LINUX CLUES

Split a Media Video File (AVI, FLV,...) using Mencoder and Mplayer

2012-01-05T06:09:00.010+01:00

Mencoder is a movie encoder program that allows us to split a media video(e.g AVI) file into several AVI files.

We are going to split a media video file maintaining same video and audio codecs.

As mencoder accepts other file formats than avi files, we will be able to split them too, but result will be avi files.

SPLIT ONE FILE INTO TWO

E.g: We are going to split foo.avi file into foo1.avi(600 seconds long) and remaining length in foo2.avi.

Following mencoder man page advice, we could try these options:
$ mencoder foo.avi -o foo1.avi -oac copy -ovc copy -endpos 600
$ mencoder foo.avi -o foo3.avi -oac copy -ovc copy -ss 600

mencoder options:
Read more »

Swapping on a File in Linux

2012-01-04T09:37:00.003+01:00

This article shows how to create a standard file and configure your linux based system to activate swapping or paging on it.

CREATE THE SWAP FILE

First we create the swap file using dd command. cp is not useful here because swap file has not to contain holes.
# dd if=/dev/zero of=/mnt/swapfile bs=1M count=200 # We create a swap file of 200MByte in size.

For safety we disallow other users to read and modify the file:
# chown root.root /mnt/swapfile
# chmod 600 /mnt/swapfile

Swap size is unlimited for linux kernels after 2.3.3
Kernels after 2.4.10 support up to 32 swap areas.

SET UP THE SWAP FILE
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Git Command Quick Reminder

2011-12-24T18:28:00.006+01:00

INSTALLING GIT
$ aptitude install git-core # git basic tools.

gitk graphic tool.
$ aptitude install gitk # this graphic tool allows us to browse a git repo.

INITIALIZE A REPOSITORY

$ git init # Creates an empty repository in current directory, or reinitializes an existing one.
$ git init directory_name # Creates an empty repo in directory_name directory.

$ git clone remote_url # clone a remote repo. Passing as argument a local directory this command clones a local repo.

$ git clone source_repo dest_repo # clones a local repository source_repo in another local repository dest_repo,
if both are directories.
$ git clone file:///path/to/source/repo file:///path/to/dest/repo # another way to specify local directories.
This way we are sure git does not use hard links when cloning source repo.
$ git clone --no-hardlinks source_local_repo dest_local_repo # clone a repository and copy object files instead of using hardlinks for local repo objects.

GIT SVN
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My .emacs configuration file

2011-08-04T05:24:00.005+02:00

This post describes my .emacs configuration file.

.emacs configuration file is loaded by emacs editor when it starts.

Let's divide the .emacs configuration file into parts to describe it better:

Customized variables
Install user customizations of variable values specified in arguments.

(custom-set-variables
  ;; custom-set-variables was added by Custom.
  ;; If you edit it by hand, you could mess it up, so be careful.
  ;; Your init file should contain only one such instance.
  ;; If there is more than one, they won't work right.
 '(column-number-mode t)
 '(desktop-save-mode t)
 '(display-battery-mode t)
 '(display-time-24hr-format t)
 '(display-time-day-and-date nil)
 '(display-time-mode t)
 '(fringe-mode 0 nil (fringe))
 '(menu-bar-mode nil)
 '(network-speed-format-string " [%NI %AX %AB] ")
;; '(network-speed-interface-list (list "eth0" "eth1"))
 '(network-speed-interface-list (list "eth1"))
 '(network-speed-precision 1)
 '(network-speed-update-interval 2)
;; '(org-agenda-files (quote ("~/org/task_list.org")))
 '(scroll-bar-mode nil)
 '(size-indication-mode t)
 '(tool-bar-mode nil)
 '(tooltip-mode nil)
 '(w3m-session-load-last-sessions t))

Calculate Prime Numbers using an ARDUINO Board

2011-07-20T19:57:00.001+02:00

Following example uses an Arduino board to calculate a prime number list, starting from one.
It shows the result using serial port communication.

BUILDING AND RUNNING THE CODE

You should copy this code into your Arduino IDE window, compile it (C-R), upload the code into the board (C-U) and to see the result open the serial monitor (C-Shift-M).

If everything goes fine your serial monitor will show a prime on each line every time it is calculated. Maximum prime able to be calculated depends on long type maximum value.

long number = 3;

void setup()
{
  Serial.begin(9600);
  Serial.println("#");
  Serial.println("1");
  Serial.println("2");
}

void loop()
{
  int is_prime = 1;
  long i = 3;
  long top = sqrt(number);
  while (i<top)
  {
    if (number%i == 0)
    {
      is_prime = 0;
      break;
    }
    i++;
  }
  if (is_prime)
  {
    Serial.println(number,DEC);
  }
  number += 2;
}

Within setup function, it shows 1 and 2 primes. It then starts calculating in the main loop using number 3.

Primality test here consists on performing divisions and checking the remainder. It is not needed to test with every divisor, when square root is reached we know it is a prime.

When a prime number is found it is sent over serial line.

As we start calculations with number three, we can skip all even numbers.

Install and run a program in Arduino using 64 bits Ubuntu (lucid) distro

2011-07-06T19:32:00.003+02:00

From Arduino home page:
Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software.

Arduino provides a Java based IDE and examples are written in C language: http://arduino.cc/en/Reference/HomePage

MY SYSTEM consists on:

Arduino Duemilanove: An ATmega328 running at 16 MHz with auto-reset. It connects to the computer using a USB cable.

Ubuntu distro:
Release: 10.04
Codename: lucid

Linux kernel
2.6.32-32-generic
x86_64 AMD 64 bits architecture.

INSTALLING ARDUINO IDE SOFTWARE

First we install needed dependencies:

openjdk-6-jre
avr-gcc (aka "gcc-avr")
avr-libc

NOTE: On the contrary to what Arduino page said, I did not need avr-gcc-c++.

$ sudo aptitude install openjdk-6-jre gcc-avr avr-libc
NOTE: gcc-avr version is 4.3.4 in my system

DOWNLOADING ARDUINO IDE
Read more »

Installing and Configuring ANYTHING.EL for Emacs

2011-04-25T19:31:00.005+02:00

anything.el is an application framework written by TamasPatrovics (current maintainer is rubikitch).
It provides a better way to choose between alternatives when typing a command, switching buffers, searching for help, files, etc.
After you select a candidate option from the list anything provides, you can choose between several actions.

DOWNLOAD ANYTHING
We are going to download anything from its source code repository.
$ cd ~/.emacs.d
$ git clone git://repo.or.cz/anything-config.git

CONFIGURE .emacs FILE

;; Anything.el
(add-to-list 'load-path "~/.emacs.d/anything-config/")
(add-to-list 'load-path "~/.emacs.d/anything-config/extensions/")
(require 'anything-startup)

That it is enough for using anything:
e.g: M-x anything

Also common functions like switch-to-buffer are automatically remapped to anything ones.

However you could also customize your anything buffers, selecting the anything sources you want:
Read more »

Simple Python IRC Bot

2011-03-19T19:05:00.009+01:00

This article shows the code of a simple python irc bot.

To run it, you should create a file, e.g: pybot.py, copy following code in it, and exec:
$ python pybot.py

other way to run it:
$ chmod a+x pybot.py
$ ./pybot.py

BOT SOURCE CODE
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Calculate prime numbers using PHP

2011-01-27T03:09:00.004+01:00

Simply create a file named primeNumberCalculator.php. Copy following text in it.

You need a web server supporting php scripting.
Place the file where your http web server see it. e.g: /var/www

Open the file in a web browser. e.g: http://localhost/primeNumberCalculator.php

<html>
<body>

<h2>PHP Prime number calculator</h2>
<form name="input" action="primeNumberCalculator.php" method="get">
How many primes?: <input type="text" name="count" />
<input type="submit" value="Submit" />
</form>
<?php

// How many prime numbers are we going to calculate:
$count=$_GET["count"];
if ($count == "") {
   $count = 10;  // Default value
}

// We show the first prime number:
$prime_array=array("2");
echo $prime_array[0];
echo " ";

$total=1; // prime number array length.
$number = 3; // current number we are going to test for primality.

$i=1; // We start with 1 because first prime is already printed.
while ( $i<$count ) {
   $index=0;
   $is_prime="true";
   $max = floor(sqrt($number));
   $n = $prime_array[$index];
   while(($n <= $max) && ($is_prime == "true")) {
      if (($number % $n) == 0) {
         $is_prime="false";
      }
      $index++;
      $n = $prime_array[$index];
   }
   if ($is_prime=="true") {
      echo " " . $number;
      $prime_array[$total] = $number;
      $total++;
      $i++;
   }

   $number += 2;
}

?>

</body>
</html>

Calculate a PRIME NUMBER list using JAVA

2011-01-12T21:43:00.005+01:00

This article shows how to write, compile, build and execute a program that calculates a list containing the first prime numbers using Java language.

We are going to create a source code file named CalculatePrimeNumbers.java
Then we copy/paste next programm in that file.

NOTE: Name is important, because in Java language file name has to match the class it contains.

import java.util.ArrayList;

/**
 * Description of CalculatePrimeNumbers class.
 */
public class CalculatePrimeNumbers {

    // By default it shows 50 first prime numbers.
    private static final int MAX_PRIMES = 50;


    /**
     * @param args the command line arguments
     * This function accepts zero or one arguments.
     * When called with no arguments it shows 50 first prime numbers.
     * If we specify a number, it shows that a prime number array with that specified length.
     */
    public static void main(String[] args) {
        int top;

 // Parse command line arguments.
        switch(args.length){
            case 0:
                top = MAX_PRIMES;
                break;
            case 1:
                top = Integer.parseInt(args[0]);
                break;
            default:
                System.err.println("ERROR: TOO MANY ARGUMENTS.");
                return;
        }
        System.out.println("We are going to calculate " + top + " first prime numbers.");


 ArrayList<long> primes = new ArrayList<long>();
        primes.add(2L); // 2 is the first prime number we get.
 long index = 3; // Calculations start for number 3.

        System.out.println("Prime number list:");
        System.out.print(2 + " ");
        while (primes.size() < top) {
            boolean isPrime = true;

     for(long n:primes) {
                if ((index % n) == 0) {
                    isPrime = false;
                    break;
                }
            } // End for.

            if (isPrime) {
                // index stores a prime number.
                primes.add(index);
                System.out.print(index + " ");
            }

            index++;
        } // End while.
       
    } // End main.

}

Java is a programming language that is compiled into bytecodes.
Read more »

Beginning with Qt: Introduction, Installing Qt Framework, Qt Hello world

2010-08-25T19:17:00.003+02:00

INTRODUCTION TO Qt

Qt is a complete development environment widely used to create GUI applications.

This cross-platform tool is also able to create non gui apps.

Qt is used in the KDE desktop environment, and in other projects like virtualbox.

Qt development environment provides: (version numbers when this article was written)

Qt libraries (version 4.6.3)
Qt Creator IDE (version 2.0.0)
Qt development tools

Qt is available under LGPL and GPL free software licenses. Nokia also provides the Qt commercial license to develop proprietary software.

Qt DEVELOPMENT TOOLS

Qt environment provides us with some development tools. e.g:

qmake
qmake tool helps us creating and managing .pro project files, and from them it creates Makefile files needed to build our projects.
qmake Manual
qmake Tutorial

Qt assistant
Qt assistant tool shows all available Qt help. It is a help browsing system.
Qt Assistant Manual
Read more »

Creating a TRIVIAL DEBIAN REPOSITORY

2010-06-26T20:20:00.008+02:00

This howto shows the way to create a trivial debian repository. Just a simple collection of deb package files.

There are two debian repository types: automatic and trivial.

Automatic repos are more complex. We are going to deal with trivial ones.

A trivial repository is composed of a root directory and one or more subdirectories.
No database server is needed.

This trivial repository is good enough to host a few packages, e.g creating a repo with your /var/cache/apt/archives deb packages and burn a cd or store them in a removible drive.

Trivial repos do not follow the standard debian repo directory structure, so we will have to specify the exact path in sources.list file.

CREATING MY TRIVIAL REPO STRUCTURE:

Our repo will consist of MyRepo root directory with binary subdirectory.

$mkdir -p /path/to/MyRepo
$cd /path/to/MyRepo
$mkdir binary

We place there the deb packages our repo will provide.
I.e: we copy packages from the apt cache:
$rsync -vP /var/cache/apt/archives/*.deb /path/to/MyRepo/binary
$cd .. # we move to repo root directory.

CREATE PACKAGES CONFIGURATION FILE

Now we create Packages configuration file and place it in binary directory:
dpkg-scanpackages -m binary /dev/null > binary/Packages # -m option indicates it should include all found packages not only the latest version one.

Packages file shows a package name list with dependency data, checksums, etc...

We can compress it with gzip if it occupies a lot of size.

cd binary; gzip Packages # Packages.gz file will be created.

UPDATE YOUR sources.list FILE:

Add this line in /etc/apt/sources.list file (trailing slash is necessary for trivial repos)
deb file:///path/to/MyRepo binary/

If there would be the root directory only and no subdir: deb file:///path/to/MyRepo ./

UPDATE THE APT DATA BASE

#aptitude update or #apt-get update

Now we can install whatever package from our repo.

CAVEATS
Trivial repositories do not deal with architectures

They do not use a pool directory.

If we want to add new packages we have to repeat the whole process and generate a new Packages file.

REFERENCE:

http://wiki.debian.org/HowToSetupADebianRepository

http://www.debian.org/doc/manuals/repository-howto/repository-howto.en.html

$man dpkg-scanpackages

Howto BUILD the LINUX KERNEL for the ANDROID EMULATOR (Eclair version)

2010-05-02T01:06:00.005+02:00

DOWNLOAD THE KERNEL SOURCE CODE

First we download the kernel source code from http://android.git.kernel.org

Within that page there are kernels for other platforms too. We choose to download kernel/common project from there.

$git clone git://android.git.kernel.org/kernel/common

We check which branch we have downloaded:
$git branch
it shows * android-2.6.27, not the one we are searching for:

To list all remote available branches:
$git branch -r

  origin/HEAD -> origin/android-2.6.27
  origin/android-2.6.25
  origin/android-2.6.27
  origin/android-2.6.29
  origin/android-2.6.32
  origin/android-goldfish-2.6.27
  origin/android-goldfish-2.6.29

What does goldfish mean? (from android-kernel mail list)
Goldfish is the kernel hacked branch that supports the qemu based arm emulator for android, so it is the one we need.

Download GOLDFISH kernel version
$git checkout --track -b android-goldfish-2.6.29 origin/android-goldfish-2.6.29
$git branch

    android-2.6.27
  * android-goldfish-2.6.29

RUNNING THE EMULATOR

Within this link we will find how to get the android emulator, and launch it.
Building Android in Debian Sid

Showing the kernel version running in the emulator
$adb shell
#cat /proc/version

Linux version 2.6.29-00261-g0097074 (digit@digit.mtv.corp.google.com) (gcc version 4.4.0 (GCC) ) #14 Tue Feb 2 15:49:02 PST 2010

OBTAINING KERNEL CONFIGURATION

We are going to obtain the kernel configuration .config file from within our running emulator.

$cd common # we enter in the kernel source directory.
$adb pull /proc/config.gz . # get compressed .config file from the emulator.

$gunzip config.gz # uncompress it.
$cp config .config # rename it into .config

Now you can edit .config file the way it suits you the most.

BUILDING AND COMPILING THE KERNEL

CROSS_COMPILE environment variable stores the path to the arm cross compiling toolchain. I use the one which comes with android source code.

$ARCH=arm CROSS_COMPILE=/path/to/mydroid/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin/arm-eabi- make

Executing make will build the kernel.

Last lines will show:

  Kernel: arch/arm/boot/Image is ready
  Kernel: arch/arm/boot/zImage is ready

So we have obtained Image and zImage kernel binary files.

RUN THE EMULATOR USING THE NEW COMPILED KERNEL IMAGE

We need -kernel option:
$emulator -kernel /path/to/common/arch/arm/boot/zImage -show-kernel -verbose

We can check now the kernel version:
$adb shell
# cat /proc/version

Linux version 2.6.29-00262-gb0d93fb (user@myPC) (gcc version 4.4.0 (GCC) ) #1 Sun May 2 14:27:31 CEST 2010

If we do not specify kernel option it usually uses the prebuilt one:
$emulator -show-kernel -verbose

emulator: argv[01] = "-kernel"
emulator: argv[02] = "/path/to/mydroid/prebuilt/android-arm/kernel/kernel-qemu"

ACTIVATING MODULE LOADING SUPPORT IN THE KERNEL

Module loading support is previously disabled in the kernel, if we want to load modules in the kernel we have to enable it:

edit .config file and set:
CONFIG_MODULES=y

$ ARCH=arm CROSS_COMPILE=/path/to/mydroid/prebuilt/linux-x86/toolchain/arm-eabi-4.4.0/bin/arm-eabi- make

I am asked about some options when executing make. I ask yes for module related options.

After compiling I see several modules have been built.

MODPOST 6 modules
  CC      drivers/video/fb_sys_fops.mod.o
  LD [M]  drivers/video/fb_sys_fops.ko
  CC      drivers/video/syscopyarea.mod.o
  LD [M]  drivers/video/syscopyarea.ko
  CC      drivers/video/sysfillrect.mod.o
  LD [M]  drivers/video/sysfillrect.ko
  CC      drivers/video/sysimgblt.mod.o
  LD [M]  drivers/video/sysimgblt.ko
  CC      drivers/video/vfb.mod.o
  LD [M]  drivers/video/vfb.ko

We can upload the modules in the emulator and install them:
$adb push drivers/video/fb_sys_fops.ko /data
$adb shell
#insmod /data/fb_sys_fops.ko

REFERENCE

http://www.cianer.com/androidg1/28-building-android-kernel-images

Building Android in Debian Sid

2010-04-25T23:05:00.008+02:00

We are going to build and test Android in Debian Sid on x86 32 bits architecture.

As a requirement we need JDK 5.0, update 12 or higher. Java 6 is not supported, because of incompatibilities with @Override.

Debian Sid provides all packages we need except this one. We could install from source but instead we are going to install JDK 5.0 from Debian Stable (Lenny) repositories:

ADD DEBIAN STABLE (LENNY) REPOSITORIES
#echo "deb http://ftp.debian.org/debian/ stable main contrib non-free" >> /etc/apt/sources.list

#aptitude update

sun-java5-jdk package will now become available.

INSTALL ALL PACKAGES WE NEED:

#aptitude install git-core gnupg sun-java5-jdk flex bison gperf libsdl-dev libesd0-dev libwxgtk2.6-dev build-essential zip curl libncurses5-dev zlib1g-dev

SELECT THE RIGHT JAVA VERSION:
$file /etc/alternatives/java* # To know which alternative files we have to update.
#update-alternatives --config java
#update-alternatives --config java_vm
#update-alternatives --config javaws

We also install valgrind, a tool that will help you find memory leaks, stack corruption, array bounds overflows, etc.
#aptitude install valgrind

Android projects are stored in Git repositories. Also they have developed a tool called REPO to facilitate working with git repositories.

INSTALLING REPO

You can install repo tool any place in your path. We choose a bin directory in our home folder:

$cd ~
$mkdir bin
$export PATH=$PATH:~/bin
$curl https://android.git.kernel.org/repo >~/bin/repo
$chmod a+x ~/bin/repo

DOWNLOADING ANDROID SOURCE CODE:

Create an empty directory to hold your working files:
$mkdir mydroid
$cd mydroid

# Run repo init to bring down the latest version of Android with all its most recent bug fixes. You must specify a URL for the manifest:
$repo init -u git://android.git.kernel.org/platform/manifest.git

NOTE: using -b option we can choose which android version to install:
$repo init -u git://android.git.kernel.org/platform/manifest.git -b eclair

To pull down files to your working directory from the repositories as specified in the default manifest, run
$repo sync

NOTE: mydroid directory size grows up to 3.6G.

BUILDING ANDROID

Simply on top of your android directory execute make command:
$cd mydroid
$make

After some time it will finish.

We get the installed file list in this file:
out/target/product/generic/installed-files.txt

Also some images are created in the same directory: (system.img userdata.img ramdisk.img)

mydroid$ ls out/target/product/generic/
android-info.txt  data                 obj                       ramdisk.img  symbols  system.img
clean_steps.mk    installed-files.txt  previous_build_config.mk  root         system   userdata.img

We have built android source code but now we want to test it:

ANDROID EMULATOR

We will run the Android Emulator, which comes within the Android SDK
http://developer.android.com/guide/developing/tools/emulator.html

Download Android SDK
http://developer.android.com/sdk/index.html

Install Android SDK
http://developer.android.com/sdk/installing.html

We untar the sdk and add tools directory into the PATH variable:
$tar xvzf android-sdk_r05-linux_86.tgz
$export PATH=$PATH:~/android-sdk-linux_86/tools

We are not going to create an android virtual device, but instead we will use an environment variable to indicate where our images are:

RUNNING ANDROID EMULATOR

$emulator -help # Shows some help.

$export ANDROID_PRODUCT_OUT=/path/to/mydroid/out/target/product/generic/ # Env variable showing where our images are.

We create a SD image to simulate a SD card:
$cd mydroid/out/target/product/generic/
$mksdcard -l SD 100M sdcard.img

Run the emulator program:
$emulator -verbose

if we want more debug information:
$emulator -show-kernel -verbose

CONNECTING TO THE EMULATOR USING ADB (ANDROID DEBUG BRIDGE) TOOL

adb tool comes within Android SDK.

In a console we execute:
$adb devices

It will show available devices in your system:

List of devices attached
emulator-5554   device

We can now connect to the device:
$adb shell

REFERENCE:
http://source.android.com/download

Connect to Internet using a K530i phone in Debian GNU/Linux via Bluetooth

2010-03-28T14:07:00.003+02:00

Within this post we are going to explain how to connect to internet using a Sony Ericsson K530i mobile phone via bluetooth, in a Debian Sid system.

This previous post explains same process via usb cable:
Connecting to Internet using a Sony Ericsson K530i mobile phone in Ubuntu (Linux) via USB cable.

First step consists on configuring bluetooth settings in our phone.

CONFIGURING OUR K530i PHONE

Activate bluetooth in the phone:
Settings -> Connectivity -> Bluetooth -> Turn on

Set a name for your phone:
Settings -> Connectivity -> Bluetooth -> Phone name
We select a name for our phone, e.g: my_K530i

Make your phone visible to other bluetooth devices:
Settings -> Connectivity -> Bluetooth -> Visibility -> Show phone

INSTALLING BLUETOOTH SOFTWARE

We are going to install the bluetooth sofware we need:
#aptitude install bluez

Bluez package provides the tools and system deaemons we need to deal with bluetooth devices.

Right now I am using bluez version 4.60-1

BlueZ is the official Linux Bluetooth protocol stack.

CONFIGURING A BLUETOOTH CONNECTION

Now we will set a connection between our computer and the k530i phone.

List all bluetooth devices in our system:
$ hciconfig
hci0: Type: USB
BD Address: 00:1F:3A:79:CB:E0 ACL MTU: 1017:8 SCO MTU: 64:8
UP RUNNING PSCAN
RX bytes:1059 acl:0 sco:0 events:34 errors:0
TX bytes:369 acl:0 sco:0 commands:28 errors:0

So we have a hci0 device up and running in our system.

We scan for external bluetooth devices:
$ hcitool scan
Scanning ...
00:1E:45:5A:FE:2E my_K530i

Scan command shows our phone name and mac.

We ping the phone to test it is alive:
$l2ping 00:1E:45:5A:FE:2E

Show all available bluetooth services offered by our phone:
$sdptool browse 00:1E:45:5A:FE:2E

We are interested in Dial-up Networking service (DUN):
Shows only Dial-up Networking service:
$sdptool search --bdaddr 00:1E:45:5A:FE:2E DUN

We find which channel DUN service is associated to and will use it in rfcomm.conf settings.

EDITING rfcomm.conf CONFIGURATION FILE

We edit /etc/bluetooth/rfcomm.conf file:

#
# RFCOMM configuration file.
#

rfcomm0 {
 # Automatically bind the device at startup
 bind yes;

 # Bluetooth address of the device
 device 00:1E:45:5A:FE:2E;

 # RFCOMM channel for the connection
 channel 1;   # In my phone DUN device is associated to channel 1.

 # Description of the connection
 comment "K530i link";
}

MAKE EFFECTIVE OUR CHANGES
#/etc/init.d/bluetooth restart

If everything has gone fine, a /dev/rfcomm0 device will appear.

NOTE: If we would want to manually set up /dev/rfcomm0 device these are the commands you need
(You actually do not need them if you exec: #/etc/init.d/bluetooth restart)

#mknod -m 660 /dev/rfcomm0 c 216 0
#chown root:dialout /dev/rfcomm0
#rfcomm bind 0

PAIRING OUR BLUETOOTH DEVICES

bluetooth-agent program commes within bluez package. It will help us to pair our bluetooth devices. We execute it in a console. e.g:

$bluetooth-agent 3333
# We set 3333 as the needed code to pair the devices. Select a code that suits you.

DIALING TO OUR 3G PROVIDER

We will use wvdial and pppd programs to configure and establish a ppp connection.
#aptitude install wvdial

Edit ~/.wvdialrc file:

Change this in your .wvdialrc file to suit your phone operator company:


[Dialer Masmovil]
Phone = *99***1#
Username = "masmovil"
Password = "masmovil"
Modem = /dev/rfcomm0
Baud = 460800
Stupid Mode = 1
Init1 = ATZ
Init3 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ISDN = 0
Modem Type = Analog Modem
Init5 =AT+CGDCONT=1,"IP","internetmas";

Execute wvdial to establish the connection:
$wvdial Masmovil

First time the phone will ask us about "an unknown device trying to connect to the phone". We grant permission.
It will then ask us about accessing the phone services: We answer yes.
It asks for the pin: we enter 3333 (same as the bluetooth agent)

And connection will establish!!

When connected we will be able to see the connection:
$ hcitool con
Connections:
< ACL 00:1E:45:5A:FE:2E handle 11 state 1 lm MASTER AUTH ENCRYPT

REFERENCE:
http://web.inter.nl.net/users/hanscees/bluezhowto.html
http://ornellas.apanela.com/dokuwiki/pub:linux_bluetooth_gprs

Howto Create a GENTOO Distro CHROOT ENVIRONMENT

2010-02-28T19:14:00.022+01:00

This article describes how to build a chroot environment for Gentoo distribution.

NOTE: Debian GNU/Linux will be our host system, but these steps should also work for most other Linux based distributions (e.g: Ubuntu).

DOWNLOAD A SMALL MINIMUM GENTOO SYSTEM

First we are going to download a minimal Gentoo system, called STAGE3.

We choose our architecture, in my case x86, and i686 specifically.
http://mirrors.kernel.org/gentoo/releases/x86/autobuilds/current-stage3/
$wget http://mirrors.kernel.org/gentoo/releases/x86/autobuilds/current-stage3/stage3-i686-*.tar.bz2

There is a list of mirrors here: http://www.gentoo.org/main/en/mirrors.xml

We could download directly from gentoo page too:
$wget ftp://distfiles.gentoo.org/pub/gentoo/releases/x86/current-stage3/stage3-i686-*.tar.bz2

BUILDING OUR GENTOO DIRECTORY

We create a directory where we will place Gentoo files:
$mkdir gentoo_chroot
and uncompress there the stage3 archive.
#tar xvjf stage3-i686-20100216.tar.bz2 -C gentoo_chroot/

Copy resolv.conf file to resolve names:
#cp -L /etc/resolv.conf gentoo_chroot/etc/resolv.conf
We will be able to resolve addresses.

Copy /etc/host file:
#cp /etc/hosts gentoo_chroot/etc/
or we could create a new one:
e.g: #echo "127.0.0.1 mybox.at.myplace mybox localhost" > gentoo_chroot/etc/hosts

I like using same hostname as the host one because if we change it in chroot, it also changes in the host.

When we will enter in the chroot jail we will be able to exec:
#hostname -f # shows mybox.at.myplace.
#ping mybox.at.myplace

MOUNTING NEEDED DIRECTORIES

We use bind option to duplicate some host directories in the chroot filesystem:

#mount --bind /dev gentoo_chroot/dev
#mount --bind /proc gentoo_chroot/proc
#mount --bind /sys gentoo_chroot/sys
#mount --bind /dev/pts gentoo_chroot/dev/pts # Needed for agetty login and screen command.
#mount --bind /tmp gentoo_chroot/tmp # If we want share X windows between host and guest.

ENTERING THE CHROOT ENVIRONMENT

#chroot gentoo_chroot /bin/bash
We are in the gentoo chroot envirionment!!
Unless told, every command from now on is executed within the chroot env.

To update and configure some environment variables:
#env-update
#source /etc/profile # To configure our current shell environment.

CUSTOMIZING YOUR PROMPT

We can also customize our prompt to show we are in the chroot jail.
#export PS1="(chroot) $PS1"

If we want to customize every login prompt we have to change /etc/profile.
#echo "export PS1=\"(chroot) \$PS1\"" >> /etc/profile
For non login shells you have to edit .bashrc file.

CREATE /etc/mtab FILE

#cp /proc/mounts gentoo_chroot/etc/mtab

Some mtab file lines are useless so we edit them:
#nano -w /etc/mtab

We leave something like that:

udev /dev tmpfs rw,relatime,size=10240k,mode=755 0 0
none /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
none /proc proc rw,nosuid,nodev,noexec,relatime 0 0
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000 0 0

Now we are able to exec mount and df commands.

SETTING THE TIMEZONE

#ls /usr/share/zoneinfo # Shows all available timezones.
#cp /usr/share/zoneinfo/Europe/Madrid /etc/localtime # I use Madrid timezone.

CONFIGURE LOCALES

$cd /etc
#nano -w locale.gen
I add: es_ES.UTF-8 UTF-8 # Spanish specific locales, choose the ones which suit you.
#locale-gen # we generate locales.
We change locale:
#export LANG=es_ES.UTF-8
# locale

CHANGE ROOT PASSWORD

#passwd root

edit /etc/securetty file
#nano -w /etc/securetty
Add there all tty where you want to login as root from. e.g: add pts/5 if you want to login from /dev/pts/5 tty.
Exec $echo $(tty) in your host to show which tty you are in.

ADDING A NEW USER

We are going to create an user called new_user:
#useradd -m new_user # -m option to create home directory.
#passwd new_user # change the user password.
#su new_user # become that user.

LOGIN IN ANOTHER WAY

Entering the chroot environment using the already told way mixes host and guest env variables.

A better way is using agetty command, execute in the host system:
#chroot gentoo_chroot/ /sbin/agetty $(tty) 38400

We can login as root or as the new user we have just created.

NOTE: The standard user wont be able to gain root privileges using su command unless he pertains to wheel group, so:

#usermod -a -G wheel new_user
#su new_user
$su root
If not we will get "su: permission denied error".

Now user new_user can exec su command and become root.

DOWNLOAD PORTAGE SNAPSHOT

Portage is the Gentoo package management system.

We are going to install portage subsystem because we want to install more gentoo available packages.

#cd /usr # Portage is placed in /usr directory.
#wget http://distfiles.gentoo.org/snapshots/portage-latest.tar.bz2 # (35 MBytes)
or we could choose download it from a mirror: http://www.gentoo.org/main/en/mirrors.xml

Uncompress it:
#tar xvjf portage-latest.tar.bz2

EMERGE TOOL

Emerge is the command line tool which allow us to search, install, update, remove, etc gentoo packages.

Install less pager:
$emerge --search less
We see: sys-apps/less
#emerge less # we install less pager.
less tool is compiled and installed.

Install screen terminal manager:
$emerge --color y --search screen | less
#emerge -v screen

Now we are going to install a text web client:
Searching into categories. e.g: www-client
$emerge --search @www-client --color y | less
#emerge -v links
$links http://linuxclues.blogspot.com

My favourite text editor:
$emerge --color y --search emacs | less
$emerge --pretend emacs # To see what is going to happen without installing anything.
#emerge -v emacs
#tail -f /var/log/emerge-fetch.log # to see package downloading status.

SHARING X BETWEEN HOST AND CHROOT GUEST

#emerge -v xclock # we will use xclock tool to test the X system.

We need to obtain permissions and store it in .Xauthority file.
In the host machine exec:
$xauth list
we obtain something like:

mybox/unix:0  MIT-MAGIC-COOKIE-1  5e20455a59909d2f911d73b8d7d8cba5

As I am using unix socket X display :0, I copy that line.

In the chroot env.
#emerge xauth
#xauth add mybox/unix:0 MIT-MAGIC-COOKIE-1 5e20455a59909d2f911d73b8d7d8cba5
#DISPLAY=:0.0 xclock # we can exec X apps as root.
$xauth add mybox/unix:0 MIT-MAGIC-COOKIE-1 5e20455a59909d2f911d73b8d7d8cba5
$DISPLAY=:0.0 xclock # we can exec X apps as a standard user.

INSTALLING MPLAYER TO TEST VIDEO AND SOUND

#emerge -v mplayer

After installation it runs correctly as root, but not as a standard user. We need to give him audio privileges.

As I use alsa sound drivers:
$ls -l /dev/snd
I see in files owned by group 29 (legacy from host machine)
We edit /etc/group file and change audio group gid into 29.
#nano -w /etc/group
audio::29:

Add the standard user to audio group:
#usermod -a -G audio new_user
#su new_user
$mplayer -vo xv -framedrop foo.avi

EXITING THE CHROOT JAIL
Simply type:
$exit

UMOUNT

After exit we unmount binded directories:
#umount gentoo_chroot/dev/pts
#umount gentoo_chroot/dev
#umount gentoo_chroot/proc
#umount gentoo_chroot/sys
#umount gentoo_chroot/tmp

NOTE: when unmounting if it complains about a bind mount busy. You can use mount -M to move it to another place instead.
It is an ugly workaround, I now. :-D

REFERENCE:

Gentoo Quick Install Guide
Portage (Wikipedia)

$man emerge

Gentoo Documentation

HowTo Show Network Speed in Emacs Mode Line

2010-01-07T16:40:00.004+01:00

Copy this file as network-speed.el. Place it where emacs can find it (see load-path variable).

Configure your .emacs file:


;; network-speed configuration:
(add-to-list 'load-path "/path/to/network-speed.el")
(require 'network-speed)
(network-speed-start)

Reload your .emacs file: M-x load-file RET /path/to/.emacs

To stop showing network speed in mode line execute:
M-x network-speed-stop


;;; network-speed.el --- display network speed information  -*- coding: mule-utf-8 -*-

;; Copyright (C) 2009 Vicente Hernando Ara

;; Author: Vicente Hernando Ara 

;; Created: 1 Jan 2010

;; Keywords: hardware

;; This file is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.



;;; Commentary:

;; network-speed.el package displays network speed in emacs mode line for the interfaces the user selects.


;; There are several configurable options:

;;   network-speed-update_interval: time interval after which speed is calculated.

;;   network-speed-interface-list: list containing all network interfaces we want to show data about.

;;   network-speed-precision: every floating point number will show this number of figures after decimal point.

;;   network-speed-format-string: customizable string to be shown in the mode line.
;;   There are several scape strings which will be sustituted by data.
;;     %NI == network interface
;;     %RX == received bytes speed 
;;     %TX == transmitted bytes speed
;;     %AX == received + transmitted bytes speed
;;     %RB == total received bytes
;;     %TB == total transmitted bytes
;;     %AB == total received plus transmitted bytes
;;     %%% == % character"

;; After this file is loaded, it is necessary to call `network-speed-start' function.
;; To stop network-speed working  you need to call `network-speed-stop' function.

;;      
;; A lot of ideas were taken from `battery.el.gz' file.


;;; NETWORK-SPEED CONFIGURATION
;;
;; Add something like this in your .emacs file:
;;
;; ;; Custom variables:
;;  '(network-speed-update-interval 2)   ; Shows network speed every 2 seconds.
;;  '(network-speed-interface-list (list "ppp0" "eth0"))  ; Network interfaces to be shown in mode line.
;;  '(network-speed-precision 1)  ; Number of figures after decimal point.
;;  '(network-speed-format-string " [%NI total: %AX] ") ; String format.
;;
;; ;; network-speed configuration:
;; (add-to-list 'load-path "/path/to/network-speed.el")
;; (require 'network-speed)
;; (network-speed-start) ; 
;;
;; ;; to stop network-speed, call "network-speed-stop" interactive function.
;; ;; (network-speed-stop)


;;; Code:

;;; CUSTOM VARIABLES:

;; Network interface list to be shown in mode line.  
;;   E.g: `(list "ppp0" "eth0" "ppp1")'
(defcustom network-speed-interface-list (list "eth0") "Network interface list to be shown in mode line."
  :type '(repeat string) )

(defcustom network-speed-update-interval 1 "Network speed is calculated every network-speed-update-interval seconds."
  :type 'number )

(defcustom network-speed-precision 2 "Number of digits after point in numbers shown in mode line."
  :type 'integer )

;; String used to build the output string shown in emacs mode line.
(defcustom network-speed-format-string " [%NI rx:%RX tx:%TX] " "Format string. 
%NI == network interface
%RX == received bytes speed 
%TX == transmitted bytes speed
%AX == received + transmitted bytes speed
%RB == total received bytes
%TB == total transmitted bytes
%AB == total received plus transmitted bytes
%%% == % character"
  :type 'string
)


(defvar network-speed-update-timer nil)

;; List that contains vectors like this: [ network-interface-string received-bytes transmitted-bytes rx-speed tx-speed ]
;; This variable is only for internal use.
(defvar network-speed-data-list nil) 

;; We will parse /proc/net/dev file using the returned regexp.
(defun network-speed-get-regex (network-interface)
  "Returns the right regular expression needed to find received and transmitted bytes for NETWORK-INTERFACE."
  (concat "^\\( *" network-interface ":[ ]*\\)"
   "\\([0-9]+\\)" ; received bytes.
   "\\( +[0-9]+\\)\\{7\\} +"
   "\\([0-9]+\\)"))  ; transmitted bytes.


(defun network-speed-get-rx-tx-bytes ()
  "Gets received and transmitted bytes for every required network interface and calculates received and transmitted speeds.
Received and transmitted bytes are read from `/proc/net/dev' file"
  (mapc
   (lambda (network-speed-data)
     (with-temp-buffer
       (ignore-errors (insert-file-contents "/proc/net/dev")) 
       (cond ((re-search-forward (network-speed-get-regex (aref network-speed-data 0)) (point-max) t)
       (let ((old-received-bytes (aref network-speed-data 1)) ; get old received bytes.
      (old-transmitted-bytes (aref network-speed-data 2)) ; get old transmitted bytes.
      (received-bytes (string-to-number (match-string 2))) ; get updated received bytes.
      (transmitted-bytes (string-to-number (match-string 4)))) ; get updated transmitted bytes.
  
  ;; Save received and transmitted bytes.
  (aset network-speed-data 1 received-bytes) 
  (aset network-speed-data 2 transmitted-bytes)
  
  ;; Save received and transmitted speed.
  (aset network-speed-data 3 (/ (float (- received-bytes old-received-bytes)) network-speed-update-interval))
  (aset network-speed-data 4 (/ (float (- transmitted-bytes old-transmitted-bytes)) network-speed-update-interval))))
      (t 
       (aset network-speed-data 3 -1 ) ; There is no network interface available.
       (aset network-speed-data 4 -1 ))))) ; There is no network interface available.
   
   network-speed-data-list))


(defun network-speed-add-units (speed)
  "Returns speed in adequate units e.g: B/s, KB/s or MB/s."
  (cond 
   ((< speed 0) (format "*")) ; Network interface not available right now.
   ((< speed 1000) (format "%d B/s" speed))  
   ((< speed 1000000) (format (concat "%." (number-to-string network-speed-precision) "f KB/s") (/ speed 1000)))
   (t (format (concat "%." (number-to-string network-speed-precision) "f MB/s") (/ speed 1000000)))))


(defun network-speed-parse-format (vector-data)
  "Substitute %XX sequences in network-speed-format-string."
  (replace-regexp-in-string 
;;;   "%NI\\|%RX\\|%TX\\|%AX\\|%RB\\|%TB\\|%%%"
   "%\\(NI\\|RX\\|TX\\|AX\\|RB\\|TB\\|AB\\|%%\\)"
   (lambda (str)
     (cond 
      ((equal str "%NI") (aref vector-data 0))  ; network interface.
      ((equal str "%RX") (network-speed-add-units (aref vector-data 3)))  ; received bytes speed.
      ((equal str "%TX") (network-speed-add-units (aref vector-data 4)))  ; transmitted bytes speed.
      ((equal str "%AX") (network-speed-add-units (+ (aref vector-data 3) (aref vector-data 4)))) ; received + transmitted speed.
      ((equal str "%RB") (format "%d" (aref vector-data 1))) ; received bytes.
      ((equal str "%TB") (format "%d" (aref vector-data 2))) ; transmitted bytes.
      ((equal str "%AB") (format "%d" (+ (aref vector-data 1) (aref vector-data 2)))) ; received + transmitted bytes.
      ((equal str "%%%") "%") ; % character.
      )
     )
   network-speed-format-string t t)
)


(defun network-speed-update-handler()
  "This function is called every `network-speed-update-interval' seconds to calculate data and show network speed in modeline."
  (network-speed-get-rx-tx-bytes)
  
  (setq network-speed-mode-line-string "")
  (mapc 
   (lambda (network-speed-data)
     (setq network-speed-mode-line-string 
    (concat network-speed-mode-line-string 
     (network-speed-parse-format network-speed-data))))  ; Obtains the string we will show.
   network-speed-data-list)

  (force-mode-line-update)
  (sit-for 0))


(defun network-speed-start ()
  "Shows network speed in mode line. 
This function initializes all needed data. 
Speed is not shown inmediately but after `network-speed-update-interval' seconds when first correct value is calculated."
  (interactive)

  ;; Adding network-speed-mode-line-string to global mode line.
  (setq network-speed-mode-line-string "")
  (add-to-list 'global-mode-string 'network-speed-mode-line-string t)

  ;; Initialize all needed vectors in `network-speed-data-list'.
  (setq network-speed-data-list ())
  (mapc 
   (lambda (x)
     (add-to-list 'network-speed-data-list (vector x 0 0 0 0) t))  ; Initialices and element of network-speed-data list.
   network-speed-interface-list)

  ;; Calculate speeds.
  (network-speed-get-rx-tx-bytes)

  ;; Create network-speed-update-timer. 
  (and network-speed-update-timer (cancel-timer network-speed-update-timer))
  ;; This does not inmediately show speeds but it waits `network-speed-update-interval' seconds to start showing it.
  (setq network-speed-update-timer (run-at-time network-speed-update-interval network-speed-update-interval 'network-speed-update-handler)))


(defun network-speed-stop ()
  "Stops displaying network speed in mode line."
  (interactive)
  ;; Delete the text from global mode line.
  (setq global-mode-string (delq 'network-speed-mode-line-string global-mode-string))

  ;; Cancel timer.
  (and network-speed-update-timer (cancel-timer network-speed-update-timer)))


(provide 'network-speed)

;;; filename ends here

MANIFESTO on the RIGHTS of INTERNET USERS

2009-12-07T09:33:00.002+01:00

1 . Copyright should not be placed above citizens' fundamental rights to privacy, security, presumption of innocence, effective judicial protection and freedom of expression.

2 . Suspension of fundamental rights is and must remain an exclusive competence of judges. This blueprint, contrary to the provisions of Article 20.5 of the Spanish Constitution, places in the hands of the executive the power to keep Spanish citizens from accessing certain websites.

3 . The proposed laws would create legal uncertainty across Spanish IT companies, damaging one of the few areas of development and future of our economy, hindering the creation of startups, introducing barriers to competition and slowing down its international projection.

4 . The proposed laws threaten creativity and hinder cultural development. The Internet and new technologies have democratized the creation and publication of all types of content, which no longer depends on an old small industry but on multiple and different sources.

5 . Authors, like all workers, are entitled to live out of their creative ideas, business models and activities linked to their creations. Trying to hold an obsolete industry with legislative changes is neither fair nor realistic. If their business model was based on controlling copies of any creation and this is not possible any more on the Internet, they should look for a new business model.

6 . We believe that cultural industries need modern, effective, credible and affordable alternatives to survive. They also need to adapt to new social practices.

7 . The Internet should be free and not have any interference from groups that seek to perpetuate obsolete business models and stop the free flow of human knowledge.

8 . We ask the Government to guarantee net neutrality in Spain, as it will act as a framework in which a sustainable economy may develop.

9 . We propose a real reform of intellectual property rights in order to ensure a society of knowledge, promote the public domain and limit abuses from copyright organizations.

10 . In a democracy, laws and their amendments should only be adopted after a timely public debate and consultation with all involved parties. Legislative changes affecting fundamental rights can only be made in a Constitutional law.

REFERENCE

Facebook group supporting the manifesto

Manifesto Signing Petition

Dangerous Anti-Sharing Law in Spain | La Quadrature du net

Install and Configure quickly a DHCP Server

2009-11-21T19:32:00.003+01:00

NOTE: These commands have been tested in Debian version unstable.

DHCP stands for Dynamick Host Configuration Protocol. This protocol allows to automatically obtain an IP address and set the network configuration.

We install a DHCP server:
#aptitude install dhcp3-server

Next step is configuring the DHCP server:
We have to set correcty the /etc/dhcp3/dhcpd.conf file.

There is a configuration file example at:
/usr/share/doc/dhcp3-server/examples/dhcpd.conf

e.g: I added these lines to my /etc/dhcp3/dhcpd.conf


subnet 192.168.1.0 netmask 255.255.255.252 {
       range 192.168.1.2 192.168.1.3;
       option routers 192.168.1.1;
       option domain-name-servers 212.73.32.3, 212.73.32.67;
}

subnet and netmask indicate the network addresses of our network:
e.g: subnet 192.168.1.0 netmask 255.255.255.252 match 192.168.1.0, 192.168.1.1, 192.168.1.2 and 192.168.1.3 IP addresses.

range means which addresses can be returned by our dhcp server, here, it can return 192.168.1.2 and 192.168.1.3

routers indicates the gateway

domain-name-servers shows all dns addresses separated by commas.

Once we have correctly set dhcpd.conf file we restart the dhcp daemon:
#/etc/init.d/dhcp3-server restart

If everything has gone fine, we will execute in a client computer:
$sudo dhclient eth0

and the dhcp server will associate an IP adress to eth0 interface.

NOTE: dhcp3-client package provides dhclient command.
#aptitude install dhcp3-client

Shell Script that shows Network Speed

2009-11-01T22:29:00.005+01:00

The following shell script shows current download and upload speeds for the network interface you choose.

Copy the shell script in a file named, i.e: net_speed.sh

Then after setting execution permissions:
$chmod a+x net_speed.sh

You can run the shell script passing as the first argument the network interface you want to monitor:
./net_speed.sh eth0

You will get a line like that:
ppp0 DOWN:15 KB/s UP:880 B/s

This script works parsing /proc/net/dev file and calculating the difference between current transmitted or received bytes and their values one second ago.


#!/bin/bash

# This shell script shows the network speed, both received and transmitted.

# Usage: net_speed.sh interface
#   e.g: net_speed.sh eth0


# Global variables
interface=$1
received_bytes=""
old_received_bytes=""
transmitted_bytes=""
old_transmitted_bytes=""


# This function parses /proc/net/dev file searching for a line containing $interface data.
# Within that line, the first and ninth numbers after ':' are respectively the received and transmited bytes.
function get_bytes
{
    line=$(cat /proc/net/dev | grep $interface | cut -d ':' -f 2 | awk '{print "received_bytes="$1, "transmitted_bytes="$9}')
    eval $line
}


# Function which calculates the speed using actual and old byte number.
# Speed is shown in KByte per second when greater or equal than 1 KByte per second.
# This function should be called each second.
function get_velocity
{
    value=$1    
    old_value=$2

    let vel=$value-$old_value
    let velKB=$vel/1000
    if [ $velKB != 0 ];
    then
 echo -n "$velKB KB/s";
    else
 echo -n "$vel B/s";
    fi
}

# Gets initial values.
get_bytes
old_received_bytes=$received_bytes
old_transmitted_bytes=$transmitted_bytes

# Shows a message and waits for one second.
echo "Starting...";
sleep 1;
echo "";


# Main loop. It will repeat forever.
while true; 
do

    # Get new transmitted and received byte number values.
    get_bytes

    # Calculates speeds.
    vel_recv=$(get_velocity $received_bytes $old_received_bytes)
    vel_trans=$(get_velocity $transmitted_bytes $old_transmitted_bytes)

    # Shows results in the console.
    echo -en "$interface DOWN:$vel_recv\tUP:$vel_trans\r"

    # Update old values to perform new calculations.
    old_received_bytes=$received_bytes
    old_transmitted_bytes=$transmitted_bytes

    # Waits one second.
    sleep 1;

done

Howto Compile the Linux Kernel in GNU/Debian and Ubuntu

2009-10-11T12:01:00.014+02:00

NOTE: Tested in GNU/Debian Sid. Ubuntu versions should also work.

OBTAIN KERNEL SOURCE CODE:

Obviously the first step is obtaining the source code.

It is recommended to place and build linux kernel source code in /usr/src directory, although it is not required.

We create our "Linux_Kernel_Source" directory for this task.
$mkdir Linux_Kernel_Source
$cd Linux_Kernel_Source

Linux kernel source code is freely available in Internet:
http://www.kernel.org
specifically, version 2.6:
http://www.kernel.org/pub/linux/kernel/v2.6

We download and uncompress latest source code (2.6.31 when this article was written):
#aptitude install wget bzip2 # packages needed to get the kernel source code and uncompress it.
$wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.31.tar.bz2

Uncompress the source:
$tar xvjf linux-2.6.31.tar.bz2

/usr/src/linux is a symlink to linux sources or at least linux kernel headers. It is required.
#ln -s linux-2.6.31 /usr/src/linux

$cd linux-2.6.31

KERNEL CONFIGURATION:

There are several ways to configure the linux kernel build process. We are gonna use the console way (using make menuconfig).

#aptitude install ncurses-dev # This package is needed to execute make menuconfig.

NOTE: If we would want to execute make gconfig (gtk configuring way) we would need to install:
gtk+-2.0, glib-2.0 and libglade-2.0

We exec:
make menuconfig

A console menu will appear. There always are three options:
select: selects which kernel part to configure. Pressing SPACE key you can select if it is going to be built as a kernel module or built in within the kernel itself.
exit: To exit from the kernel part we are configuring or to exit the configuration process.
help: Provides good info about what choices do you have.

If you do not want to configure everything in the kernel again (It is huge!), you could search in the /boot directory for configuration files:

Every configuration file begins with config followed by its kernel version.

We copy one of them to our linux kernel source directory:
$cp /boot/config-2.6.26-1-686 /usr/src/linux

To select that configuration file you have to select "load alternate file" in the make menuconfig configuration process.
To make permament the changes you have done, and include them in the compilation, select "save alternate file" and save it as ".config"

BUILDING AND COMPILING THE KERNEL:

Once we are finished configuring the kernel compilation process, we are going to compile it.

To get some help about options we have:
$make help # shows all different options we could choose.

We now build the kernel and its modules:
$make

Then we install the kernel in /boot directory, as vmlinuz-"your kernel version"
#make install

To install kernel modules:
#make modules_install # installs kernel modules in /lib/modules/2.6.31

CREATING A INITRD IMAGE FILE

We need also to create a initrd image file to be able to boot in two steps:

#aptitude install initramfs-tools

#mkinitramfs -o /boot/initrd.img-2.6.31 2.6.31
We set the output image file using -o option.
We have also to indicate which kernel version are we using. e.g: 2.6.31

UPDATING GRUB:

Last step is setting correctly the bootloader so it will boot the recently compiled kernel.

We assume the GRUB bootloader.

Next lines show an example grub entry in /boot/grub/menu.lst file.

(hd0,6) and /dev/sda7 should be changed to match your system configuration.

title  Debian GNU/Linux, kernel 2.6.31
root  (hd0,6)
kernel  /boot/vmlinuz-2.6.31 root=/dev/sda7 ro
initrd  /boot/initrd.img-2.6.31

INSTALL GRUB IN YOUR DRIVE

NOTE: Be careful or you will not be able to boot your system.

/dev/sda is the hard disk where boot sector is installed, change it to match your system.
#grub-install /dev/sda

REFERENCE:

http://www.howtoforge.com/howto_linux_kernel_2.6_compile_debian

Installing Mediawiki using SQLite Database in GNU/Debian

2009-10-04T13:15:00.024+02:00

NOTE: These article commands have been tested in GNU/Debian Sid. They should also work in Ubuntu flavours.

THIS ARTICLE IS BASED ON:
http://linuxclues.blogspot.com/2008/04/installing-configuring-mediawiki-ubuntu.html
http://linuxclues.blogspot.com/2008/04/backup-restore-mediawiki-ubuntu.html

First we need to install php, apache and SQLite if they are not installed. This command will do the trick:
#apt-get install php5-sqlite

Following mediawiki recommendation we add some extensions to php for SQLite to work:
Edit /etc/php5/apache2/php.ini
Add these two lines in that file:

  extension=php_pdo_sqlite.so
  extension=php_pdo.so

To solve servername warning when launching apache daemon:
#echo "ServerName localhost" >> /etc/apache2/httpd.conf

We start apache web server:
#apache2ctl start

DOWNLOAD MEDIAWIKI SOURCE CODE

#cd /var/www

We get latest mediawiki source code tarball (current one when writting this article is 1.15.1):
#wget http://download.wikimedia.org/mediawiki/1.15/mediawiki-1.15.1.tar.gz

Uncompress it:
#tar xvfz mediawiki-1.15.1.tar.gz
#cd mediawiki-1.15.1
#ln -s mediawiki-1.15.1 mediawiki

We set writting permissions to config directory so we will be able to configure our wiki:
#chmod a+w config

CONFIGURING THE WIKI

We open a web browser: http://localhost/mediawiki/

We observe that: It detects correctly SQLite drivers!!

Some clues about configuring first time the wiki are pointed in this article:
http://linuxclues.blogspot.com/2008/04/installing-configuring-mediawiki-ubuntu.html

NOTE: SQLite is userless, and therefore requesting to fill usernames and passwords for it is pointless in configure page.
However it is needed to write something in those fields to continue the configuring process.

NOTE: SQLite Data directory field is needed to store SQlite database. Remember to give to it writting permissions!!

If everything goes fine you will get: Success!!

CONFIGURING LocalSettings.php FILE

Edit LocalSettings.php following http://linuxclues.blogspot.com/2008/04/installing-configuring-mediawiki-ubuntu.html instructions.

Now we set adequate permissions to this file:
#cd var/www/mediawiki
#mv config/LocalSettings.php . # mv LocalSettings.php to parent directory.
#chown root:www-data LocalSettings.php
#chmod 0640 LocalSettings.php

NOTE: When finished your configuration you should delete config directory to prevent the wiki being configured again.

CREATING A NORMAL USER

In the web browser: http://localhost/mediawiki

You will need to login as WikiSysop user.

Navigate to: SpecialPages --> Login in / create account --> Then create a new normal user account.

BACKING AND RESTORING THE SQLITE BASED MEDIAWIKI

SQLite has no users so we will not need a administrator user. Nevertheless we will set root permissions to prevent other users to access AdminSettings.php file:

Creating AdminSettings.php file
#cd /var/www/mediawiki
#cp AdminSettings.sample AdminSettings.php
#chown root:root AdminSettings.php
#chmod 600 AdminSettings.php

We will need php console cli command:
#aptitude install php5-cli # php command.

BACKING UP THE WIKI
Create the xml backup file:
#cd /var/www/mediawiki/maintenance
#php dumpBackup.php --current > ~/backup.xml

RESTORING THE WIKI
#cd /var/www/mediawiki/maintenance
#php importDump.php ~/backup.xml

REFERENCE:

href="http://www.mediawiki.org/wiki/Manual:SQLite

Creating a FEDORA 10 CHROOT Environment in DEBIAN SID

2009-03-15T01:40:00.006+01:00

Fedora is a linux distribution supported by a community: fedoraproject.org and by Red Hat enterprise.
Fedora (Wikipedia)

Current release name is Fedora 10.

Fedora packages are provided in rpm format. We can manage these packages using rpm tool, and use yum to deal with repositories.

Debian sid provides the rpm tool so our first task will be installing it in our Debian system:
#aptitude install rpm

This tool will allow us to install fedora packages in our debian system using a separate database and a different directory than / .

We create the directory to place our Fedora chroot environment:

$mkdir Fedora
$cd Fedora
$mkdir Distro

We are going to download the minimal amount of rpm packages required for our Fedora distro.

Navigating through fedora project web page we can find some mirrors, e.g:
http://glup.uv.es/mirror/fedora/linux/
http://ftp.uni-kl.de/pub/linux/fedora/linux/
Choose one near you.

Within those mirrors we find where packages are:
http://glup.uv.es/mirror/fedora/linux/releases/10/Fedora/i386/os/Packages/
http://ftp.uni-kl.de/pub/linux/fedora/linux/releases/10/Fedora/i386/os/Packages/

We can download every package we need using wget tool.
Although we only show the installing rpm command, you will have to download every rpm package prior to install it.
NOTE: Package version may not coincide, but the same package name and same installing order are mandatory.

If we need some file to satisfy a dependency, but don't know which package contains it, this web page can help us:
http://rpmfind.net

Our goal is to install a minimal working Fedora distro. Some important packages are needed to acomplish that: bash, rpm and yum.

Bash will provide us a shell, rpm is needed to manage rpm packages, and yum will allow us to continue installing packages in our chroot enviroment using some rpm repositories and solving dependency problems.

We begin installing the packages:
/home/foo/Fedora/Distro is the directory where our chroot environment will be placed.

#export FEDORA_DISTRO_DIR="/home/foo/Fedora/Distro"
rpm --root $FEDORA_DISTRO_DIR/ -i setup-2.7.4-1.fc10.noarch.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i filesystem-2.4.19-1.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i basesystem-10.0-1.noarch.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libgcc-4.3.2-7.i386.rpm

"--nodeps" option is needed because glibc package has cross dependencies.
rpm --root $FEDORA_DISTRO_DIR/ -i glibc-2.9-2.i686.rpm --nodeps

rpm --root $FEDORA_DISTRO_DIR/ -i ncurses-base-5.6-20.20080927.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i ncurses-libs-5.6-20.20080927.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i bash-3.2-29.fc10.i386.rpm

Bash is now installed so we could execute chroot if we would want.

rpm --root $FEDORA_DISTRO_DIR/ -i tzdata-2008h-1.fc10.noarch.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i glibc-common-2.9-2.i386.rpm

rpm --root $FEDORA_DISTRO_DIR/ -i ncurses-5.6-20.20080927.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libsepol-2.0.33-1.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i libselinux-2.0.73-1.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libstdc++-4.3.2-7.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i pcre-7.8-1.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i zlib-1.2.3-18.fc9.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i info-4.12-4.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i grep-2.5.1a-61.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libattr-2.4.43-1.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libacl-2.2.47-3.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i libcap-2.10-2.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i audit-libs-1.7.8-6.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i cracklib-2.8.12-2.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i cracklib-dicts-2.8.12-2.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i db4-4.7.25-5.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i coreutils-6.12-17.fc10.i386.rpm -nodeps
rpm --root $FEDORA_DISTRO_DIR/ -i pam-1.0.2-2.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i popt-1.13-4.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i logrotate-3.7.7-1.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i bzip2-libs-1.0.5-3.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i compat-db45-4.5.20-5.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i elfutils-libelf-0.137-3.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i readline-5.2-13.fc9.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i lua-5.1.4-1.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i file-libs-4.26-3.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i nspr-4.7.2-2.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i sqlite-3.5.9-2.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i nss-3.12.2.0-3.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i crontabs-1.10-23.fc10.noarch.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i e2fsprogs-libs-1.41.3-2.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i keyutils-libs-1.2-3.fc9.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i krb5-libs-1.6.3-16.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libidn-0.6.14-8.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i ca-certificates-2008-7.noarch.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i openssl-0.9.8g-11.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i cyrus-sasl-lib-2.1.22-19.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i openldap-2.4.12-1.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i libssh2-0.18-7.fc9.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i libcurl-7.18.2-7.fc10.i386.rpm 
rpm --root $FEDORA_DISTRO_DIR/ -i curl-7.18.2-7.fc10.i386.rpm
rpm --root $FEDORA_DISTRO_DIR/ -i rpm-libs-4.6.0-0.rc1.7.i386.rpm --nodeps
rpm --root $FEDORA_DISTRO_DIR/ -i rpm-4.6.0-0.rc1.7.i386.rpm

RPM ACOMPLISHED!! We would be able to enter the chroot environment an install packages with rpm.

Packages needed to create new users and change their passwords:

rpm -i shadow-utils-4.1.2-8.fc10.i386.rpm
rpm -i gamin-0.1.9-6.fc10.i386.rpm --nodeps
rpm -i glib2-2.18.2-3.fc10.i386.rpm
rpm -i libuser-0.56.9-1.i386.rpm
rpm -i passwd-0.75-2.fc9.i386.rpm

Terminal to login in the system: (actually we will use agetty instead)
rpm -i mingetty-1.08-2.fc9.i386.rpm

Packages needed to install YUM tool.

rpm -i expat-2.0.1-5.i386.rpm 
rpm -i gdbm-1.8.0-29.fc10.i386.rpm
rpm -i python-libs-2.5.2-1.fc10.i386.rpm --nodeps
rpm -i python-2.5.2-1.fc10.i386.rpm
rpm -i libgpg-error-1.6-2.i386.rpm
rpm -i libgcrypt-1.4.3-2.fc10.i386.rpm
rpm -i libksba-1.0.4-1.fc10.i386.rpm
rpm -i pth-2.0.7-7.i386.rpm
rpm -i dirmngr-1.0.2-1.fc10.i386.rpm
rpm -i libusb-0.1.12-20.fc10.i386.rpm
rpm -i chkconfig-1.3.38-1.i386.rpm
rpm -i pinentry-0.7.4-5.fc9.i386.rpm
rpm -i gnupg2-2.0.9-3.fc10.i386.rpm
rpm -i gpgme-1.1.7-1.fc10.i386.rpm
rpm -i pygpgme-0.1-8.fc9.i386.rpm
rpm -i python-iniparse-0.2.3-3.fc9.noarch.rpm
rpm -i rpm-python-4.6.0-0.rc1.7.i386.rpm
rpm -i python-urlgrabber-3.0.0-10.fc10.noarch.rpm
rpm -i libxml2-2.7.2-1.fc10.i386.rpm
rpm -i yum-metadata-parser-1.1.2-10.fc10.i386.rpm
rpm -i yum-3.2.20-3.fc10.noarch.rpm

Yum is now installed in our system. So we add a repository.

We edit and add this into $FEDORA_DISTRO_DIR/etc/yum.conf file:
Change baseurl to the mirror url you choose.

[Fedora10]
name=Fedora 10
baseurl=http://ftp.uni-kl.de/pub/linux/fedora/linux/releases/10/Fedora/i386/os

NOTE: We will need to run: #yum update to take into account this new repository, when our chroot environment will be working.

MOUNTING DIRECTORIES
Lets mount the directories needed for our chroot environment:

# cd $FEDORA_DISTRO_DIR
# mount --bind /proc proc
# mount --bind /sys sys
# mount --bind /proc/bus/usb proc/bus/usb
# mount --bind /dev dev
# mount --bind /dev/shm dev/shm
# mount --bind /dev/pts dev/pts
# mount --bind /tmp tmp     # to use X-Windows
# mkdir -p lib/init/rw
# mount --bind /lib/init/rw lib/init/rw

We copy these files to be able to resolve localhost and dns

# cp /etc/hosts $FEDORA_DISTRO_DIR/etc/
# cp /etc/resolv.conf $FEDORA_DISTRO_DIR/etc/

Create a working /etc/mtab file:
# cp /etc/mtab $FEDORA_DISTRO_DIR/etc #edit this file to correct values. e.g:

proc /proc proc rw,noexec,nosuid,nodev 0 0
sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0
udev /dev tmpfs rw,mode=0755 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=620 0 0

NOTE: You can left proc and sysfs only, if you want.

ENTER INTO THE CHROOT JAIL:
Sid:# chroot $FEDORA_DISTRO_DIR

We are now in the Fedora 10 environment!!

Now we import the repository key:

Fedora:# wget http://ftp.uni-kl.de/pub/linux/fedora/linux/releases/10/Fedora/i386/os/RPM-GPG-KEY-fedora-i386
Fedora:# rpm --import RPM-GPG-KEY-fedora-i386
Fedora:# yum update

We can install new packages. e.g:

Fedora:# yum install man-pages
Fedora:# yum install man

Fedora:# yum install iputils #ping utility.

Before login in the standar way we need to CREATE A NEW USER AND CHANGE PASSWORDS:

To solve password changing problem: "passwd: User not known to the underlying authentication module"

Fedora:# yum install shadow-utils
Fedora:# pwconv    #to create /etc/shadow file.

We create fedoraUser:
Fedora:# adduser fedoraUser

Fedora:# passwd    # change root password.
Fedora:# passwd fedoraUser   # change fedoraUser password.

To ENTER INTO THE CHROOT JAIL IN THE STANDARD WAY, without CONTROLLING TTY error, we will use agetty command:

Fedora:# yum install util-linux-ng #to obtain agetty command.
Sid:$ su -c "chroot ChDistro /sbin/agetty 38400 $(tty)"

We can login as fedoraUser.

USING SID X-Windows:

Sid:$xhost +local:`hostname` # Allow connections from local machine.

Fedora:$ export DISPLAY=:0.0    if you are using 0.0 display in Sid distro.
Fedora:$ xclock

INSTALLING EMACS

Fedora:# yum install emacs

We get this error, to solve it we will install some fonts e.g dejavu ones:

# Emacs fonts problems it is solved installing some fonts:
"Pango-CRITICAL **: No fonts found:
This probably means that the fontconfig
library is not correctly configured. You may need to
edit the fonts.conf configuration file. More information
about fontconfig can be found in the fontconfig(3) manual
page and on http://fontconfig.org"

Fedora:# yum install dejavu-fonts

INSTALLING FIREFOX

Fedora:# yum install firefox

Some errors occur:

D-Bus library appears to be incorrectly set up; failed to read machine uuid: Failed to open "/var/lib/dbus/machine-id": No such file or directory

solved with:
#dbus-uuidgen --ensure

GConf Error: Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://www.gnome.org/projects/gconf/ for information. (Details - 1: Failed to get connection to session: Failed to execute dbus-launch to autolaunch D-Bus session)

solved installing:
#yum install dbus-x11 so /usr/bin/dbus-launch will be available.

SOUND SUPPORT IN OUR CHROOT

Fedora:# ls -l /dev/snd/*
We see a group number, 29 in my system. This is audio group in my Sid distro.

Fedora:# groupadd -g 29 audio
Fedora:# ls -l /dev/snd*
Fedora:# usermod -a -G audio fedoraUser

we can check if audio group was added:
Fedora:# groups fedoraUser

I use alsa in my system so:
Fedora:# yum install alsa-lib

Now we can use sound applications in our Fedora chroot environment.

Calculating Prime Numbers using python

2009-01-31T18:11:00.007+01:00

This blog article shows a python exercise which consists on calculating some prime numbers using trial division algorithm.

You can copy this code in a script file and then execute it!


!/usr/bin/env python

#Prime numbers
import sys
import math

print "Prime numbers"

#Asks user how many numbers he wants to calculate.
top = int(raw_input("How many prime numbers do you want to calculate?: "))

if (top <1 ) :
    print "Error: Invalid number. It must be greater than one"
    sys.exit

#Initializing some variables
a = 3    # first number to test if it is prime.
result = [2]  # result list begins with prime number 2.
num = 1   # number of already calculated primes.
print 2,

while num < top : # main loop
    cont = 0

    # Performs the division test
    while 1 :
        divisor = result[cont]   # we only test with already calculated prime numbers.
        
        (quotient, remainder) = divmod(a,divisor)  # calculates quotient and remainder at the same time.

        if (remainder) :
            if divisor <= quotient :
                cont += 1 
            else:
                result.append(a)
                print a,  # number a is a prime.
                num += 1
                break
        else:
            break   # number a is not a prime

    a += 1   # calculate next number to test.

This other script avoids testing numbers that are multiple of 2,3,5 or 7. Also calculates the integer square root to obtain the higher divisor limit to test for each number.


#!/usr/bin/env python

#Prime numbers
import sys
import math

print "Prime numbers"

#Asks user how many numbers he wants to calculate.
top = int(raw_input("How many prime numbers do you want to calculate?: "))

if (top <1 ) :
    print "Error: Invalid number. It must be greater than one"
    sys.exit

#Initializing some variables
a = 11   # first number to test if it is prime
statea = 0
stateb = 0
result = [7]  # result list begins with prime number 7
num = 4   # number of already calculated primes.
print 2, 3, 5, 7,

while num < top : # main loop
    cont = 0

    #Calculates the integer square root of a
    low = 1
    upper = a
    while (upper - low) > 1 :
        med = (low + upper)/2
        temp = med * med
        if temp > a :
            upper = med
        else:
            low = med
            if temp == a :
                break

    # Performs the division test
    while 1 :
        divisor = result[cont]
        if (a % divisor) :
            if divisor <= low :
                cont += 1
            else:
                result.append(a)
                print a,  # number a is a prime
                num += 1
                break
        else:
            break   # number a is not a prime

    # Calculates next number to test if it is a prime.
    if (stateb == 4) or (stateb == 6) :
        a += 6
        stateb += 1
    elif statea :
        a += 4
        statea = 0
        if stateb == 7 :
            stateb = 0
        else :
            stateb += 1
    else :
        a += 2
        statea = 1
        stateb +=1

Installing Adobe Flash Player Plugin in GNU/Debian Sid

2008-12-26T15:55:00.005+01:00

There are several available installation versions: tar.gz, deb and rpm.

I try deb package version because it solved me all unsatisfied dependencies that made iceweasel(firefox) crash.

First we download .deb package.
$wget http://fpdownload.macromedia.com/get/flashplayer/current/install_flash_player_10_linux.deb

Now we install the package.
#dpkg -i install_flash_player_10_linux.deb

Solving dependencies problems
#apt-get -f install

You can now run iceweasel with adobe flash plugin support.

NOTE:Another way of installing this plugin is the Debian installation way:

supposing you have non-free repositories added in your sources.list file.

#aptitude install flashplugin-nonfree

It automatically installs tar.gz version from adobe page

However dependencies are not the same as .deb package and my iceweasel crashed.

REFERENCE URLs

http://get.adobe.com/es/flashplayer/

http://www.adobe.com/es/products/flashplayer/productinfo/instructions/

Installing GNU/Debian Sid in Ubuntu Hardy using debootstrap and chroot

2008-09-21T21:20:00.012+02:00

This article explains how to install GNU/Debian Sid in a previously installed Ubuntu Hardy System. We will use debootstrap and chroot tools to accomplish that. This how-to is not focused on security, it does not tell how to create a restricted chroot environment to improve security.

Ubuntu is a GNU/Debian based distro. Every six months they take GNU/Debian Unstable packages and make a new Ubuntu distribution.
Debian Sid provides more and newer packages. Ubuntu is configured for easiness. Debian has less preconfiguration instead.

chroot runs a command with a special root directory.
chroot comes as part of coreutils package.
$sudo aptitude install coreutils

debootstrap command bootstraps a basic Debian system (it can also bootstrap other systems).
$sudo aptitude install debootstrap

$ls /usr/share/debootstrap/scripts/ #shows which distros and versions you can install with debootstrap:

breezy  edgy  etch-m68k  gutsy  hoary  lenny  sarge  sarge.fakechroot  warty  woody 
 dapper  etch  feisty  hardy  hoary.buildd  potato  sarge.buildd  sid warty.buildd  woody.buildd

INSTALLATION BEGINNING

First of all we create the directory where Debian Sid will be installed.
$mkdir DebianSid

CREATING A LOOPBACK IMAGE TO STORE DEBIAN SID

This step is only necessary if you plan to boot your system from your Debian Sid chroot environment.

$sudo dd if=/dev/zero of=DebianSidFile bs=1048576 count=10000 #We create DebianSidFile with 10 gigabyte capacity.

$sudo mkfs.ext3 -b 4096 -L DSid DebianSidFile #Ext3 filesystem creation.

$sudo mount DebianSidFile DebianSid -t ext3 -o loop #mounting it on DebianSid directory.

INSTALLING A MINIMAL SYSTEM

$sudo debootstrap --variant=minbase --verbose sid DebianSid http://ftp.debian.org

it downloads, unpacks and installs a minimal Debian base system.

MOUNTING IMPORTANT FILESYSTEMS

$sudo mount --bind /proc DebianSid/proc

$sudo mount --bind /sys DebianSid/sys

$sudo mount --bind /tmp DebianSid/tmp

$sudo mount --bind /dev DebianSid/dev

$sudo mount --bind /dev/pts DebianSid/dev/pts

NOTE: if you wanna share your user application configurations between Ubuntu and Debian you can mount home directory.

$sudo mount --bind /home DebianSid/home

Copying the static lookup table for host names:

$sudo cp /etc/hosts DebianSid/etc/

To resolve dns:

$sudo cp /etc/resolv.conf DebianSid/etc/

ENTERING INTO THE CHROOT ENVIRONMENT

$sudo chroot DebianSid

If we execute: #cat /etc/issue it will show:

Debian GNU/Linux lenny/sid \n \l

so we are in Debian Sid!!

NOTE: Setting the hostname also changes the original system hostname, better not to change it: e.g: #hostname DebianChrootSid

ADDING SEVERAL TOOLS TO OUR SYSTEM

Updating the package system database:
#apt-get update

Dialog interface to show messages:
#apt-get install dialog

To obtaing ping utility: #apt-get install inetutils-ping
We can test the network: #ping www.google.com

Installing less:
#apt-get install less

Small vi editor:
#apt-get install vim-tiny

apt-file: #apt-get install apt-file #to search for files and packages.
apt-file configuration: #apt-file update #This will take some time.

Installing man to read man pages: #apt-get install man-db

ADDING NEW USERS

#apt-get install adduser

adding user foo: #adduser foo

becoming that user: #su foo

INSTALLING AND CONFIGURING LOCALE SUPPORT

installing locales: #apt-get install locales

The easier way to configure locales is, using dialog interface, executing:
#dpkg-reconfigure locales

The hard way to configure locales is editing some configuration files:

we edit locale.gen file: #vi /etc/locale.gen

and uncomment the locale we want to generate:
e.g: #es_ES.UTF-8 UTF-8 for Spain

generate locales with: #locale-gen

After locales have been configured we can execute:

show available locales: #locale -a

selecting a locale: e.g: spanish locale: #export LANG="es_ES.UTF-8"

showing current locale: #locale

WAYS OF LAUNCHING OUR CHROOT ENVIRONMENT

STANDARD WAY

$sudo chroot DebianSid /bin/bash

This method maintains a lot of variables from the original environment, I dont like it.

LOGGING IN WAY

NOTE: To use this method you need to previously create a new user (with adduser) and assign a password to root (with passwd) because is not possible to log in as root user. You will have to login as a standard user and then execute su command to become root.

tty command tells which terminal is standard output attached to: eg: /dev/pts/3

$sudo chroot DebianSid /sbin/getty 38400 `tty`

after you type sudo password you are offered a login prompt to enter in the chroot environment.

INSTALLING X-WINDOWS

Installing x-windows: #apt-get install xorg

Copying xorg configuration file from Ubuntu:

$sudo mv /etc/X11/xorg.conf DebianSid/etc/X11/

window manager: #apt-get install ion2

starting X: #startx /usr/bin/ion2 -- :1

NOTE: if you cannot start the X server as a normal user change in /etc/X11/Xwrapper.config

allowed_users=console to allowed_users=anybody

SHOWING X APPLICATIONS IN THE UBUNTU DISPLAY

On ubuntu to allow connections from anyone:

$xhost +

Better open only local connections: (in Ubuntu)

$hostname #shows the hostname

$xhost +local:`hostname`

now in the chroot environtment:

$export DISPLAY=:0.0 # X display in Ubuntu.

$xclock # an x window clock will show on the Ubuntu desktop screen.

this will work because we have shared X11 socket through /tmp dir with Ubuntu.

INSTALLING MPLAYER TO TEST VIDEO AND SOUND

After installing mplayer, video and sound should work fine:

Installing mplayer: #apt-get install mplayer

INSTALLING GNOME

Installing gnome: #apt-get install gnome

Starting gdm: #/etc/init.d/gdm start

NOTE: There is a problem with some gnome-applets because their configuration are shared with Ubuntu.

BOOTING FROM YOUR CHROOT ENVIRONMENT USING GRUB

At booting time you will be able to choose between booting from Ubuntu or from your chrooted Debian Sid.

You will have to add some lines to /boot/grub/menu.lst file to boot from your chroot environment.
Best idea is copying the lines at /boot/grub/menu.lst which ubuntu uses to boot Ubuntu and adapt them.

These are from my system. You will have to change 2.6.24-21 to your linux kernel version, loop=/usr/local/DebianSidFile to your DebianSidFile location, and your root device identifier.

title           kernel 2.6.24-21-generic DebianSid Loop
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.24-21-generic root=UUID=a31628c8-5402-4319-b9cd-6a6183d43bc5 loop=/usr/local/DebianSidFile ro 
initrd          /boot/initrd.img-2.6.24-21-generic
quiet

NOTE: You have to use an ubuntu initrd.img file in order to understand the loop option.

Copy the necessary kernel modules into our chroot environment:
$sudo cp -a /lib/modules/2.6.24-21-generic DebianSid/lib/modules

And reinstall grub: $sudo grub-install /dev/sda #supposing master boot record is in /dev/sda device.

Now you can reboot your system into your chroot environment.

REFERENCE: http://ubuntuforums.org/showthread.php?t=24575

Joining two AVI files with MENCODER

2008-08-20T18:39:00.005+02:00

It is usual having an avi film split into two cdrom sized files of 700 megabytes each.

mencoder utility allows us to concatenate these two parts into a new reintegrate file.

mencoder (MPlayer's Movie Encoder) is a tool MPlayer provides to encode multimedia contents into files.
It supports among others, MPEG-4 video, libavcodec codecs, and PCM/MP3/VBRMP3 audio formats.
mencoder also possesses stream copying abilities and a powerful filter system (crop, expand, flip, ....).

So we have a film split into two files e.g: foo1.avi and foo2.avi, both with the same encoding characteristics (window size, codecs, bitrate...),

We execute this command that produces an output file called foo.avi which is the result of concatenating foo1.avi and foo2.avi files.
$mencoder -oac copy -ovc copy -forceidx foo1.avi foo2.avi -o foo.avi

The command options mean:
* -oac output audio codec
* -ovc output video codec
* -o output file name
* -forceidx forces creation of a new index.
copy means copying the original stream and do not change the codec it is encoded into (because of that it is very fast).

more info executing: $man mencoder

INSTALLING MENCODER

Ubuntu and Debian: $sudo aptitude install mencoder
Compiling, Configuring and Installing MPlayer on a Ubuntu (Linux based) System.

Downloading, Compiling and Installing MPlayer on a Ubuntu System

2008-08-15T14:02:00.012+02:00

We are going to download MPlayer sources and binary codecs, configure, compile and install them on our Ubuntu system.

I do not want a graphical interface, so I will compile MPlayer without it.

DOWNLOADING MPLAYER SOURCES

We first download the sources: (I pick up the latest source version, if it does not work pick up latest stable one)

(I choose to download it from a German mirror: MPlayer source download page)
$wget http://www7.mplayerhq.hu/MPlayer/releases/mplayer-export-snapshot.tar.bz2

DOWNLOADING BINARY CODECS

MPlayer binary codecs download page

As I have a Linux x86 platform ,I choose its corresponding package:
$wget http://www7.mplayerhq.hu/MPlayer/releases/codecs/essential-20071007.tar.bz2

This page shows an updated list of supported codecs: Codec Status page

In order to install the binary codecs

We create the directory where we will place the codecs:
$sudo mkdir /usr/local/lib/codecs

We untar the codecs and then move them into their place:
$tar xvfj essential-20071007.tar.bz2
$cd essential-20071007/
$sudo cp * /usr/local/lib/codecs

CONFIGURING OSD FONTS

To be able to support truetype fonts:
$sudo aptitude install libfreetype6-dev

Look after this directory to find some fonts on your system: /usr/share/fonts/...
To install some fonts: $sudo aptitude install ttf-freefont

Now we create a symlink to the font file we choose:
$cd #We go to our home directory:
$mkdir .mplayer
$cd .mplayer
$ln -s /usr/share/fonts/truetype/freefont/FreeSans.ttf subfont.ttf

Our subtitle font will be automatically selected

NOTE: Another way to select a font file is using -font switch when executing mplayer command.
e.g: $mplayer -font /usr/share/fonts/truetype/freefont/FreeSans.ttf -vo x11 -framedrop ....

Some more font configuration info.

COMPILING MPLAYER SOURCES

First we untar the sources:
$tar xvfj mplayer-export-snapshot.tar.bz2
$cd mplayer-export-2008-08-13/

We choose and add some video drivers:
x11 support ----> $sudo aptitude install libx11-dev libxext-dev
Xv support -----> $sudo aptitude install libxv-dev
AA library support ----> $sudo aptitude install libaa1-dev
Alsa sound support ----> $sudo aptitude install libasound2-dev
Add ogg theora support ----> $sudo aptitude install libogg-dev libtheora-dev

Avoid X screensaver activation.
$sudo aptitude install libxss-dev

And finally configure, compile and install mplayer:
$./configure
$make
$sudo make install

Now we can enjoy our multimedia files:
e.g $mplayer -vo xv -framedrop -sub foo.srt foo.avi

NOTE: If you want to switch off MPlayer console messages pass this argument -msglevel all=0 when calling mplayer command.
e.g $mplayer -vo xv -framedrop -msglevel all=0 -sub foo.srt foo.avi

You can obtain more info executing $man mplayer.

NOTE: Mplayer also provides mencoder utility, which you can use to encode multimedia files.

REFERENCE URLS:
MPlayer official site.
Installation instructions from MPlayer site. This text is also available within MPlayer sources.

Connecting to Internet using a Sony Ericsson K530i mobile phone in Ubuntu (Linux) via USB cable

2008-08-12T21:30:00.014+02:00

We are going to connect our Ubuntu system to Internet using a Sony Ericsson K530i phone via a usb cable.

First of all we switch on our phone, we insert the pin number and then connect the usb cable that came with the phone to our K530i and to our computer.

A menu presenting three choices will appear on the phone screen:

File transfer
Phone mode
Print

We select Phone mode.

Now our phone is ready to use the usb cable.

There are two ways to connect to Internet via USB:

Emulating a ethernet device through a usb cable.
Using the K530i mobile phone as a usb serial modem.

EMULATING A ETHERNET DEVICE THROUGH USB CABLE

Our system Linux kernel has to already be compiled with cdc_ether module support. This module performs the emulation.

Let's configure our phone, we go to:
Menu->Settings->Connectivity->USB->USB Internet->USB data accounts
and select our Internet ISP provider account.

If there is not an already configured account we shall create a new account:
Menu->Settings->Connectivity->Data comm.->Data accounts->New account

Some APNs from Spanish Internet providers are:

Movistar: movistar.es
Vodafone: ac.vodafone.es
Yoigo: internet
Orange: internet

Usually user and password are not needed.

At the end, we establish the connection:
Menu->Settings->Connectivity->USB->USB Internet->Turn on

To check what has happened, we open a console and execute:
$ifconfig

An interface like usb0 with its IP address correctly configured will appear.

When we finish navigating, we switch off the connection:
Menu->Settings->Connectivity->USB->USB Internet->Turn off

USING THE K530i MOBILE PHONE AS A USB SERIAL MODEM

Our K530i phone will receive AT commands an will act as a USB serial modem.

First we install wvdial package:
$sudo aptitude install wvdial

If our modem is correctly connected through the usb cable some serial devices will show:

$ls -l /dev/ttyACM*


crw-rw---- 1 root dialout 166, 0 2008-08-12 19:50 /dev/ttyACM0
crw-rw---- 1 root dialout 166, 1 2008-08-12 19:50 /dev/ttyACM1

Now we need to configure wvdial so we create in our home directory a file called .wvdialrc

e.g:

[Dialer Defaults]
Phone = *99***1#
username = ''
password = ''
Modem = /dev/ttyACM0
Baud = 460800
Stupid Mode = 1
Init1 = ATZ
Init3 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ISDN = 0
Modem Type = Analog Modem

[Dialer Vodafone]
Init4 = AT+CGDCONT=1,"IP","ac.vodafone.es";

[Dialer Movistar]
Init4 = AT+CGDCONT=1,"IP","movistar.es";

[Dialer Yoigo]
Init4 =AT+CGDCONT=1,"IP","internet";

[Dialer Masmovil]
Init4 =AT+CGDCONT=1,"IP","internetmas";

[Dialer Simyo]
Init4 =AT+CGDCONT=1,"IP","gprs-service.com";


[Dialer Pin]
Init2 = AT+CPIN="8888"      #write your pin here.

This configuration file will work for most Spanish ISPs.

e.g:

$wvdial Vodafone will establish the connection.

or

$wvdial Vodafone Pin for the first time, to set the pin number too.

To stop it, simply press ctrl+c.

If your have another provider you will have to add an appropriate Init4 line with your provider APN. Some operators also change the Phone number.

Hello World program examples

2008-07-06T20:36:00.012+02:00

Hello World is the first program every user usually codes when he learns a new programming language.

Its goal is learning the basics to edit, compile and execute a program which sends a "hello world" string to standard output.

We have used an Ubuntu Hardy distro based system. Most commands will serve to other distros as well, like Debian.

BASH Shell Scripting Hello World

bash command line interpreter is usually already installed in your system.

if it is not installed we type: $sudo aptitude install bash

Now we create hello.sh script using whatever text editor we prefer.
e.g: $gedit hello.sh

Copy this lines into your hello.sh script

#!/bin/bash
echo "hello world"

Bash shell scripting is an interpreted language so we have not to compile anything. We directly execute the shell script file:

We give the shell script execution permissions:
$chmod a+x hello.sh

and launch the program
$./hello.sh

PYTHON Scripting Hello World

If you do not have python installed in your system, exec:

$sudo aptitude install python

Create a text file called hello.py with your favorite editor and copy these lines:

#!/usr/bin/python
print "hello world"

Because python is an interpreted language we execute directly the python script:

Add execution permissions:
$chmod a+x hello.py

Execute your hello world python script:
$./hello.py

C Language Hello World

We need a compiler because C is a compiled language:
$sudo aptitude install gcc

In order to be able to use standard input output system:
$sudo aptitude install libc6-dev

Using our favorite text editor, we create hello.c file.

Copy this program within hello.c file:

#include <stdio.h>

main ()
{
  printf("hello world\n");
}

We compile hello.c file to create hello binary executable file:
$gcc -o hello hello.c

Add execution permissions:
$chmod a+x hello

Execute the binary file:
./hello

C++ Language Hello World

First we install the c++ compiler:
$sudo aptitude install g++

This g++ virtual package installs the g++ compiler and also the c++ standard library:
e.g: g++-4.2, libstdc++6-4.2-dev

Type this hello.cc file copying this following code:

#include <iostream>

main()
{
   std::cout << "Hello World\n";
}

We compile hello.cc program:
$g++ -o hello hello.cc

We give execution permissions and execute hello binary file:
$chmod a+x hello
$./hello

JAVA Hello World

Java is a language which is compiled into intermediate code called java bytecodes.
Java bytecodes are executed in a runtime environment whose name is Java Virtual Machine (JVM)

In order to install the Java Virtual Machine
$sudo aptitude install openjdk-6-jre

and to install javac java compiler.
$sudo aptitude install openjdk-6-jdk

We create with a text editor a file called HelloWorld.java

NOTE: File name must be the same as the class, so we will call both HelloWorld

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

Generating java bytecodes:
$javac -verbose HelloWorld.java

A file called HelloWorld.class has been generated.

We are going to execute it within the java virtual machine:
$java HelloWorld

EMACS LISP (ELISP) Hello World

Lisp is an old programming language with a lot of dialects.
One of them is ELISP which is the language emacs editor is written with.

First we open an emacs session:
$emacs

Now we execute the command eval-expression:
C-: or M-x eval-expression RET

in the minibuffer prompt we write:
(message "hello world") RET

and "hello world" will appear in emacs mini buffer.

Qt C++ Hello World

Beginning with Qt: Introduction, Installing Qt Framework, Qt Hello world

Emacs Quick Introduction

2008-06-22T13:48:00.006+02:00

Installing emacs in a Ubuntu or Debian distro
$sudo aptitude install emacs

Launching emacs
$emacs

If you want to launch emacs in a console without X support, simply exec:
$emacs -nw

Notation:
C-x means mantain pressed control key and then press x key.

Reseting input buffer
C-g resets command input buffer. It is great if you mistyped a command.

Displacement commands:
C-n goes to next line
C-p goes to previous line
C-f goes to next character
C-b goes to previous character
C-a goes to the begining of the line
C-e goes to the end of the line

Deleting, cutting and pasting text
C-d deletes character under the cursor
C-k cuts from the cursor position until the end of the line.
C-y pastes previous cut text.

Undo command
C-x u undoes previous command.

Dealing with files
C-x C-f opens a file
C-x C-w saves current file.

Closing emacs
C-x C-c closes emacs.

Passing arguments to commands:
E.g: C-u 8 C-n Advances eight lines.

Reading emacs self-documentation:
C-h t opens emacs tutorial

These are the minimal set of commands to work with emacs like a notepad.

Emacs is an extremely powerful and flexible text editor. You are not even on the surface of emacs potential. I recommend you to study and use it.

Backing and Restoring Mediawiki in Ubuntu

2008-04-27T19:48:00.015+02:00

We are going to learn how to back up and restore our Mediawiki installed on a Ubuntu system.

To acomplish that we will execute some wiki maintenance commands.
These maintenance commands will be accesible after configuring AdminSettings.php file.

CONFIGURING AdminSettings.php FILE

AdminSettings.sample from the Mediawiki examples documentation will serve us as a model file to start.

We copy it into mediawiki configuration directory in /etc and assign the correct owner and permissions.

$sudo cp /usr/share/doc/mediawiki1.10/examples/AdminSettings.sample /etc/mediawiki1.10/AdminSettings.php
$sudo chown root:root /etc/mediawiki1.10/AdminSettings.php
$sudo chmod 600 /etc/mediawiki1.10/AdminSettings.php

Now we are going to edit AdminSettings.php file
$gksudo gedit /etc/mediawiki1.10/AdminSettings.php

Change these two variables using the parameters you used when creating the wiki database: e.g: wikiuser and its password.
$wgDBadminuser = 'DB user name'
$wgDBadminpassword = 'DB password'

Now that AdminSettings.php file is properly configured we are gonna back up and restore the wiki.

BACKING UP THE WIKI

dumpBackup.php command will back up our wiki:

$cd /var/lib/mediawiki1.10/maintenance
$sudo php dumpBackup.php --current > ~/foo_backup.xml

NOTE: --full option backups history of pages, not only last version as --current does.

RESTORING THE WIKI

importDump.php is the command we need:

$cd /var/lib/mediawiki1.10/maintenance
$sudo php importDump.php ~/foo_backup.xml

If after importing the xml file we still do not see anything in the wiki, we shall exec:
$sudo php rebuildrecentchanges.php
or
$sudo php update.php

NOTE: Those previous commands only back up and restore the text part of the wiki. They just create an xml with text.

Following commands shows how to backup and restore images in your wiki:

BACKING UP THE IMAGES OF YOUR WIKI

NOTE: As now, the wiki is placed mostly in /var/lib/mediawiki directory, we will assume the wiki is placed there, instead of /var/lib/mediawiki1.10 . This also suites better new wiki versions.

We create the directory where we will store the wiki image files:
$mkdir image_backup_dir && cd image_backup_dir

dumpUploads.php command shows all wiki image file locations.

We use this command output to copy all those files to our storage directory:
$sudo php /var/lib/mediawiki/maintenance/dumpUploads.php --base=$(pwd) | xargs -I foo cp 'foo' . -v

--base option tells dumpUploads.php command that all file places should be related to current directory.

xargs -I foo cp 'foo' . -v reads every file location from standard input and copies it to current directory.

If there has been no error, our current directory is populated now with the wiki image and media files.

RESTORING THE IMAGES OF YOUR WIKI

Once you have created image_backup_dir directory containing all the wiki image files we could restore them.

We execute importImages.php command and pass as argument the path to our image_backup_dir directory where all the images are:
$sudo php /var/www/mediawiki/maintenance/importImages.php image_backup_dir

Your wiki will show now all the images.

Installing and Configuring Mediawiki on a Ubuntu Gutsy Desktop System

2008-04-27T13:07:00.018+02:00

Mediawiki is the web based tool (wiki software) that Wikipedia uses to manage, store and serve its contents.

Mediawiki is written in PHP, and in this installation we will use MySQL as database management system (although it can be configured to use PostgreSQL)

Mediawiki is ditributed under the GNU GPL license.

INSTALLING MEDIAWIKI

First step is installing MySQL:
$sudo aptitude install mysql-admin mysql-server

It will ask you for MySQL root password. Then choose a secure password and type it.

Now we install Mediawiki itself:
$sudo aptitude install mediawiki

It will automatically check for apache and php dependencies.

Current mediawiki version is 1.10.

At installation I get this warning:
apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName

There is some info in this thread at ubuntu forums.

To get rid of the error:
$gksudo gedit /etc/apache2/httpd.conf

httpd.conf file is usually empty, and then we add this line:
ServerName localhost

After saving the file we check if the error is gone executing this command:
$sudo apache2ctl restart

SETTING MEDIAWIKI URL ALIAS

Open apache.conf file:
$gksudo gedit /etc/mediawiki1.10/apache.conf

Uncomment this line:
#Alias /mediawiki /var/lib/mediawiki1.10

You can change /mediawiki to whatever you wanna the wiki be named. e.g: /myWiki

Restart the apache server with:
$sudo apache2ctl restart
or
$sudo /etc/init.d/apache2 restart

Now you can navigate into your wiki:
http://localhost/mediawiki

There will appear a page with a link saying: "Please set up the wiki first."

It is okey. We click on the link so entering within the wiki configuration page: http://localhost/mediawiki/config/index.php

SETTING UP THE WIKI FOR THE FIRST TIME

We are at the configuration page: http://localhost/mediawiki/config/index.php and we assign adequated values for:

Wiki name: this name will appear at the top of your wiki pages.

e-mail, language, ...

Admin username: WikiSysop by default. This user will have all the privileges to mantain the wiki.

Admin password

I want a very simple configuration so I disable all email settings. So I won't be notified when a wiki page is changed, etc.

At database configuration part I leave the defaults:
NOTE: If you have an account and database already created, you can introduce those values here.

type: MySQL
host: localhost
name: wikidb 
username: wikiuser

I choose and set a password for this database user.

As I have no previously created a user and a database and I am very lazy and want mysql root user to create them, so I check superuser account:

Superuser account: checked
Superuser name: root
Superuser password: MySQL root password.

Let's go and click: Install Mediawiki! button

We arrive to a page that says Installation successful! if everything has gone fine

Next and last step is configuring LocalSettings.php file:

CONFIGURING LocalSettings.php FILE

There is comprehensive info about configuring LocalSettings.php file at Manual:LocalSettings.php

Checking out DefaultSettings.php file may also be interesting. It can be found at:
/var/lib/mediawiki1.10/includes/DefaultSettings.php

We begin editing the file:
$gksudo gedit /var/lib/mediawiki1.10/config/LocalSettings.php

We are gonna allow file uploads to our wiki:

search this variable $wgEnableUploads at LocalSettings.php file and set it to true:
$wgEnableUploads = true

GROUP CONFIGURATION

This wiki group configuration is going to be very simple. It consists on two user types, logged ones and anonymous users.

Anonymous users will be able to navigate through the wiki but will be unable to change or edit anything.

Logged users will be capable of reading, editing, uploading files, creating new wiki pages and creating new accounts for their friends. :)

Only WikiSysop will have privileges enough to delete or rename wiki pages.

In order to obtain this configuration, we have to copy this lines at the end of LocalSettings.php file:

#Global permissions (anonymous users too)

$wgGroupPermissions['*' ]['createaccount'] = false;
$wgGroupPermissions['*' ]['read'] = true;
$wgGroupPermissions['*' ]['edit'] = false;
$wgGroupPermissions['*' ]['delete'] = false;
$wgGroupPermissions['*' ]['createpage'] = false;
$wgGroupPermissions['*' ]['upload'] = false;
$wgGroupPermissions['*' ]['move'] = false;

#Logged users

$wgGroupPermissions['user' ]['createaccount'] = true;
$wgGroupPermissions['user' ]['read'] = true;
$wgGroupPermissions['user' ]['edit'] = true;
$wgGroupPermissions['user' ]['delete'] = false;
$wgGroupPermissions['user' ]['createpage'] = true;
$wgGroupPermissions['user' ]['upload'] = true;
$wgGroupPermissions['user' ]['move'] = false;

more info at:
Manual:$wgGroupPermissions

MOVING LocalSettings.php TO /etc

Finally we place LocalSettings.php file at /etc directory with its adequate permissions.

$cd /var/lib/mediawiki1.10
$sudo chown root:www-data LocalSettings.php
$sudo mv config/LocalSettings.php /etc/mediawiki1.10/
$sudo chmod 0640 /etc/mediawiki1.10/LocalSettings.php

CREATING A NORMAL USER ACCOUNT

Our wiki setup is completed!
We type http://localhost/mediawiki at the navigator and access to the wiki.

First time, we will have to enter using WikiSysop account and create a normal user one.
To do that, once you have logged as WikiSysop, go to Special pages and then to Log in / create account

Enjoy your wiki!!

Most info comes from Mediawiki site:
Installing_MediaWiki_on_Ubuntu_7.10_via_GUI_and_Synaptic

Linux System Directories and their Filesystems

2008-03-30T01:22:00.005+01:00

Executing ls / lists the top level of the root filesystem tree. There appear directories like:
/dev, /etc, /proc, /sys, /var, /tmp and others.

In this article we are going to deal with directories that have special filesystems associated with them.

For a general view of the filesystem hierarchy we can visit the Filesystem Hierarchy Standard page.

FHS standard is a set of guidelines about where to place files and directories within UNIX based operating systems.

Seeing which filesystems are mounted

Two commands allow us to see which filesystems and where are currently mounted in our system.

$mount
or
$cat /etc/mtab

Their response will be something like that:


 /dev/sda1 on / type ext3 (rw,errors=remount-ro)
 proc on /proc type proc (rw,noexec,nosuid,nodev)
 /sys on /sys type sysfs (rw,noexec,nosuid,nodev)
 varrun on /var/run type tmpfs (rw,noexec,nosuid,nodev,mode=0755)
 varlock on /var/lock type tmpfs (rw,noexec,nosuid,nodev,mode=1777)
 udev on /dev type tmpfs (rw,mode=0755)
 devshm on /dev/shm type tmpfs (rw)
 devpts on /dev/pts type devpts (rw,gid=5,mode=620)
 lrm on /lib/modules/2.6.22-14-generic/volatile type tmpfs (rw)
 securityfs on /sys/kernel/security type securityfs (rw)

We are interested specially in /proc, /sys, /var/run, /var/lock, /dev, /dev/shm, /dev/pts, /sys/kernel/security

/proc

procfs is a virtual file system, dynamically created in memory. It is usually mounted in /proc.

The proc file system provides an interface to kernel internal data structures. It allow us obtain information about the system and change certain kernel parameters at runtime (sysctl)

It can be accessed in a text mode way:

e.g: $cat /proc/meminfo #shows how memory is distributed.

/proc/sys directory allows us change kernel parameters.

e.g sudo echo "fooname" > /proc/sys/kernel/hostname #changes your box hostname.

Every process has a subdirectory at proc filesystem named by its pid.

mounting proc filesystem

$mount -t proc proc /mnt/proc # This command mounts a proc filesystem at /mnt/proc

/sys

sysfs is a ram-based filesystem initially based on ramfs. It provides
a means to export kernel data structures, their attributes, and the
linkages between them to userspace.

mounting sys filesystem

$mount -t sysfs sysfs /sys # The sys filesystem is always compiled and with this command you can access it.

tmpfs

Basically, tmpfs is a type of filesystem which uses RAM (and swap) as its device, but it is dynamically allocated, unlike a ramdisk. Therefore, it only takes as much RAM as it needs.

tmpfs is a filesystem, not a block device; you just mount it, and it's there. You don't need to use mkfs command.

This filesystem is used in several files and devices like /tmp, /dev/shm, etc.

Mounting a tmpfs filesystem

$sudo mount -t tmpfs tmpfs /mnt/tmpfs

/mnt/tmpfs will initially have a very small capacity, but as files are copied and created, the tmpfs filesystem driver will allocate more VM and will dynamically increase the filesystem capacity as needed. And, as files are removed from /mnt/tmpfs, the tmpfs filesystem driver will dynamically shrink the size of the filesystem and free VM resources, and by doing so return VM into circulation so that it can be used by other parts of the system as needed

Speed is the great advantage of tmpfs. As it usually resides in ram, accesses are almost instantaneous. Swap also provides good performance.

tmpfs is not preserved between reboots, because ram memory is volatile.

In order to avoid virtual memory exhaustion we can pass tmpfs size as an option:

$mount tmpfs /tmp -t tmpfs -o size=64m # Limits its size to 64 megabytes.

More info at:

http://www.ibm.com/developerworks/library/l-fs3.html#2

/dev

In Unix philosophy every device is attached to a file.
/dev directory is the place where device files are located.

http://en.wikipedia.org/wiki/Udev

udev is the device manager for the Linux 2.6 kernel series. Its primary function is managing device nodes in /dev. It is the successor of devfs and hotplug, which means that it handles the /dev directory and all user space actions when adding/removing devices, including firmware load.

$mount -t tmpfs udev /dev

/dev/pts

The devpts file system provides an interface to pseudo terminal (pty) devices. It is typically mounted at /dev/pts. A new pty device file is dynamically created when the /dev/ptmx pty master multiplex device is opened.

$mount -t devpts devpts /dev/pts

/dev/shm

This device implements POSIX shared memory.

E.g: Shared memory can be used as a quick way to share data between programs.

$mount -t tmpfs shm /dev/shm

/tmp

This place is where programs store their temporary files. It is not guaranteed that data will be preserved between program invocations.

/tmp should be cleared by the system every boot.

$sudo mount -t tmpfs tmpfs /tmp

securityfs

This is a filesystem used by linux kernel security modules.
It is mounted in /sys/kernel/security

mount -t securityfs securityfs /sys/kernel/security

/var/run

Contains system information data and it is cleared every system boot.

mount -t tmpfs varrun /var/run

/var/lock

Lock files should be placed in this directory.

mount -t tmpfs varlock /var/lock

There is some good info in the kernel documentation about filesystems.

To read it, run these commands:

$sudo aptitude install linux-doc-2.6.22
$zless /usr/share/doc/linux-doc-2.6.22/Documentation/filesystems/proc.txt.gz
$zless /usr/share/doc/linux-doc-2.6.22/Documentation/filesystems/sysfs.txt.gz
$zless /usr/share/doc/linux-doc-2.6.22/Documentation/filesystems/tmpfs.txt.gz

NOTE: Substitute 2.6.22 by your linux version.

Reverse Engineering Python Code with PyNSource

2008-03-26T10:16:00.007+01:00

PyNSource is a tool that allow us to obtain UML diagrams from python source code.

PyNSource Web Page

INSTALLING PyNSource ON AN UBUNTU GUTSY SYSTEM.

NOTE: You must have python already installed in your system. I assume 2.5 version.

$mkdir PyNSource
$cd PyNSource

Now we download the program and install it:

$wget http://www.atug.com/downloads/pynsource1.4c.zip
$unzip pynsource1.4c.zip
$sudo python setup.py install

We want to run the GUI so we need a graphical library:
$sudo aptitude install python2.5-wxgtk2.6

Current code does not work with version wxgtk2.6 so we need to update it:

$wget http://www.atug.com/andypatterns/code/pyNsourceGui1.4c-wx26.zip
$unzip pyNsourceGui1.4c-wx26.zip
$sudo cp pyNsourceGui-wx26.py /usr/lib/python2.5/site-packages/pynsource/

Finally we exec the GUI module
$python /usr/lib/python2.5/site-packages/pynsource/pyNsourceGui-wx26.py

This application presents some annoying bugs:

* There are problems when moving shapes on the screen. It does not refresh correctly.
* It is difficult to adjust page size when you try to print it.
* When you press right click button on the mouse to delete an object, usually it doesn't delete all the arrows that point to it, messing the schema.
* Saving and opening diagram feature is not implemented yet, so you cannot save temporary work.

Well, you know, this bugs are annoying, but it you dont like them, it is free software, so hack the code. :-)

GNU Readline Library Short Description

2008-03-14T21:35:00.016+01:00

GNU Readline is a software library that provides a set of functions that allow users to edit command lines as they are typed in.

Every program that uses this library provides the same user command line interface improving consistency between applications.

It is part of the GNU Project and it is licensed under the GPL.

Current version is 5.2 and it is used in projects like bash.

There are two editing modes available: Emacs (default) and Vi

Readline library includes additional functions to maintain a list of previously-entered command lines.
Exec this command to obtain more info about this feature:
$help history

INSTALLATION

In Debian and Ubuntu this library is packed in readline-common package.
$sudo aptitude install readline-common

Once installed, you can access a complete documentation using info command:
$info rluserman

SHORT KEYSTROKE REMINDER

NOTATION:
C-k means while ctrl key is mantained pressed, depress 'k' key.
M-k means while "meta" key is pressed, depress 'k' key.

Usually "meta" refers to ALT key, but if you have no meta key you can use ESC key instead.

Emacs mode commmands:

Movement

C-b Move back the cursor one character.
C-f Move one character forward.
DEL or Backspace Delete the character placed left at the cursor.
C-d Delete the character underneath the cursor.
C-_ or C-x C-u Undo the last editing command.

C-a Move to the beginning of the line.
C-e Move to the end of the line.
M-f Move forward a word.
M-b Move backward a word.
C-l Clear the screen, reprinting the current line at the top.

Killing and yanking (cutting and pasting) commands

C-k Kill the text from the current cursor position to the end of the line.
M-d Kill from the cursor to the end of the current word.
M-DEL Kill from the cursor the start of the current word.
C-w Kill from the cursor to the previous whitespace.

After killing(cutting) text, we yank(paste) it back into the line.

C-y Yank the most recently killed text back into the buffer at the cursor.
M-y Rotate the kill-ring, and yank the new top. You can only do this if the prior command is C-y or M-y.

Searching commands

C-r Searchs backwards on the previous commands you typed.
C-s Perform a forward search from the command line history you are now.

Passing arguments to a command

e.g: M-2 3 C-d means delete next 23 characters on input line.

CONFIGURING THE LIBRARY

GNU Readline keybindings and more can be changed editing ~/.initrc or /etc/initrc files.

URLs
GNU Readline Official page
GNU Readline (Wikipedia)
Official online Readline documentation

Bash tips II

2008-02-19T13:07:00.009+01:00

RETYPING A COMMAND YOU TYPED SEVERAL LINES BEFORE

Sometimes you have to type a command you typed before, but you don't want to write it again, or don't remember exactly what you wrote on your command prompt.
Solution is easy, we are gonna use reverse search!

Press the keys: ctrl+r and then type part of the command you want to retype.
NOTE:It is not necessary to write the beginning of the command, you can write whatever part you want for reverse search.

If reverse search has found a command but it is not the one you were searching for, type ctrl+r again till you find it, or write a better part of the command at search time.

Now we have found the command, we have two options:
- pressing enter, the command will be executed
- pressing tab key we will be able to edit this command at the bash prompt prior to its execution.

CHANGING INTO ANOTHER DIRECTORY but memorizing where we are now in order to return later easily

This is useful if you have long weird named paths.

We are now located at foo directory:

:/foo$pwd
/foo

We want to change into bar directory, instead of using cd command we use pushd
:/foo$pushd /bar

Now we are in /bar directory:

:/bar$pwd
/bar

In order to return to prior foo directory we only have to run popd command.
:/bar$popd

:foo$pwd
   /foo

CHECKING FOR BAD BLOCKS IN A PARTITION

Sometimes we want to check the blocks of a hard disk we have just bought, or whatever...

We have two options:

First time, when creating the filesystem with '-c' option

e.g: mkefs.ext3 -c -b 4096 -L foo /dev/sdb2

If the filesystem at this partition has been already created we can use badblocks command.

NOTE: Read carefully badblocks man page, $man badblocks before doing anything potentially harmfull.

e.g: sudo badblocks -v /dev/sdb2

TVAnts on Ubuntu

2007-09-02T11:29:00.006+02:00

TVAnts is a peer to peer program that allows you to share live streams instead of files.
Although these streams can contain any sort of media they are mostly used for watching live football matches and other events on PCs.

TVAnts pages:

www.tvants-ppstream.com
Official TVAnts page is written in chinese: tvants.com

Installing TVAnts:

Download TVAnts setup program: ( I have obtained this address from official TVAnts page.)
$wget http://88.191.73.231/~cali/tvants/TvantsSetup.exe

We need wine to run TVAnts setup program because it is a microsoft windows executable:
$sudo aptitude install wine # if you have not already installed wine program.
$wine "TvantsSetup.exe"

It will install itself, and then we will be able to exec the program:
$wine ~/.wine/drive_c/Program\ Files/TVAnts/Tvants.exe
or
$wine 'C:\Program Files\TVAnts\Tvants.exe'

Watching TV:

You will need at least one server at server tab.
e.g: list.tvants.com

At search tab you will be able to search for hundreds of channels.
Select some and add them to channel tab.

NOTE: Do not worry about error messages related to windows media player, we will use mplayer.

You can watch the channel you have selected runing in the console:
$mplayer -framedrop mms://localhost:16900/1
Last "1" means first channel from your selected channels list.
NOTE: Whenever you add a new channel this number increases in one, even if you delete previous unused channels.

NOTE: TVAnts is a peer to peer system so you should open 16800 port on your box to share streams you are watching with other users.

NOTE: You can also watch the tv streams using vlc instead of mplayer.

GRID Computing

2007-08-21T13:47:00.000+02:00

It looks fascinating!

Introduction to grid computing (IBM papers)

BOINC Distributed Computing Projects

2007-08-19T14:38:00.000+02:00

Donating spare CPU cycles to distributed computing projects.

Most of time your cpu load is well below under 100%.

You can check how many resources are you using right now, going to menu:
System --> Administration --> System Monitor

What about if this spare resources all over the world would be used by projects like curing diseases,
discover extraterrestrial inteligence, predice climate changes... ?

That is actually possible, here you have a list of projects you can participate:
http://boinc.berkeley.edu/projects.php

These are all distributed computing projects, based on BOINC platform.

Let's try this thing for real. First step will be installing BOINC:

BOINC - Debian and Ubuntu installation

$sudo aptitude update

$sudo aptitude install boinc-client boinc-manager

execute graphic boinc manager:
$boincmgr

you only have to follow wizard instructions.

NOTE: To join a project:
menu bar Tools -> Attach to project

NOTE: You will need konqueror browser to navigate the web from boincmgr.

Some info about interesting BOINC projects:

Roseta@home project: http://boinc.bakerlab.org/rosetta/

Rosetta@home needs your help to determine the 3-dimensional shapes of proteins in research that may ultimately lead to finding cures for some major human diseases. By running the Rosetta program on your computer while you don't need it you will help us speed up and extend our research in ways we couldn't possibly attempt without your help. You will also be helping our efforts at designing new proteins to fight diseases such as HIV, Malaria, Cancer, and Alzheimer's (See our Disease Related Research for more information). Please join us in our efforts! Rosetta@home is not for profit.

Climateprediction.net: http://climateprediction.net

Climateprediction.net is the largest experiment to try and produce a forecast of the climate in the 21st century. To do this, we need people around the world to give us time on their computers - time when they have their computers switched on, but are not using them to their full capacity.
[read more about the experiment]

Zattoo on Ubuntu Feisty

2007-08-12T14:22:00.000+02:00

Zattoo is a program that allows us to see streaming TV channels over Internet.

It is unfortunately closed source, but free as in free beer.

Let's go to official Zattoo web page: zattoo.com

Check on your language flag to see what channels are available to see at your zone.

Register to obtain zattoo program: http://zattoo.com/register

After registering, select linux and download zattoo deb file:
e.g: zattoo-2.2.10.6523-i386.deb

Now install the deb file:
$sudo dpkg -i zattoo-2.2.10.6523-i386.deb

I get dependency problems:
zattoo needs libgtkglext1 and libxul0d but those are not installed.

We install those required packages:
$sudo aptitude install libgtkglext1 libxul0d

Once dependencies are solved zattoo package configures automatically.
If that does not happen, then exec:
$sudo dpkg --configure zattoo

Download and install the Adobe Flash plugin from http://www.adobe.com if you have not it on your system yet.

run:
$zattoo_player

introduce your zattoo login (used when registering) and enjoy!

NOTE: To obtain new zattoo versions when they will be available, go to zattoo page, click on login word near country flags, and introduce your email and password.

NOTE: If you wanna know on which ports zattoo is listening, exec this command:
$sudo netstat -l -p -e | grep -i zattoo

Backup your system using TAR

2007-07-30T19:02:00.007+02:00

My system is a Debian Sid one (This article was first tested in an Ubuntu Feisty system)
Anyway this article is also useful in most other linux distros.

Tar tool allows us to make backups or even restore them, while our system is running.

It is a good idea becoming root to be able to access every file on the system, or at least you should use sudo command:

$sudo tar cvzpf /home/Backup.tgz --same-owner --exclude=/home/Backup.tgz --exclude=/home/error.log --exclude=/proc/* --exclude=/media/* --exclude=/dev/* --exclude=/mnt/* --exclude=/sys/* --exclude=/tmp/* / 2>/home/error.log

Tar options and arguments

c creates a tar backup
v activates verbose mode
z will compress data using gzip format
p preserves file permissions
f sends output to a file instead of standard output.

After f option it is necessary to write the file name where backup will be stored.
i.e: tar cvzpf /home/Backup.tgz is correct, but
tar cvzfp /home/Backup.tgz is wrong.

/home/Backup.tgz is our backup file name.

--same-owner preserve file ownership, it is not necessary because, being root, is a default option.

Excluding files from Backup

--exclude option gives us the possibility of excluding files and directories from backup.

--exclude=/home/Backup.tgz --exclude=/home/error.log Prevent Backup file and error log file to be stored.

--exclude=/proc/* --exclude=/dev/* --exclude=/sys/*

These are virtual directories so will not be stored.

NOTE: Difference between --exclude=/proc/* and --exclude=/proc is that first option would store a void proc directory, and second one would store nothing.

--exclude=/tmp/*

/tmp is a temporary directory, and is deleted on every boot, so will not be backed up either.

--exclude=/mnt/* --exclude=/media/*

If you want to save your main system only, and not what you have mounted on it, you should exclude these directories.

WHICH DIRECTORIES TO EXCLUDE?

To get some points about which directories do you need you could:

* Run mount or df commands, to know which filesystems and partitions are mounted in your system. e.g:
$ mount
$ df -h
* Read the Filesystem Hierarchy Standard (FHS) which tells you the meaning about most system and user directories.
* Read Linux System Directories and their Filesystems

NOTE: The easiest way to backup a system is booting from a live-cd or live-usb, then mount the partition you want to back up. This way you do not need to worry about which files to exclude, etc.

Logging errors

2>/home/error.log redirects standard error output to error.log file so we will be able to check if there have been important errors when creating backup file.

Normally some warnings appear about not storing some sockets and not including / at beginning of files. You can simply ignore them.

RESTORING YOUR SYSTEM

exec:
$sudo tar xvzf /home/Backup.tgz -C /

IF YOU RESTORE THE BACKUP IN A DIFFERENT PARTION OR MACHINE:
* Remember to change /etc/fstab file in your restored copy to correct new values.
* Also be sure, that the restored copy has all needed drivers for the new hardware.
* And in the end set correctly the bootloader configuration.

TESTING BACKUP FILE

To test if your backup file has no errors try this command:
$tar tvzf /home/Backup.tgz

BACKING UP VIA NETWORK

We are going to send our backup copy over the network. We will explain two methods:

* using netcat tool.
Bytes are sent without encryption.
No need of a previous server, we set it on the fly.

* using ssh tool.
It needs a ssh server already installed.
Provides encryption.
Simpler command setup.
It manages the connection.

We have two computers:

- Local computer with IP_local address. Contents of this computer will be backed up.
- Remote computer, which ip address is IP_remote. Backup file will be stored in this computer.

USING NETCAT TOOL

First at remote computer launch netcat in listening mode:
$nc -l -p 6000 >/home/Backup.tgz

That command starts listening at port 6000 and sends what receives to file /home/Backup.tgz.

Second at local computer:

$sudo tar cvzp --same-owner --exclude=/home/error.log --exclude=/proc/* --exclude=/media/* --exclude=/dev/* --exclude=/mnt/* --exclude=/sys/* --exclude=/tmp/* / 2>/home/error.log | nc -w 3 IP_remote 6000

NOTE: We have deleted f and --exclude=/home/Backup.tgz options because tar data is sent to standard output instead of to a file.

Backup starts, is sent via network and stored at remote computer.

NOTE: You need to start first netcat in listening mode or it will give you a connection error.

USING SSH TOOL

Depending on where is the ssh server installed we have two possibilities:

ssh server in remote computer: (We exec this command in the local computer)
$sudo tar cvzp --same-owner --exclude=/home/error.log --exclude=/proc/* --exclude=/media/* --exclude=/dev/* --exclude=/mnt/* --exclude=/sys/* --exclude=/tmp/* / 2>/home/error.log | ssh IP_remote "cat - > /home/Backup.tgz"

ssh server in local computer: (We exec this command in the remote computer)
$ssh IP_local "sudo tar cvzp --same-owner --exclude=/home/error.log --exclude=/proc/* --exclude=/media/* --exclude=/dev/* --exclude=/mnt/* --exclude=/sys/* --exclude=/tmp/* / 2>/home/error.log" > /home/Backup.tgz

More info at ubuntu forums:
BackupYourSystem using Tar
BackupYourSystem

Free software - open source LINKS

2007-07-29T21:52:00.001+02:00

DOCUMENTATION
The Linux Documentation Project
Linuxdocs - Linux Documents

KERNEL FOCUSED LINKS
KernelTrap
www.kernel.org
KernelNewbies.org

MAGAZINES
LinuxJournal

OTHER LINKS
Linuxsecurity.com
Debian-Administration.org
Linux From Scratch
Linux Networking Wiki
The Free Software Foundation

Errors and Solutions

2007-07-25T20:09:00.002+02:00

Solutions to common linux related errors appear frequently along this blog.
Unfortunately it is very difficult to track them from main page.

This blog entry shows a list of common errors and corresponding articles where solutions are explained.

"Could not open '/dev/kqemu' - QEMU acceleration layer not activated"

Installing Qemu on a Ubuntu Feisty System

"Could not open '\\.\kqemu' - QEMU acceleration layer not activated"

Installing Qemu on Windows Vista

"/dev/sdX does not have any corresponding BIOS drive"

Howto create a ubuntu usb live with persistence

Howto change X-Windows screen resolution

Bash tips

When booting GParted live cd, tft screen ends black

Resizing partitions with gparted

Network in Qemu does not work

Installing Qemu on a Ubuntu Feisty System

"apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName"

Installing and Configuring Mediawiki on a Ubuntu Gutsy Desktop System

Installing Qemu on a Ubunty Feisty System

2007-07-18T17:38:00.001+02:00

That simply command will install qemu emulator:
$sudo aptitude install qemu

Right now, qemu works as an emulator, that is, emulates every guest system instruction on the host system.
Emulating is a slow working mode, but if qemu runs on a x86 platform, it is possible to execute guest code directly as host code so speed will improve. (That is called virtualization)

INSTALLING KQEMU MODULE

To use virtualization mode in qemu, we have to install kqemu.

#aptitude install kqemu-common
That package has some documentation and a configuration file, but is not really kqemu module

$sudo aptitude install kqemu-source # Installs kqemu module sources

Compiling sources:

NOTE: You will need libc6-dev package to be able to compile kqemu sources.
If you haven't it: $sudo aptitude install libc6-dev

$sudo su # Becoming root

#cd /usr/src
# tar xvfj kqemu.tar.bz2 
#cd modules/kqemu
# ./configure
#make
#make install

kqemu module is now installed!!

Gonna load kqemu module:
#modprobe kqemu

and then run qemu:
#qemu -m 256 -cdrom .....

Appears an error:
"Could not open '/dev/kqemu' - QEMU acceleration layer not activated"

This bug occurs because qemu searchs for a module which major number equals zero and kqemu-common has set it to 250.

To solve that:

#rmmod kqemu
#gedit /etc/modprobe.d/kqemu

and change 250 by 0

again:

#modprobe kqemu
#qemu -m 256 -cdrom .......

SETTING THE NETWORK IN QEMU

If you dont specify network options when invoking qemu, then defaults apply.

This default options are: -net nic -net user
-net nic : emulates a NE2000 network interface card.
-net user: use the user mode network stack which requires no administrator priviledge to run.

That should be enough to have network working in your virtual machine but with some limitations:
* Pings are not available.
* By default User mode network stack allow us to navigate and connect to our host system, but not to act as a server.

User mode network stack has a built in dhcp server that will provide us an ip address.

If everything has gone fine you can open a browser and surf on the internet.

If you cannot connect to internet, open a console and type:
$ifconfig

check if virtual nic has its associated ip address and if not, exec this command:
$sudo dhclient eth0 # eth0 is your virtual nic

try your browser again.

NOTE: Another way to configure the network in qemu consists in using a tap device and a network software bridge, instead of using user mode network stack.

Apt, Aptitude and Dpkg Reference

2007-07-07T20:57:00.004+02:00

Apt, Aptitude and Dpkg are Debian package managing tools. Let's see a small reference about them:

# apt-get install foo .......................Installs foo package
# apt-get remove foo ........................Removes foo package
# apt-get remove --purge foo ................Removes foo package and its configuration files.
# apt-get update ............................Updates package database.
# apt-get -f install.........................Installs and removes packages in order to fix dependency problems.
# apt-get clean .............................Deletes all .deb packages from local repository.
# apt-get upgrade ...........................Upgrades all packages to its newer versions.
# apt-get dist-upgrade ......................Upgrades packages but also deals with dependency problems caused by new packages.
$ apt-get source foo ........................Downloads foo package source files.
# apt-get -t unstable foo ...................Installs foo package searching for foo package and its dependencies at unstable version.
# apt-get foo/unstable ......................Installs foo package from unstable version, but searchs for dependencies without overriding priorities at /etc/apt/preferences file.
# apt-get build-dep foo .....................Installs all necessary packages to satisfy the build dependencies for foo source package.

$ apt-cache show foo ........................Gives a long info description about foo package.
$ apt-cache search foo ......................Searchs for packages that match "foo" pattern.

# apt-file update ...........................Resynchronize the package contents from their sources (/etc/apt/sources.list)
$ apt-file search foo .......................Lists all packages containing files that match foo pattern. Searchs also in not installed packages.

# aptitude install foo ......................Installs foo package
# aptitude remove foo .......................Removes foo package
# aptitude remove --purge foo ...............Removes foo package and its configuration files.
$ aptitude search foo .......................Searchs for packages that match "foo" pattern
# aptitude update ...........................Updates package database.
# aptitude upgrade ..........................Upgrades packages to its newer versions.
# aptitude safe-upgrade .....................Same as aptitude upgrade.
# aptitude full-upgrade .....................Upgrades packages to its newer versions, taking care about dependencies. Sames as dist-upgrade.
# aptitude hold foo .........................Marks foo package so it will not be removed or upgraded when executing safe-upgrade or full-upgrade
# aptitude unhold foo .......................Turn off the hold on foo package.
$ aptitude show foo .........................Gives a long info description about foo package.
# aptitude clean ............................Removes all previously downloaded .deb files from the package cache directory.
$ aptitude download foo .....................Downloads foo package to current directory.

# dpkg -i foo ...............................Installs foo package
# dpkg -i --force-depends foo ...............Converts all dependency errors into warnings and installs foo package.
# dpkg -r foo ...............................Removes foo package
# dpkg --purge foo ..........................Removes foo package and its configuration files too.
$ dpkg -l *foo* .............................Lists packages containing "foo" pattern.
$ dpkg -L foo ...............................Lists files pertaining to foo package.
# dpkg-reconfigure -plow foo ................Reconfigures previously installed "foo" package, asking all configuration questions.
# dpkg --configure -a ...........................Configures all packages that have been unpacked but not yet configured.
$ dpkg --search foo .........................Lists packages containing files matching foo pattern. Only searchs on installed packages.
$ dpkg -c foo.deb ...........................List files contained in foo.deb package.
$ dpkg -I foo.deb ...........................Shows info about foo.deb package.

$ dpkg-query -S foo .........................Searchs for a filename from installed packages listed in the local dpkg database.

More info at:
The Debian package management tools.
APT Howto.
Debian package management.

Howto create an Ubuntu UsbLive with persistence

2007-07-07T18:49:00.000+02:00

First step is downloading Ubuntu Dapper iso file:

NOTE: Newer versions(Feisty and Gutsy), by now, july 2007, have a bug that prevents to use persistence feature.

You can navigate to Ubuntu download page and select Ubuntu 6.06 LTS Desktop edition (alias Dapper),

or simply enter at console command line:
$wget http://releases.ubuntu.com/dapper/ubuntu-6.06.1-desktop-i386.iso

I recommend a usb pendrive with a capacity higher than 1 Gigabyte, because you will need at least 700 megabytes to copy dapper iso file on it.
In my case I use a 2G pendrive.

Connect the usb pendrive so it be detected.

$dmesg command will show something like:

[ 2697.454838] usb-storage: device found at 4
...
[ 2704.387453] SCSI device sdh: 4029440 512-byte hdwr sectors (2063 MB)

$fdisk -l also shows the new device.

If you still dont find it, you can seek for it at $cat /proc/bus/usb/devices output.

On my system the new device appears as /dev/sdh, in this tutorial, to be more general, I will write it as /dev/sdX.

Next step will be partitionating our usb pendrive: (choose the program you prefer: fdisk, cfdisk, gparted ...)

#fdisk /dev/sdX

(for help on this step read $man fdisk)

I partitionate the device into two partitions sdX1 and sdX2, both sized one gigabyte, and make bootable the first one, showing this result with fdisk:

Device	Active	Beginning	End	Blocks	Id	System
/dev/sdX1	*	1	493	978081	b	W95 FAT32
/dev/sdX2		494	1015	1035648	83	Linux

Umount both partitions if they are mounted and then format them with:

#mkfs.vfat -F 32 -n usb /dev/sdX1
#mkfs.ext3 -L casper-rw -b 4096 /dev/sdX2

NOTE: casper-rw label is important, do not change it.

Mount dapper iso file in your harddisk:

#mkdir dapper_directory
#mount -o loop ubuntu-6.06.1-desktop-i386.iso dapper_directory

Copy iso files to first usb pendrive partition:

#mount /dev/sdX1 /media/foo
#cd dapper_directory
#cp -dpR . /media/foo

Installing grub bootloader:

#grub-install --root-directory=/media/foo /dev/sdX

this does not install menu.lst file so we will create it manually:
$sudo gedit /media/foo/boot/grub/menu.lst

Howto change isolinux.cfg entries (/media/foo/isolinux/isolinux.cfg) into menu.lst format:

E.g: isolinux.cfg entry

LABEL live
menu label ^Start or install Ubuntu
kernel /casper/vmlinuz
append   boot=casper initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw quiet splash --

changes into: (menu.lst entry)

title    Start or install Ubuntu
root     (hd0,0)

<---------------- this is necessary to identify usb device at boot.

kernel   /casper/vmlinuz boot=casper initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw quiet splash
initrd   /casper/initrd.gz
boot

NOTE: If you have problems creating menu.lst file, copy the one that appears at the end of this article.

Now you have written a correct menu.lst file at /media/foo/boot/grub directory exec again:
#grub-install --root-directory=/media/foo /dev/sdX

NOTE: If grub gives this error message "/dev/sdX does not have any corresponding BIOS drive"
execute this command:
#grub-install --root-directory=/media/foo --recheck /dev/sdX

NOTE: to be able to run your usb pendrive from qemu you have to trick the emulator giving a usb dapper iso as a cdrom device e.g:
#qemu -hda /dev/sdX -cdrom ubuntu-6.06.1-desktop-i386.iso -boot c

If you want to restart your computer to probe your creation, run:
#eject /dev/sdX

NOTE: eject /dev/sdX umounts sdX partitions and deletes /dev/sdX, /dev/sdX1,... devices

Restart and boot from your usb pendrive.

Have fun!!

APPENDIX: Example of menu.lst file

NOTE: persistent tag at first kernel line enables persistence mode in our usb pendrive.

timeout         10

color cyan/blue white/blue


title           Start Ubuntu in Persistent mode
root            (hd0,0)
kernel          /casper/vmlinuz boot=casper initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw persistent
initrd          /casper/initrd.gz
boot

title           Live - Start or install Ubuntu
root            (hd0,0)
kernel          /casper/vmlinuz boot=casper initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw
initrd          /casper/initrd.gz
boot

title           Start Ubuntu in safe graphics mode
root            (hd0,0)
kernel          /casper/vmlinuz boot=casper xforcevesa initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw
initrd          /casper/initrd.gz
boot

title           Check CD for defects
root            (hd0,0)
kernel          /casper/vmlinuz boot=casper integrity-check initrd=/casper/initrd.gz ramdisk_size=1048576 root=/dev/ram rw
initrd          /casper/initrd.gz
boot

title           Memory test
root            (hd0,0)
kernel          /install/mt86plus
boot

This article is based on this excelent spanish one extracted from Daniel Perella's Blog.

Xen

2007-06-26T21:41:00.000+02:00

Xen is a virtual machine monitor (VMM) for x86-compatible computers. Xen can securely execute multiple virtual machines, each running its own OS, on a single physical system with close-to-native performance.

Xen Wiki

Xen (Wikipedia)

Xen FAQ

howto-install-windows-xp-vista-on-xen

A brief introduction to xen-tools (debian-administration.org)

Installing Xen 3.0 upon Debian Sarge

Gentoo Linux Distribution

2007-06-26T08:49:00.001+02:00

Gentoo official page

Gentoo Linux Distribution (Wikipedia)

Gentoo Linux operating system is designed to be modular, portable, easy to maintain, flexible, and optimized for the user's machine. All tools and utilities are built from source code. For convenience, however, several large software packages are also available as precompiled binaries for various architectures via the Portage system.

It is a distro oriented to developers and network professionals. Gentoo at distrowatch

Gentoo Wiki

Packages Online Database.

INSTALLING

Downloading Gentoo

Installing Gentoo Handbook

Linux Gazette article about installing Gentoo

LIVE CD

HowTo build a LiveCD from scratch (Gentoo-Wiki)

IRC CHANNEL

#gentoo at irc.gnu.org

OTHER INTERESTING LINKS

Embedded Gentoo

Gentoo Development Guide

File types and Debian packages

2007-06-19T20:38:00.001+02:00

This article describes some file types (their extensions) and programs and debian or ubuntu packages to visualize those file types.

File Extension	Program	Debian/Ubuntu package	File Description
.chm	gnochm	gnochm	Microsoft help files
.djvu	djview	djview / djvulibre-plugin	Djvu file format for documents (alternative to pdf)
.rar	unrar	unrar	Rar compressed file format
.flv	mplayer	mplayer	Flash video file format

Ubuntu

2007-06-18T12:31:00.000+02:00

Ubuntu Community FAQ

Ubuntu FAQ

Repository Components

Ubuntu Packages

Mark Suttleworth wiki

Mark Shuttleworth's blog

Ubuntu Forums

HowTo: Install Feisty on a bootable USB Flash drive

Ubuntu USB live

Persistence Bug Feisty

Get involved in Ubuntu

Becoming an Ubuntu Developer

Ubuntu development

Ubuntu paid work

Ubuntu bug tracker

Gutsy Release Schedule

Gutsy Tribe-1 CDs

Live Usb Pendrive Persistent

IRC CHANNELS

(at irc.gnu.org)
#ubuntu
#ubuntu+1

Bash tips

2007-06-17T17:14:00.001+02:00

http://builder.com.com/5100-6372_14-5827311.html

Customizing the bash command prompt

COMMAND REFERENCE

Linux Command Reference Index

Another command Reference

O'Reilly Command Reference

GNU/Linux Command Line Tools Sumary

Learning the Shell Tutorial

Changing X resolution

$xrandr #shows all available resolutions
i.e:

SZ:    Pixels          Physical       Refresh
*0   1024 x 768    ( 271mm x 203mm )  *61
 1    800 x 600    ( 271mm x 203mm )   73
 2    640 x 480    ( 271mm x 203mm )   73

now, to switch to 800x600 resolution we can exec:

$xrandr -s 1

or

$xrandr --size 800x600

wait for 5 secs and voila! resolution changed!

NOTE: another way to change resolution is pressing ctrl+alt++ or ctrl+alt+- keys

NOTE: this command is very useful to change qemu X-windows resolution when it is bigger than your screen.

Listing file sizes in human readable form:

ls -l # shows file sizes, usually in bytes.

if you want to list them in a more readable way type:

ls -lh

NOTE: this "h" switch option also works with other commands like df, du, etc.

Obtaining an ISO file from a CDRom

You need to now what device your cdrom drive is associated to: (In this example will be /dev/sdX)

exec this command:
dd if=/dev/sdX of=cdrom_image.iso bs=1000000

that makes a byte by byte copy from /dev/sdX device (our cdrom) to cdrom_image.iso file in 1000000 bytes size chunks.

NOTE: Change bs argument to suit your needs. That value has effect on the speed the copy is performed.

Resizing partitions with GParted

2007-06-12T17:05:00.000+02:00

GParted stands for Gnome Partition Editor

GParted is an industrial-strength package for creating, destroying, resizing, moving, checking and copying partitions, and the filesystems on them. This is useful for creating space for new operating systems, reorganizing disk usage, copying data residing on hard disks and mirroring one partition with another (disk imaging).

Supported Filesystems

Before using GParted we should check if it supports the filesystems we want to deal with:
Filesystems supported

More info about filesystems from Wikipedia.

Getting GParted

GParted is distributed within three ways, as source code, as live cd or as live usb.

I choose to download and use the live cdrom one: GParted Live CD.

So I download and burn it to a writable cd, and then boot my computer from this cdrom.

NOTE: When booting GParted live cd, my tft screen ends black. To solve that, press ctrl+alt+del. Then at console mode exec #Forcevideo and select a supported vesa video mode for the tft.

Installing Qemu on Windows Vista

2007-06-10T22:21:00.000+02:00

Qemu introduction from Wikipedia

QEMU emulates a full computer system, including a processor and various peripherals. It can be used to provide virtual hosting of several virtual computers on a single computer.

Accelerator
Qemu author, Fabrice Bellard, also wrote a Linux kernel module (with preliminary ports to FreeBSD and Windows) named KQEMU or QEMU Accelerator, which notably speeds up i386 emulation on i386 platforms. This is accomplished by running user mode code directly on the host computer's CPU, and using processor and peripheral emulation only for kernel mode and real mode code. KQEMU also supports a kernel emulation mode in which portions of kernel mode code run on the host's CPU

Qemu official page:
http://fabrice.bellard.free.fr/qemu/

Qemu ported to Windows:
http://www.h7.dion.ne.jp/~qemu-win/

First we download a zip package:
qemu-0.9.0-windows.zip

Next unzip archives to a folder.

There are some clues at file README-en.txt, and a html manual at qemu-doc.html.

Qemu is now ready to be run:
so exec qemu-win.bat and a small linux test image "linux.img" is emulated.

NOTE: When a mouse cursor is missing, type Ctrl and Alt key together. Please use Alt
and Tab on WindowsMe.

NOTE: To exit from Linux, press Ctrl-Alt-2 keys together then you will see (qemu) prompt.

Then type quit: (qemu) quit

Running Qemu:

I have downloaded a Ubuntu iso cdrom image: ubuntu-7.04-desktop-i386.iso

First I exec C:\Windows\System32\cmd.exe to open a comand line window, and then:
>cd <qemu-directory-path> >qemu -L . -m 512 -cdrom ubuntu-7.04-desktop-i386.iso

Argument options have the following meanings:
Option	Value	Explanation
-L	bios path	in our example actual directory "."
-m	available memory	Default is 128 meg, I set it to 512
-cdrom	iso cdrom image path	Iso image to emulate a cdrom

Qemu gives this warning:
Could not open '\\.\kqemu' - QEMU acceleration layer not activated

To avoid this message, install qemu accelerator, which will improve qemu speed:
(NOTE: uninstall any previous version accelerator you have before installing this one)
Qemu accelerator Kqemu-1.3.0pre11

NETWORK SET UP FOR QEMU ON WINDOWS VISTA

Right now we don't have network available. We check at this doc for some clues: HowToNetwork-en.html

I have decided to use a TAP (virtual ethernet network interface) to have full internet access: TapWin32-en.html

First we need a VPN driver for windows: OpenVPN driver download page.
Download and install this program: openvpn-2.0.9-install.exe

Once installed go to Programs menu and then
-> OpenVPN -> Add a new TAP-Win32 virtual ethernet adapter

If all has gone fine, a tap device will appear at:

Control panel -> Network and Sharing Center -> Manage networks

Remember the TAP interface name because it will be passed as an argument to qemu, i.e. in my computer is "Local area connection 2"

Now we have to establish a NETWORK SOFTWARE BRIDGE in windows vista.

Network bridge (Wikipedia)

A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model.
In our case the bridge will interconnect a real network interface with our TAP interface at data link layer, so both interfaces will share same IP address.

Howto set up a network bridge at windows xp and vista: Win XP network bridge set up.

Select both interfaces pressing ctrl key, and right click the mouse.
Select "Bridge connections" at the pop up menu and wait till network bridge will be completed.

After bridge completion gonna set up its network configuration:
right click at bridge icon -> properties -> Internet protocol version 4

If you have a dhcp server you can set bridge interface to automatically get its IP address.

I use a static network configuration at my LAN.

(change values to suit your network.)
IP 192.168.0.5 netmask 255.255.255.0 gateway 192.168.0.129 DNS1 194.179.1.100 DNS2 194.179.1.101

To check the network at console window we can make some pings:

ping 192.168.0.5
ping 192.168.0.129 (checking gateway)

Time of truth arrives, we launch qemu:

qemu -L . -m 512 -cdrom ubuntu-7.04-desktop-i386.iso -net nic -net tap,ifname="Local area connection 2"

at ubuntu guest system I configure the network with a free IP address on my LAN:

IP 192.168.0.10
netmask 255.255.255.0
gateway 192.168.0.129
DNS 194.179...

pings work:
ping 192.168.0.10
ping 192.168.0.5
ping 192.168.0.129 (checking the gateway)

If you have Internet access through your LAN, you can now open a browser and surf on the Internet from inside your qemu guest system. :-)

More info about bridging:
hnw_bridge_install
hnw_understanding_bridge

OTHER INTERESTING LINKS

Qemu HowTo Floppy Cdrom

Debian GNU/Linux Distribution

2007-06-08T23:54:00.003+02:00

Debian GNU/Linux is an complete Operating System based on the Linux kernel(there are also other platforms available).

It is developed in an open way by volunteers all over the world.

Debian (from Wikipedia)

DEBIAN DISTRIBUTION PHILOSOPHY AND GOALS

These documents describe Debian philosophy.

Debian Manifiesto
Debian Social Contract - Describes Debian Goals.
Debian Free Software Guidelines - Requirements software has to accomplish to be accepted as Debian Free Software.

Debian currently provides over 26000 software packages, and targets eleven hardware architectures.

Ubuntu distro and others like Damn Small Linux, Knoppix, Xandros, etc are Debian based distributions.

DEVELOPMENT PROCEDURE

Debian has three main branches: unstable (sid), testing and stable.

The stable one is suited for server environments. Packages at this version are frozen, and there are only security updates. (Debian Security Faq)

Usually newer software package versions are added to the unstable branch. If no serious bugs are found, after some time, the package migrate to testing branch (its dependencies also have to be in the testing branch).

Stable branch regularly receive security updates. Using Debian Sid (unstable) means that you have the latest package versions at the cost of stability and security.

Debian repositories are separated into several categories:

main

contrib

non-free

DEBIAN PACKAGE MANAGEMENT SYSTEM

APT (Advanced Packaging Tool) is the Debian Package Management System. It is a user interface to some libraries that deal with software installation.

It comprises a set of tools. e.g: apt-get, apt-cache, apt-cdrom, ...

APT tracks dependency problems, performing installation and removing of packages in the most suitable order. When you install a package APT automatically installs all required dependencies. APT allows installing packages via network.

Apt, Aptitude, Dpkg Reference Article.

DEBIAN PACKAGE DEVELOPMENT

Documentation about creating and maintaining Debian packages.

Developer manuals

Debian New Mantainers' Guide

OTHER DEBIAN RELATED LINKS

Debian Wiki

Debian Reference (debian.org)

Debian FAQ

Getting support for Debian GNU/Linux.

Debian package list

Debian Forums

Debian Administration

IRC

#debian irc channel at irc.gnu.org server.

Comparison of Linux distributions

2007-05-20T01:18:00.000+02:00

Wikipedia: Comparison of Linux distributions.

Each Distro has a package managing system, and uses a package format, i.e:

deb for Debian,
rpm for Fedora(Red Hat),
tgz for Slackware,
...

LiveDistro List

2007-05-19T14:31:00.000+02:00

Easiest way to begin with Linux based systems is using a Live CD or Live USB distribution.

LiveDistro is a generic term for an operating system distribution that is executed upon boot, without previous installation on a hard drive. In fact, a hard drive is not needed at all.

What in other distros would be stored in hard disk, is stored in RAM memory. That cuts down on the RAM available to applications, reducing performance somewhat. (Is recommended a minimum of 256 MB RAM)

For a list of LiveDistros you can search at:

List of LiveDistros

Comparison of Linux LiveDistros

www.livecdlist.com

I have tested Ubuntu and Knoppix.

Other insteresting links:

Linux Live Scripts How to build your own LiveDistro.
HOWTO build a LiveCD from scratch (gentoo-wiki).