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Archive for July, 2009

When your Linux Lock

Posted by aboelnour on July 31, 2009


blue_lock main

Peace be upon you:

How many times your system stop working suddenly?

sure a lot in windows and you will use the ALT+CTRL+DELETE to kill any harm process.

so there is any alternative way in linux?

linux rarely stop working and any harm process don’t give you a response Linux make a force quit to it

but… what can i do if the all system don’t give me a response ?

As i said ” linux rarely stop working ”  but may be there is an error with your GUI  – linux Separated between code and GUI Reverse Window$ if GUI fall all system fall – so what’s the solution?

press ALT+CTRL+F1

And run :

       

/etc/init.d/kdm restart

or

/etc/init.d/gdm restart

to restart your desktop environment .

#1 for KDA  And #2 for GNOME.

but what if it doesn’t work ? should i press the RESTART button?

No, there is a magic button call SysRq this button also called print Screen on your key bored

first you must know if your kernel support this button

run in terminal:

grep CONFIG_MAGIC_SYSRQ /boot/config-`uname -r`

if the answer was

CONFIG_MAGIC_SYSRQ=y

so your kernel support this button so you can follow

How to use this button?

Alt + SysRyq + button

Button is one of this options:

k : to kill any process

r : to reset your keybored

s : to Synchronize your hard disk (save any data in the buffer)

e : finish all process

i : finish all programs which hasn’t finished yet

u : make all your mounted devices READ-ONLY

b : restart your computer (last option)

o : shut down your computer

p : show an information about your processor

======

By the way how many one type his password in the login window and it didn’t written because the Numlock button is switched off ?!

here is the solution

run in terminal

sudo apt-get install numlockx

then run

gksudo gedit /etc/gdm/Init/Default

then add in the open file this:

if [ -x /usr/bin/numlockx ]; then

/usr/bin/numlockx on

fi

so the file will be on this form after editing in it :

#!/bin/sh

# Stolen from the debian kdm setup, aren’t I sneaky

# Plus a lot of fun stuff added

#  -George

if [ -x /usr/bin/numlockx ]; then

/usr/bin/numlockx on

fi

PATH=/usr/bin/X11:/usr/X11R6/bin:/opt/X11R6/bin:$PATH

OLD_IFS=$IFS

save , exit , restart your computer and see the result

so that’s it any feedback is welcomed

regards,

aboelnour

Posted in linux | Tagged: , , | Leave a Comment »

How Your Computer Boot?

Posted by aboelnour on July 30, 2009


boot

Peace be upon you:

How are you? in this article we will talk about the BOOT operation on your computer so read and enjoy 🙂

==========

History :
~~~~~~~~~~~~~~~~~~~~

* The Computer word boot is short for “bootstrap” (short for ‘bootstrap load”)

* The term bootstrap began as a metaphor derived from pull straps sewn onto the backs of leather boots with which a person could
pull on their boots without outside help

* In 1950’s when you press a bootstrap button caused a hardwired program to read a bootstrap program from apunched card
and then execute the loaded boot program which load ed a larger system of programs from a punched cards into memory ,
without further help from the human operator
so this word has been used at least 1958

Introduction :
~~~~~~~~~~~~~~~~~~~~

* A computer’s central processor can only execute program code found in Read-Only Memory (ROM) and Random Access Memory (RAM).
Modern operating systems and application program code and data are stored on nonvolatile data storage devices, such as hard disk drives,
CD, DVD, USB flash drive, and floppy disk. When a computer is first powered on, it does not have an operating system in ROM or RAM.
The computer must initially execute a small program stored in ROM along with the bare minimum of data needed to access the nonvolatile
evices from which the operating system programs and data are loaded into RAM.

* The small program that starts this sequence of loading into RAM, is known as a bootstrap loader, bootstrap or boot loader.
This small boot loader program’s only job is to load other data and programs which are then executed from RAM. Often,
multiple-stage boot loaders are used, during which several programs of increasing complexity sequentially load one after the other in a
process of chain loading.

Second-stage boot loader :
~~~~~~~~~~~~~~~~~~~~

* The small program which loaded is most often not itself an operating system, but only a second-stage boot loader, such as GRUB, BOOTMGR, LILO or NTLDR.
It will then be able to load the operating system properly, and finally transfer execution to it. The system will initialize itself, and may load device
drivers and other programs that are needed for the normal operation of the OS.

* Many bootloaders (like GRUB, BOOTMGR, LILO, and NTLDR) can be configured to give the user multiple booting choices. These choices can include
different operating systems (for dual or multi-booting from different partitions or drives), different kernel versions of the same operating system
(in case a new version has unexpected problems), different kernel options (e.g., booting into a rescue or safe mode) or some standalone program that can
function without an operating system, such as memory testers (e.g., memtest86+) or even games.[9] Usually a default choice is preselected with a time delay
during which you can press a key to change the choice, after which the default choice is automatically run, so normal booting can occur without interaction.

* The boot process is considered complete when the computer is ready to interact with the user, or the operating system is capable of running ordinary
applications. Typical modern PCs boot in about one minute (of which about 15 seconds are taken by a power-on self test (POST) and a preliminary boot loader
, and the rest by loading the operating system, pre-OS time can be considerably shortened by bringing the system with all cores at once, as with coreboot[10]
in as little as 3 seconds[11]; whereas, large servers may take several minutes to boot and start all their services.

Boot device :
~~~~~~~~~~~~~~~~~~~~

* The boot device is the device from which the operating system is loaded. A modern PC BIOS supports booting from various devices,
typically a local hard disk drive (or one of several partitions on such a disk), an optical disc drive, a USB device
(flash drive, hard disk drive, optical disc drive, etc.), or a network interface card (using PXE). Older, less common bootable devices include
floppy disk drives, SCSI devices, Zip drives, and LS-120 drives.

* Typically, the BIOS will allow the user to configure a boot order. If the boot order is set to “firstly, the DVD drive; secondly, the hard disk drive”,
then the BIOS will try to boot from the DVD drive, and if this fails (e.g. because there is no DVD in the drive), it will try to boot from the local hard drive.

Booting Sequence  :
~~~~~~~~~~~~~~~~~~~~

* Upon starting CPU runs the instruction located at the memory location  of the BIOS It typically contains a jump instruction that transfers
execution to the location of the BIOS start-up program. This program runs a power-on self test (POST) to check and initialize required devices.
The BIOS goes through a pre-configured list of non-volatile storage devices (“boot device sequence”) until it finds one that is bootable.
A bootable device is defined as one that can be read from, and the last two bytes of the first sector contain the word 0xAA55 (also known as the boot signature).

* Once the BIOS has found a bootable device it loads the boot sector and transfers execution to the boot code.
In the case of a hard disk, this is referred to as the master boot record (MBR) and is often not operating system specific The conventional MBR code
checks the MBR’s partition table for a partition set as bootable (the one with active flag set)[12]. If an active partition is found, the MBR code loads
the boot sector code from that partition and executes it. The boot sector is often operating system specific, however in most operating systems its main
function is to load and execute the operating system kernel, which continues startup. If there is no active partition, or the active partition’s boot sector is invalid,
the MBR may load a secondary boot loader which will select a partition (often via user input) and load its boot sector, which usually loads the corresponding operating system kernel.

Rebooting  :
~~~~~~~~~~~~~~~~~~~~
Hard reboot :

A hard reboot is when power to a computer is cycled (turned off and then on) or a special reset signal to the processor is triggered. This restarts the
computer without first performing any shut-down procedure. (With many operating systems, especially those using disk caches, after a hard reboot the
filesystem may be in an “unclean” state, and an automatic scan of on-disk filesystem structures will be done before normal operation can begin.)

Soft reboot :

A soft reboot is restarting a computer under software control, without removing power or (directly) triggering a reset line. It usually,
though not always, refers to an orderly shutdown and restarting of the machine.
This kind of reboot will not usually reset the hard disks, so that they have time to update their write cache to permanent storage.
Hard disks will also keep their configuration (like C/H/S adjustments, HPA, DCO, internal passwords…) over these reboots.

==========

For the old days take this one 😀

AwardBIOS_startup

so that’s the end for now any feed back are welcomed

best wishes,

aboelnour

Posted in general | Leave a Comment »

Linux Directory Structure

Posted by aboelnour on July 11, 2009


linux-penguin-big_origpreview-252x300

Peace be upon you:

so for any new user in linux come from windows the first thing he will notice  the file system structure is Radically different so this article aimed to make the things more Clearly to begin dealing with the  Linux Directory Structure so enjoy 🙂

————

>>> “/ “ :

The root directory is the starting point of your Linux file system. All other directories on your system exist in the root directory.

we need to differentiate between expressions :

1) root directory or root filesystem: this directory contains the all folders and files on your system like the C drive on windows

2) root account: like the Admin account in windows

3) root home: a private folder for the root

————

>>> “/bin, /usr/bin”:

This is the location where you find program files (binaries) accessible to all users.These are essential binaries that must be available at all times.

The /bin directory contains the most important programs that the system needs to operate.

/usr/bin contains applications for the system’s users. However, in some cases it really doesn’t make much difference if you put the program in /bin or /usr/bin.

————

>>> “/sbin, /usr/sbin“:

In this directory you will find binaries for the system administrator.

In many cases you must run these programs as the root account.

————

>>> “/boot“:

This directory contains everything you need to boot your PC

this is where the Linux kernel is kept. you’ll see a file called vmlinuz – that’s the kernel.

————

>>> “/dev“:

This directory contains all  devices that are available to a Linux system!!! HOW!!?.

in Linux, devices are treated like files and you can read and write devices like they were files. For example,/dev/fd0 is your first floppy drive, /dev/cdrom is your CD drive, /dev/sda is your hard disk

————

>>> “/etc“:

This directory contains the configuration files for the Linux system

These text files are kept in the directory /etc. In this directory, you will find
some important configuration files like /etc/passwd, which contains the database of local Linux users.

————

>>> “/home“:

This directory contains the personal files of a user are stored in his or her home directory.

————

>>> “/lib“:

This directory contains the shared libraries for programs that are dynamically linked. The shared libraries are similar to DLL’s on Winblows.

————

>>> “/media“:

This directory contains all mounted devices on your PC.

The different storage devices must be attached to some directory in the file system tree before they can be accessed.

————

>>> “/mnt“:

was the default directory for mounting devices. On more recent systems, this has been replaced by the /media directory.

————

>>> “/usr“:

This directory is probably the largest directory on your system. Here you can find almost all user-accessible files. Some people like to compare it to the programe files on windows .

This directory contains user applications and a variety of other things for them, like their source codes, or config files.

————

>>> ‘/opt‘:

This directory contains the large software installations and the big applications like the the OpenOffice suite, the Oracle database or the xampp 😀

————

>>> “/proc“:

this directory is a virtual folder it contains some info about the kernel itself. containg alot of info about your PC for more explanation

run in terminal : cat /proc/cpuinfo

you will see an info about your CPU

————

>>> “/root“:

this is the root account home folder that you will take control of it when you be a root account

————

>>> “/srv“:

If you were to run, say, an Apache web server on your computer, this is the directory you would put your HTML files

————

>>> “/sys“:

This directory can be used to store information about the state of your system. Its
use is like the use of /proc, with the difference that the information in /sys is kept on the hard disk.

————

>>> “/tmp“:

Programs can write their temporary files here.

————

>>> “/var“:

contain most of System variables

for more explanation

run in terminal : echo $USER

the result is your username so when you log in to your system the OS fill  some variables for you you can add a variable and give it a value for specified users .

————

for more information Run in Terminal :

man hier

linux-dir-tree

so that’s it thanks for reading and any feedback is welcomed.

best wishes,

aboelnour 🙂

/sbin, /usr/sbin

Posted in linux | 4 Comments »

 
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