here . This option is little cumbersome as one has to download the source and compile it with the vimgdb patch. Since I like gvim, I prefer to use clewn.

VIM, auto Completion

2010-03-25T02:13:00.000-07:00

IF you are only interested in auto-completing long words as you type, then you look here. Basically it says :

The function A_Very_Long_Function_Name() can be quite exasperating to type over and over again. While still in insert-mode, one can auto-complete a word by either searching forwards or backwards. In function, Another_Function() one can type A_Very... and hit CTRL-P. The first matching word will be displayed first. In this case it would be A_Very_Long_Variable_Name. To complete it correctly, one can hit CTRL-Pagain and the search continues upwards to the next matching word, which is A_Very_Long_Function_Name. As soon as the correct word is matched you can continue typing. VIM remains in insert-mode during the entire process.

However, if you are interested in having declarations for all functions available in C++ or in a library, you need to use ctags. A very good explanation of the process to set it up is available here. It is quite long. I would just enumerate the steps for the sake of brevity. I tried it on both Debian 5.0 and Ubuntu 9.10 and it works perfectly.

Install exuberant-ctags

$ sudo apt-get install ctags
Download omnicppcomplete package and extract the zip file into your ~/.vim/ folder. After this .vim folder should look something like this. It may contain other folders depending on the original content of your .vim folder. IF you don't have a .vim folder in your home directory, then create now.

$ cd ~/.vim
$ ls
after autoload doc ftplugin omnicppcomplete-0.41.zip
Generate tags for C++ . ctags generates a file called "tags". You should rename it to something like "cpp.tags". You can have different such files for different libraries.

$ ctags -R --c++-kinds=+p --fields=+iaS --extra=+q /usr/include/c++
$ mv tags cpp.tags
Now add following lines to ~/.vimrc file

set tags+=~/.vim/cpp.tags
set nocp
filetype plugin on
map :!ctags -R --c++-kinds=+p --fields=+iaS --extra=+q .

Last command maps CTRL-F6 to generate tags in the current directory directly from vim editor.
Open Vim and run following command to see the help files related omnicomplete.

:helptags $HOME/.vim/doc
:h omnicppcomplete

Printing text files : a2ps

2010-03-14T22:36:00.000-07:00

Usually it is easier to convert a text file directly into PS files and then into a pdf file.

$ a2ps -R -1 -o abc.ps abc.cpp
$ ps2pdf abc.ps abc.pdf

-1 : Predefined layout: 1 x 1 portrait, 80 chars/line, major rows (i.e. alias for `--columns=1 --rows=1 --portrait --chars-per-line=80 --major=rows').

-o : Output file

Installing Debian Lenny from a USB flash disk

2010-03-08T00:38:00.000-08:00

I tried the instructions available at this link and it worked for me. I will just summarize the steps that I followed . I am assuming that your flash disk is identified as /dev/sdf by your system. (Check dmesg output). If you have a bigger disk, you can create multiple partitions using fdisk. We will use /dev/sdf1 for our discussion.

Create a Fat16 partition using fdisk. Some information about this is available here.

# umount /dev/sdf1
# mkdosfs /dev/sdf1
Use syslinux as a boot loader

# syslinux /dev/sdf1
Download the current Debian hd-media installer images from here. Download vmlinuz, initrd.gz from this page.
Download the current Debian netinstall cd image from here. Note that the versions of these two images must match.
Copy necessary files into the disk

# mount /dev/sdf1 /mnt/usb
# cp vmlinuz /mnt/usb/
# cp initrd.gz /mnt/usb/
# cp debian-504-i386-netinst.iso /mnt/usb
Create 'syslinux.cfg' file inside /mnt/usb/ containing following lines :

default vmlinuz
append initrd=initrd.gz
Now unmount the usb disk and fix or create the mbr

# umount /dev/sdf1
#install-mbr /dev/sdf
Now plug into the system where you want to install Debian. You need to select USB device as your first boot device.

Debian 5.0 Lenny

2010-02-26T17:17:00.000-08:00

I moved over from Ubuntu 9.04 to Debian 5.0 recently. It was not because I did not like Ubuntu. I think Ubuntu is simply great and it has made Linux as user friendly as Windows. But I faced problems in compiling and installing some scientific packages. Hence, I had to move over to Debian. Moreover, I had been using Debian for a long time (nearly 4 years) before switching to Ubuntu. I am quite happy to be back to Debian. The current version 5.0 is certainly better than its predecessors. GUI functions are more stable. I have all the ingredients necessary for my work. I really don't worry about having latest packages as long as the current package is stable and it works. On this aspect, I faced trouble with Ubuntu sometimes. I am planning keep updating my readers about the problems I faced with Debian 5.0 and how to get around them.

Today, I would talk about the problem of VLC player not showing the video. It happened because of debian-multimedia repository. It upgraded some codes and vlc player stopped displaying video. The solution is to remove the debian-multimedia repository from /etc/apt/sources.list and then do the following :

$ sudo apt-get update
$ apt-get remove ffmpeg libavcodec51 libavdevice52 libavformat52 libavutil49 libpostproc51 libswscale0
$ apt-get install ffmpeg libavcodec51 libavdevice52 libavformat52 libavutil49 libpostproc51 libswscale0

$ apt-get install vlc

After this, your VLC player should work normally. It worked for me.

Adobe flash on Google Chrome, Ubuntu

2010-02-25T18:08:00.000-08:00

If you are not able to see Youtube videos on Google chrome, then probably your flashplayer is not working properly.

For 64 bit machines, download the Adobe flashplayer from this link.
For 32 bit machines, download from here.

Extract from the tar ball :

$ tar -xzvf libflashplayer-10.0.45.2.linux-x86_64.so.tar.gz

make a directory :

$ sudo mkdir /opt/google/chrome/plugins

$ sudo cp libflashplayer.so /opt/google/chrome/plugins

$ google-chrome --enable-plugins

You can change this command in your application menu as described here.

Google IME for Indian Languages ...

2010-01-30T05:07:00.000-08:00

Using indian languages on a computer had never been so easy. I mean you can type directly in hindi in any windows application - notepad or word or web browser. Thanks to the google transliteration IME. You really don't need to remember the hindi key sequence (which is the case when you use window's native IME support. You can just type in the roman characters and it converts them into your native language (the same thing that happens in Gmail or in other google application. There is a free software called "Baraha" which does the same thing. I have been using this software for quite some time and I found it useful. However, its integration with other windows application is not that good.

After saying all this, I suggest you to download google transliteration IME tool from this link and see for yourself.

http://www.google.com/ime/transliteration/

Also go through the installation instruction ....

Here is a screenshot of how it looks on my computer. I advise you to enable the short-cut key for enabling and disabling google IME. The google IME icon is sitting at the bottom right corner of the screen.

In fact, I can write directly in Hindi here ... for instance ... क्या आप हिंदी देख सकते हैं ? यह बहुत अच्छा है.

Convert PS and EPS files into JPEG

2010-01-21T19:08:00.000-08:00

I got this useful information from this link.

You can convert any ps or eps file into a jpeg using ghostscript:

gs -sDEVICE=jpeg -dJPEGQ=100 -dNOPAUSE -dBATCH -dSAFER -r300 -sOutputFile=myfile.jpg myfile.eps

This method has one flaw. It produces huge files. Depending on the eps file you may get something like 2000×3000 pixels which is slightly on the insane side. Also the file size of the JPG will be about 10 times that of the eps.
We will now need to trim and resize the file using some Image Magic tools:

mogrify -trim -resize 800x600 myfile.jpg

In order to execute this command on multiple files, use following bash script

for k in $(ls *.eps); do b=`basename ${k%.eps}`; gs -sDEVICE=jpeg -dJPEGQ=100 -dNOPAUSE -dBATCH -dSAFER -r300 -sOutputFile=$b.jpg $k; mogrify -trim -resize 800x600 $b.jpg; done

Linux on windows: Cygwin

2010-01-09T19:20:00.000-08:00

If you use applications that work on only windows (like gtalk, voipcall clients), then you feel like having linux environment on the side, so that you won't have reboot into linux for doing your work. For these people (including me), Cygwin is a good choice. For instance you can have the bash shell, emacs, gnuplot, xfig, gvim, latex, xdvi all at one place ... The installations is very easy. Don't forget to install X server of cygwin (cygwin/x) during the installation process. Particularly, latex is more neat to use on cygwin than installing miktex and other tools for the same purpose.

deprecated conversion warning for char* in GCC

2009-08-23T20:12:00.000-07:00

g++-4.x gives following warning whenever a string with in double quotes is assigned to a char * :

warning: deprecated conversion from string constant to ‘char*’

Though there is no fix available as far as I know except for following two solutions:
1. convert 'char *' to 'const char*' whenever a string is to be assigned.
2. use a type cast to convert a string to a char*.

For example:

const char *name = "Adam Smith"
char *name = (char*) "Adam Smith"

To get rid of deprecated conversion warning, pass -Wno-write-strings option to g++

opencv on Ubuntu Jaunty

2009-08-23T19:49:00.000-07:00

Opencv does not handle videos properly on Ubuntu Jaunty. In order to fix this, please follow the instructions given at this link:

http://gijs.pythonic.nl/blog/2009/may/3/getting-video-io-working-opencv-and-ubuntu-jaunty-/

Vim-latex suite on Ubuntu Jaunty

2009-08-10T17:31:00.000-07:00

First install vim-latex package using synaptic packet manager. Then run following command on a terminal :

$ sudo vim-addons -w install latex-suite

Now opening a tex document with gvim should show tex related menus on the menu bar.

If this does not help, then refer to ubuntu forums for solution. For instance check this link.

Automating chmod

2009-07-10T02:56:00.000-07:00

Task is to change the permission modes for multiple directories

$ find . -type d -print0 | xargs -0 chmod 771

PDF Highlighting tool

2009-06-30T04:13:00.000-07:00

Earlier I talked about few tools for editing PDF files (for free) on linux. You can go through the discussion here. I recently came across some more free tools that tend to make our life little easier, particularly when it comes to editing pdf files on linux. Some of these tools are as follows:

Scribus : Limited capabilities
Inkscape : Limited capabilities
Okular : Limited capabilities. You can do some highlighting and add annotations. But they don't seem to be very neat. Just give a look at some screenshots.
PDF-xchange-viewer. Its a windows based application which is free to download at present and can be run on linux using Wine. I could use it flawlessly on my Ubuntu Intrepid Ibex (8.10). Among all pdf editing tools, this seems to the best option for editing pdf files. Even though its not a native linux application, it is better than going back to windows just for editing a PDF file. However, I am still waiting for GNUpdf which, I believe, would provide a permanent relief to linux users in this regard.

To get started, first use synaptic packet manager to install wine. For Ibex, follow the instructions given at this link. Download PDF-xchange-viewer from its website and run it using wine. That's all. It installs itself within a folder. A screenshot of PDF-xchange-viewer is shown in the adjacent thumbnail. Its really neat and close to what we find in Adobe Acrobat PDF editor.
PDFescape: You can edit PDF files online (particularly fill up forms) at this website. This is useful if you are in a hurry and can't install a PDF editing software on a public machine.

Installing Essential softwares on Debian Etch

2009-01-20T20:14:00.000-08:00

In order to install softwares like acroread and mplayer, include following line into your '/etc/apt/sources.list'

deb http://www.debian-multimedia.org/ etch main

Download the key-ring from this site and install it as follows:

$ sudo dpkg -i debian-multimedia-keyring_2008.10.16_all.deb

and then run "apt-get update". More information regarding this is available here and here.

# sudo apt-get install acroread

For flash, you need to install the package "flashplugin-nonfree" which is available in backports repository. Include following line into your sources.list file:

deb http://www.backports.org/debian etch-backports main contrib non-free

and now get keyrings for backport repository.

#apt-get install debian-backports-keyring
#apt-get update
#apt-get -t etch-backports install flashplugin-nonfree

Mounting an external drive using volume label

2008-12-04T10:53:00.000-08:00

The device nodes keep changing if you are pluggin in and out several different usb disks and in different orders. For various reasons for instance for file synchronization, it is useful to mount these drives according to their names.

First of all, find out the correct device partitions for usb drives.

$ sudo fdisk -l
Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x4be002e1

Device Boot Start End Blocks Id System
/dev/sda1 1 1402 11261533+ 12 Compaq diagnostics
/dev/sda2 * 1403 15918 116592640 6 FAT16
/dev/sda3 15918 29975 112918572 f W95 Ext'd (LBA)
/dev/sda4 29976 30402 3420160 12 Compaq diagnostics
/dev/sda5 15918 22292 51200000 7 HPFS/NTFS
/dev/sda6 22293 22304 96358+ 83 Linux
/dev/sda7 22305 22912 4883728+ 82 Linux swap / Solaris
/dev/sda8 22913 26559 29294496 83 Linux
/dev/sda9 26560 29975 27438988+ 83 Linux

Disk /dev/sdb: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x5b6ac646

Device Boot Start End Blocks Id System
/dev/sdb1 1 24315 195310206 c W95 FAT32 (LBA)
/dev/sdb2 24316 38913 117258435 82 Linux swap / Solaris

The Usb disk is mounted at /dev/sdb.

Before changing the label, unmount the device partitions. This is very important.

$ sudo umount /dev/sdb1
$ sudo umount /dev/sdb2

Install "mtools" and "e2fsprogs"

$ sudo apt-get install mtools e2fsprogs

in order to label vfat partitions, we need 'mtools' and 'e2label' is needed for labelling ext2/3 partitions.

$ sudo mlabel -i /dev/sdb1 -s :: SWG_WIN

now check the label with following command

$ sudo mlabel -i /dev/sdb1
Volume label is SWG_WIN

$ sudo e2label /dev/sdb2 swg_lin

check the label using following command:
$ sudo e2label /dev/sdb2
swg_lin

Now edit /etc/fstab and enter following lines:

LABEL=SWG_WIN /mnt/usb_win vfat user,rw,auto,umask=0 0 0
LABEL=swg_lin /mnt/usb_linux ext3 user,rw,auto 0 0

save the file and remount them

$ sudo mount -a

More information about changing partition labels are given here.

Drawing Rectangles in GIMP

2008-11-30T05:17:00.000-08:00

Select a rectangular region by clicking "Rectangle Select Tool". Then click on Edit -> stroke selection. Inside this tool, you can select different line styles like continuous, dashed etc. In order to change color of the line, click on "Foreground and background color" item available in Gimp's main menu. More elaborate discussion is available in the following link:

http://pbs01.wordpress.com/2007/09/30/145/

Setting UP NFS server/client on Ubuntu

2008-11-22T21:55:00.000-08:00

Install NFS Server Support

This is mostly a local copy of the instructions available at this link. I have tried this howto and it works perfectly for me.

at the terminal type
sudo apt-get install nfs-kernel-server nfs-common portmap
When configuring portmap do =not= bind loopback. If you do you can either edit /etc/default/portmap by hand or run:
sudo dpkg-reconfigure portmap
sudo /etc/init.d/portmap restart

Editing /etc/exports
the /etc/exports file is used for creating a share on the NFS server

invoke your favorite text editor or
sudo vi /etc/exports

Here are some quick examples of what you could add to your /etc/exports

For Full Read Write Permissions allowing any computer from 192.168.1.1 through 192.168.1.255

/files 192.168.1.1/24(rw,no_root_squash,async)

Or for Read Only from a single machine

/files 192.168.1.2 (ro,async)

save this file and then in a terminal type
sudo /etc/init.d/nfs-kernel-server restart

Also aftter making changes to /etc/exports in a terminal you must type
sudo exportfs -a

Install NFS client support
sudo apt-get install portmap nfs-common

Mounting manually
Example to mount server.mydomain.com:/files to /files. In this example server.mydomain.com is the name of the server containing the nfs share, and files is the name of the share on the nfs server

The mount point /files must first exist on the client machine.
cd /
sudo mkdir files

to mount the share from a terminal type

sudo mount server.mydomain.com:/files /files

Note you may need to restart above services:
sudo /etc/init.d/portmap restart
sudo /etc/init.d/nfs-common restart

Mounting at boot using /etc/fstab
Invoke the text editor using your favorite editor, or
gksudo gedit /etc/fstab

In this example my /etc/fstab was like this:

server.mydomain.com:/files /files nfs rsize=8192,wsize=8192,timeo=14,intr

You could copy and paste my line, and change “servername.mydomain.com:/files”, and “/files” to match your server name:share name, and the name of the mount point you created.
It is a good idea to test this before a reboot in case a mistake was made.
type
mount /files
in a terminal, and the mount point /files will be mounted from the server.

Gtalk Voice chat on Ubuntu

2008-11-22T21:50:00.000-08:00

After such a long wait, today I could talk to one of my friend in India through Gtalk on linux. I am talking about voice chat. I am very much impressed with Ubuntu. Its amazing. Things had never been so easy and comfortable.

Presently Empathy supports voice calls through gtalk. The installation instructions are available here. Just for convenience, I am reproducing the set of instructions necessary to get you started with it. Visit the above site for user comments and more information if things don't work out for you.

Use Synaptic package manager, go to Settings->Repositories->Third Party Software and then click Add and add the following line

deb http://ppa.launchpad.net/telepathy/ubuntu hardy main

Then, Install the following packages using Synaptic Pagakage manager.

Empathy
telepathy-gabble
telepathy-mission-control
telepathy-stream-engine

After successful installation, open the Empathy application and use the menu, Edit->Accouts to add your gtalk account. Enjoy using voice chat with your favorite gtalk account using Empathy in Linux.

Data Backup and File synchronization

2008-10-07T18:15:00.001-07:00

If you work on multiple systems like a desktop in office and a laptop in house, probably you would like to synchronize the files between the two. So far I have been using rsync to copy files from my laptop to a usb disk and then using this disk to synchronize data on my desktop at office. While rsync is faster and does not require much configuration, it is good for one way data transfer. But some time you end up with multiple copies or backing up unnecessary data files. For instance if you delete a file in one, you must do the same on the another simultaneously. Probably it can be solved by properly configuring rsync, but certainly its not straight forward for a normal user. Recently I used gui based tool like Unison for file synchronization. I found it pretty much user friendly as it reports the conflicts and allows the user to decide what to do about it. Another tool that I found useful is sBackup for creating backup of important files on your system. These days our work and life depend too much on digital media. Hence backing them up against inadvertent system crashes or human errors, has become very much crucial. sBackup provides a simple gui to configure and setup backup process. You can have complete control over the files you want to backup. You can exclude files based on extension or size. You can set how frequently backup must be taken and you can get rid of old backups which are no more relevant.

In short, file synchronization and backing up data is no more daunting on Linux.

Ubuntu - Most popular Linux

2008-10-03T05:39:00.000-07:00

According to distrowatch, Ubuntu is the most popular linux distribution at the moment. I have used several distributions over the years like mandrake, redhat, fedora, debian. For last 2/3 years, I have been using Debian regularly and Fedora intermittently. However, one thing that annoyed me in Debian was its outdated packages. However I was afraid of going to Ubuntu as I thought it would be unstable and it would keep crashing all the time. After going through the reviews, I thought of giving it try.

You won't belive, I was just overwhelmed at its first performance. All of my hardwares got working during the first install itself ... installing flash, media players, java plugin was as simpler than writing this blog itself ... Suddenly my system looked all new and fresh ... I thought speed would be less, but I was wrong again ... It was amazingly fast ...

No wonder why Ubuntu is No. 1 Linux distro. You must give it a try ...

Some later additions:

Until now I preferred command line interfaces (CLI) for configuring applications like network setting, installing/uninstalling softwares, browsing and even cd writing. Its because I relied less on gui system. However after moving to Ubuntu, I started using much of gui stuff.
Secondly, the ubuntu forums are very good in the sense that I could get rid of most of my problems in a very short time.
Barring few glitches here and there, I found Ubuntu quite user friendly and easy to use.

APT - Pinning in Debian

2008-09-26T12:06:00.000-07:00

Even though I myself use Debian, I suggest Fedora to others. Its because, most of these people are interested in packages than the OS. Fedora comes with all the latest packages and has a user friendly interface for most configuration tasks. Though I think, ubuntu is a good competitor to Fedora in this aspect. Since I have spent quite a lot of time with Debian (say 3 years), I find Debian more stable and easier to manage than other distros. Most of the available packages on Etch just work fine with no hiccups. The only drawback seems to be the fact these packages are outdated. If you are really not keen on new features and happy with the available features, then Debian Etch is the right choice. Because its really stable and it works without any problem on most of the systems. But many a times, you just can't do without newer packages. One way would be to go for Debian testing or unstable repositories. But I would be prefer a stable system with less number of new packages than an unstable system with many new packages. This is where APT Pinning comes into picture. This is about finding the right combination of all the repositories. Here the administrator can consciously decide where to put the line between stability and the availability of new packages.

More information on APT - Pinning

Could not start kstartupconfig on Debian Etch 4.0

2008-09-26T08:26:00.000-07:00

Today one of my fellow labmates asked me whether he can use KDE on his laptop. I installed debian on his system sometime back. If you are installing on a new system, then I would suggest you to get a Debian KDE CD image, but if you want to install kde on your existing debian system that you installed using default Debian CD image, then you can read the rest of the article:

$ apt-get install kdm kde-core

However when I log out and login again by choosing KDE as my window manager, I get following error:

could not start kstartupconfig. Check your installation.

One solution that worked for me is this:

$ sudo chown -R username:users /home/username

'username' is the login name for the current user. After that I logged out and logged in again to get a working KDE session.

Resizing image using GIMP

2008-09-22T16:07:00.000-07:00

A lot of information is available on web about how to use GIMP and hence I would be very precise and brief in my description. Basically, I am interested in reducing the resolution of the image without changing its print size. For this, you need to remember this formula:

Print size = No. of Pixels / Resolution

So, for different resolution, we need to choose different of pixels so that the size remains same. The formula would be

NoP_1 / Res_1 = NoP_2 / Res_2

So, the new number of pixels for new resolution would be given by

NoP_2 = Res_2 * NoP_1 / Res_1

Load a new image onto GIMP from File -> Open menu and then go to view -> Info Window to know about current size and resolution. Now go to button Image -> Scale Image window and reduce the x and y resolution to a lower value and compute the x size and y size (in pixels) for this new resolution using above formula and change them accordingly. Then save the file in your desired format.

Editing PDF on Linux

2008-09-11T04:03:00.000-07:00

I have been badly looking for a tool that can annotate, highlight a PDF file. Its because I need to read a lot of technical papers and I love to highlight the main points in that paper so that I wont' have to search for those key points. I did not want to jump to windows and install a pirated Adobe software to do the job. I wished if open source guys could help me in this regard. After saying that let me tell you I am desperately waiting for the first release of GNUpdf. Until it comes out, I have been looking for alternatives. Among various solutions, I would talk about only two options that I found useful:

1. PDFedit. The only full-fledged pdf editor available for linux. However, it has many caveats and I hope new releases of this software solve the problems. One of the problems that it does not edit many files saying the document is "read-only". Even though I set the option "allow editing read-only files" in Tools->option, still it does not work. Secondly, pdfedit freezes for few seconds during highlighting text.

2. Xournal. It seems to be a better option for highlighting and annotating PDF files. This page talks about configuring xournal for highlighting function. The interface is smooth and things seem to work for the time being. I would post more on this when I try them out.

Some other tools for editing PDF files on Linux are as follows:

Now that I tried xournal, I must say its pretty good. At least it is not that buggy as compared to PDFedit. But PDFedit has more features and we can expect to get good behaviour in future releases. But as far as highlight and annotating is concerned, I am happy with xournal. Just see a snapshot of xournal window.

Printing on a HP LaserJet over the network using Linux

2008-08-16T04:39:00.000-07:00

The desktop given to me is connected to a printer HP Laserjet 2200 over network with an IP address. I wanted to configure it on Fedora. I already know about the fact that HP printers are well supported on Linux. This post might help you if are in similar kind of situation, that is, you want to connect to a network printer from a linux box over LAN. This post is only for the sake of convenience. If things don't work out and you need more information then you should visit this link.

Lets first see the system configuration.

$ uname -a
Linux localhost.localdomain 2.6.25.14-108.fc9.x86_64 #1 SMP Mon Aug 4 13:46:35 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux

So, basically I am using FC9 with x86_64 processor. This much is good enough for us.

Check if cups daemon is running. You can check at System->Administration->Services->Cups. It should be running. You can also check this on console using following command:

$ sudo /sbin/chkconfig --list|grep cups
cups 0:off 1:off 2:on 3:on 4:on 5:on 6:off

So, Cups is running on run-level 3, 4 and 5. If it is not running, then you should make it run first. Its not dificult and following command should do the job.

$ sudo /sbin/service cups start
or
$ sudo /sbin/chkconfig --level 345 cups on

Now, check if hplip is available on your system.

$ rpm -qa|grep hplip
hplip-2.8.2-2.fc9.x86_64
hplip-gui-2.8.2-2.fc9.x86_64

In case they are not present, use Yum to get the required packages:

$ sudo yum install hplip hplip-gui

If HPLIP is already installed then try running hp-setup to configure your printer.

$ sudo hp-setup

I choose the second option 'Network connection'. Then click on next.

It lists the printers available on the network. I choose the the HP LaserJet 2200 that is assigned to me and then click next.

It asks me to select a suitable PPD file available in the list. Usually you should select the one that closely matches the description of the printer. In this case I retain the first selection.

Here I add some description to my printer and click next. On the next screen it sends a test page for printer. It starts working !! I did not believe that the things would be this much simple. Because I remember spending days on getting my printer work on linux. I think those days are gone now. The life has certainly become more comfortable with linux.

Remote Access on Linux

2008-07-06T11:31:00.000-07:00

VNC server and vncviewers are quite popular for accessing linux desktops remotely either from a windows or a linux client. I won't discuss much about them as a lot of information is available on web about this. I would rather give links to some webpages here:

Rather than explaining things, I would just write down few commands to get you started. I am assuming you are using Debian Etch 4.0.

$ sudo apt-get install vncserver

$ vncserver :1 -geometry 1024x768 -depth 24 -pixelformat rgb565

It might ask you to enter a password to be used by users to connect your system through vnc.

The first time vncserver is started up, it will also create a configuration file, in your home directory, called

$HOME/.vnc/xstartup. Execute the follow to stop vncserver.

$ vncserver -kill :1


On your client,

$ vncviewer :1

Best part is you can connect to a vncserver through an SSH tunnel using -via option with vncviewer. But install tightvncserver on the host machine. In order to use ssh tunnel, you need to provide username and password for ssh login. so the first password is for ssh login while the second password is for vncserver available in ~/.vnc/passwd. -Fullcolor option gives best display property for your vnc session.

[control@cube:]$ vncviewer -via swg@172.28.52.111 -Fullcolor insane:1

VNC Viewer Free Edition 4.1.1 for X - built Feb 26 2007 20:38:07
Copyright (C) 2002-2005 RealVNC Ltd.
See http://www.realvnc.com for information on VNC.
swg@172.28.52.111's password: ***

Sun Apr 27 12:24:43 2008
CConn: connected to host localhost port 5599
CConnection: Server supports RFB protocol version 3.3
CConnection: Using RFB protocol version 3.3
Password: ***

Sun Apr 27 12:24:45 2008
TXImage: Using default colormap and visual, TrueColor, depth 24.
CConn: Using pixel format depth 24 (32bpp) little-endian rgb888
CConn: Using ZRLE encoding

Sun Apr 27 12:24:52 2008
CConn: Throughput 20000 kbit/s - changing to hextile encoding
CConn: Using hextile encoding

Connecting a Linux server from a windows client

2008-07-06T04:23:00.000-07:00

There are two ways we can connect a linux machine from windows:

1. Using Putty to establish a ssh connection and exporting display using xmanager

2. Using VNC client to connect to vnc server running on linux machine.

I would describe both the methods as neatly as possible.

Putty+ Xmanager

1. Download "Xmanager" from this site.

http://www.netsarang.com/download/down_xme2.html

2. Install the Xmanager Enterprise 2.1 Build 0038 . In the serial
field type "evaluation".

3. Once installation is over, go to start -> all programs -> Xmanager
Enterprise -> xmanager-passive

4. Now run "putty.exe". Enter the IP of the ssh server you want to
connect. Click on connection -> ssh -> x11 on the left hand side bar
and on the right hand side click on "Enable X11 forwarding".

5. Now login to your ssh server and run any gui application.

VNC Server - client

1. Download realvnc viewer from this site. It would ask you to enter
user info. Don't enter anything and click on "proceed to download".

http://www.realvnc.com/products/free/4.1/winvncviewer.html

2. Download the following exe file and NOT the zipped one and put it on desktop.

VNC Free Edition Viewer for Windows
Stand-alone Viewer
Version 4.1.2

3. Double click on it. It would ask for Server. Enter following

your_vnc_server:1

4. Then it will ask for password only. Now enter the password provided to you.

5. Enter the password and you can the linux desktop.

Caution: First try to connect the vncserver from a linux desktop and make sure that it is working. Then only try from a windows machine.

Renaming multiple files on Linux

2008-06-05T20:29:00.000-07:00

The syntax for the rename command is:

rename [ -v ] [ -n ] [ -f ] perlexpr [ files ]

-v : verbose

-n : test run

perlexpr: perl regular expression

Example 1: change "*.htm" to "*.html"

$ rename -n ’s/\.htm$/\.html/’ *.htm

s - substitute : s/old/new

$ - end of string. That is search for only '.htm', not '.html'

Example 2: change filenames that have the pattern ########.JPG (8 numbers and capital .JPG) to something like BeachPics_########.jpg

$ rename -n 's/(\d{8})\.JPG$/BeachPics_$1\.jpg/' *.JPG

00001111.JPG renamed as BeachPics_00001111.jpg
00001112.JPG renamed as BeachPics_00001112.jpg
00001113.JPG renamed as BeachPics_00001113.jpg

\d{8} : count 8 digits

(\d{8}) : Parenthesis is meant to save this as an argument for later use

$1 : insert the string from the first set of parenthesis - in this case the 8 digits

$ rename -n 's/\d{5}(\d{3})\.JPG$/BeachPics_$1\.jpg/' *.JPG
00000123.JPG renamed as BeachPics_123.jpg
00000124.JPG renamed as BeachPics_124.jpg
00000125.JPG renamed as BeachPics_125.jpg

Example 3: replace 'weight_' to 'ffn_wt_' in all the files

$ rename -n 's/weight_*/ffn_wt_/g' *.txt
weight_far.txt renamed as ffn_wt_far.txt
weight_near.txt renamed as ffn_wt_near.txt
weight_top.txt renamed as ffn_wt_top.txt

Bash History

2008-05-28T07:17:00.000-07:00

During last 5 years of using Linux, bash has been the application I used most. Yet, I know little about it. As I am writing more and more commands on the console, I am feeling a need for efficiency. This forced me to dig more into bash and its power! But as we all know, people have already done the hard work and kept things ready for us to make use of them.

In this article I would take about Bash history commands and how to efficiently use them. I won't do much apart from providing some good links in this regard:

Summary of some commands:

Bash History

!! - repeat last command
!foo - repeat last command starting with 'foo'
CTRL + R - command auto completion
history - prints a numbered list of previously typed commands
!N - executes Nth command in the history list
!foo:p - prints a command without executing it
!$ - last argument (word) of the previous command
!* - all arguments of previous commands
^error^correction - re-executes previous command by replacing 'error' with 'correction'

Home / END

CTRL + a - beginning of a line
CTRL + e - End of a line
CTRL + w - erase a word
CTRL + u - erase from here to the beginning of the line

Modifying History behaviour

$ export HISTFILESIZE=500
$ export HISTIGNORE="&:[ ]*:exit"
            This ignores repeated commands, commands that start with a space and 'exit' and they are not added to bash history

$ shopt -s histappend 
$ shopt -s histverify
            allows users to verify a substituted history expansion.

$ shopt -s histreedit
            allows users to re-edit a failed history substitution

Put these lines into .bashrc file so that you won't have to type them again and again

Tryst with Xmgrace

2008-03-11T04:10:00.000-07:00

Xmgrace is a great WYSIWYG 2D plotting software available with GNU/Linux. Unfortunately it does not support 3D plotting at the moment. If you want to produce good quality graphs for technical papers, you should try your hands at it.

Typesetting

Grace permits quite complex typesetting on a per string basis. Any string displayed (titles, legends, tick marks,...) may contain special control codes to display subscripts, change fonts within the string etc.

Example:

F\sX\N(\xe\f{}) = sin(\xe\f{})\#{b7}e\S-X\N\#{b7}cos(\xe\f{})

prints roughly

                       -x
     F (e) = sin(e)·e  ·cos(e)
      x

using string's initial font and e prints as epsilon from the Symbol font.

NOTE: Characters from the upper half of the char table can be entered directly from the keyboard, using appropriate xmodmap(1) settings, or with the help of the font tool ("Window/Font tool").

Control code	Description
\f{x}	switch to font named "x", e.g. \f{Times}
\f{n}	switch to font number n
\f{}	return to original font
\R{x}	switch to color named "x"
\R{n}	switch to color number n
\R{}	return to original color
\#{x}	treat "x" (must be of even length) as list of hexadecimal char codes
\t{xx xy yx yy}	apply transformation matrix
\t{}	reset transformation matrix
\z{x}	zoom x times
\z{}	return to original zoom
\r{x}	rotate by x degrees
\l{x}	slant by factor x
\v{x}	shift vertically by x
\v{}	return to unshifted baseline
\V{x}	shift baseline by x
\V{}	reset baseline
\h{x}	horizontal shift by x
\n	new line
\u	begin underline
\U	stop underline
\o	begin overline
\O	stop overline
\Fk	enable kerning
\FK	disable kerning
\Fl	enable ligatures
\FL	disable ligatures
\m{n}	mark current position as n
\M{n}	return to saved position n
\dl	LtoR substring direction
\dr	RtoL substring direction
\dL	LtoR text advancing
\dR	RtoL text advancing
\x	switch to Symbol font (same as \f{Symbol})
\+	increase size (same as \z{1.19} ; 1.19 = sqrt(sqrt(2)))
\-	decrease size (same as \z{0.84} ; 0.84 = 1/sqrt(sqrt(2)))
\s	begin subscripting (same as \v{-0.4}\z{0.71})
\S	begin superscripting (same as \v{0.6}\z{0.71})
\T{xx xy yx yy}	same as \t{}\t{xx xy yx yy}
\Z{x}	absolute zoom x times (same as \z{}\z{x})
\q	make font oblique (same as \l{0.25})
\Q	undo oblique (same as \l{-0.25})
\N	return to normal style (same as \v{}\t{})
\\	print \
\n	switch to font number n (0-9) (deprecated)
\c	begin using upper 128 characters of set (deprecated)
\C	stop using upper 128 characters of set (deprecated)

Putting Symbols into Axis labels:

If you need special characters or special formatting in your label, you can use grace escape sequences (the sequence will appear verbatim in the text field but will be rendered on the graph), see typesetting above. If you don't remember the mapping between alphabetic characters and the glyph you need in some specific fonts (mainly symbol and zapfdingbats), you can invoke the font tool from the text field by hitting CTRL-e. You can change fonts and select characters from there, they will be copied back in the text field when you press the "Accept" button. Beware of the position of the cursor as you enter text or change font in the font tool, the character or command will be inserted at this position, not at the end of the string!

Note that you should see \f{Symbol} in the Cstring field of font tool when you select a symbol. In case you don't, write down manually and then click on a symbol you wish to insert and then press 'Accept'.

overlaying graphs

Begin by selecting Main:Edit/Overlay graphs to bring up the Overlay widget.
Select the graph numbers with which we would like to deal. In this example, we will overlay graph 1 onto graph 0. At this point, only graph 0 is visible. We cannot see Graph 1 to select since it does not exist at this point. We need to create simply by pressing mouse button 3 in a graph list window and selecting create new.
The overlay type is determined by what is common among the overlayed graphs. In our example, the x axis is common so we will select X-axes same, Y-axes different. This is important because we don't want to alter any axes of the Overlay graph which we set the same as the underlay graph. In this example, we don't want to alter the x-axis of graph 1.
We are now ready to label the graph axes and read the data. One thing we must be careful to do is to always make sure that we are working on the intended graph. Seeing as the graphs are overlain, clicking within the frame is ambiguous as to what graph is selected. The rule is that in a region of overlay, clicking will cycle between the graphs. Hence, if graph 1 is selecting, clicking within the frame will toggle to graph 0.
Making sure that graph 0 is active, bring up the Axis properties widget. Now set the y axis title to Gnus.
Select graph 1 as active as set the title as Gnats. Notice how it overlaps the Gnus. We want to put this on the right side. From the axis label and bar tab, select label Properties/Side=Opposite.
Label the x axis to label it. If graph 1 is the current graph, noticed how it is greyed out because only 1 x axis need be active. Select graph 0 and you should now be able to alter the axis label.
You are ready to read in data. Just make sure the graph that is active when you read in the data (or create your set) is the one in which you intend it to go.

Installing Matlab 7 on Fedora 7

2008-03-08T21:18:00.000-08:00

I will just list common problems and their probable solutions.

Problem 1: The installer does not work.
http://www.mathworks.com/support/solutions/data/1-12E9FJ.html?solution=1-12E9FJ

libXp.so.6: cannot open shared object file: No such file or directory

You need to install "libXp-devel" package.

# yum install libXp-devel

Problem 2: Why does MATLAB fail to launch on Linux machines with an error about Assertion `c->xlib.lock' failed

http://www.mathworks.com/support/solutions/data/1-54UIFE.html?solution=1-54UIFE

Problem 3: When launching matlab, you may get following error

error while loading shared libraries: /usr/local/matlab73/bin/glnx86/libmwlapack.so: cannot restore segment prot after reloc: Permission denied

There are two solutions - first, you disable SELINUX. The other solution is to allow the permission in SELinux administration itself.

Open the SELinux Administration GUI and set the following Memory Protection Boolean to true.

Allow all unconfirmed executables to use libraries
requiring text relocation that are not labeled texttrel_shlib_t

.

or run following command on console

# chcon -t texrel_shlib_t /usr/local/matlab2006b/bin/glnx86/*.so

Microphone not working on Debian Etch

2008-03-01T07:58:00.000-08:00

I use alsa driver for my sound card. Sound works perfectly. However, microphone did not work for me. I could finally got it working after little exercise. Here is what I did.

If you are using gnome, then open "gnome-volume-control".

$ gnome-volume-control &

Edit -> preference -> click on 'microphone' and 'capture'. Now make sure the microphone and capture switches are un-muted. Don't close this window and open gnome-sound-recorder.

$ gnome-sound-recorder &

Click on the record button and say something on the mic. You should be able to hear your voice once you play the recorded file. If everything goes well, then save the settings.

$ sudo alsactl store

Voice Chat on Linux

2008-02-29T23:04:00.000-08:00

I am looking for a solution for Linux. Very lately I have realized the power of voice chat. I am frequently carrying out research discussions with my guide who is right now abroad and he is going to be there for a long time. Everytime he wishes to chat with me, I am forced to switch to an windows machine where gtalk is installed.

I tried my hands at Kopete, pidgin, ekiga, jabbin, gaim, psi etc. without much success. While text messaging is supported, I failed to configure voice chat on it. I know that voice chat is supported on skype. However, I don't want to create another account for it. Moreover I am google fan and won't like to switch over to skype so soon. I would keep updating this thread about the improvements I made in this regard.