Understanding rc file.

Name:
rc

Location:

/etc/rc.d/rc

Purpose:

This file is responsible for starting/stopping services when the run level changes.

Who initiate the script

Init initiates the script whenever a change in run level happen using init command.

Linux Boot Process for Beginners.

There are various articles available on internet explaining boot process.This is yet another attempt to reinvent the wheel but this time I m taking in consideration newbies, who just started loving Linux.


Most of the Articles on Linux Boot Process begins with the Power On stage ,I will change the trend by Beginning with Linux Installation.

Linux Installer (Anaconda) takes care of the Linux installation process.During the installation process It places a tiny file in the Beginning of the Harddisk.
(To be very specific Cylinder 0,Head 0 ,Sector 1 of the harddisk .You dont need to remember all this as you just started learning Linux but Little bit of extra details makes no Harm).

So Anaconda places a tiny file at a start of the Harddisk.

Now the question is why does he do that ?

Ans : As you go ahead you will understand the reason why.

What is the name of the file ?

Ans : In older Linux Distributions There was a file called LILO .but in modern Distributions of Linux the file is replaced by another file called GRUB.
Moral of the story : GRUB is Latest ,LILO is Old.

What does this file contains ?

This file contains reference to other files.

Why does it Contains the reference ?

Now this is interesting.

Mumbai Mantralaya Burning.

I was passing by a street and suddenly heard people telling mantralaya is on burn.

I checked the news and its was indeed burning....
May god help whoever trapped inside.


Lets talk some technology here.

Some guy updated his facebook saying "Mantralaya on burn i can see it". I m amazed by the speed such news spreads.Facebook and twitter are faster than So called news channels.

As this blog is sponsored by google you can view it on first page of google.

There are people who use such events to advertise .I know its sad but its another way to advertise.Be it India win the wordcup or  sad demise of a President .
At the end of the day Its all about advertising .

Disk ,Cylinders and Sectors

Disk is composed of cylinders.

Each cylinder is composed of disk sectors.Different Drives have different number of sector sizes.
For example
if a hard disk of Samsung has 2000 cylinder each of which consist of 16000 sectors .
Each sector size is 512 byte.
There fore the size of one cylinder is

16000 * 512 byte =16000 * 1/2 kb (as 512byte is a half kilobyte)= 8000 k = 8 Mb (approx).

There for the size of hard disk is 8 Mb* 2000 =16000 Mb = 16 Gb.

The more the size of cylinder the more the disk performance.For example Samsung disk with one cylinder size 8 Mb will give better performance than Western Digital of 4mb per cylinder size.

Interesting facts about Linux.

1) Swap is better pronounced as swop.The word has its origins in french.

2) Linux will only be installed to primary master.

3) Name of linux installer is called anaconda and
For Linux installation using GUI,the partitioning tool used is Druid.
Never ever use Druid to partition using Druid as it has problem of jumping the partition number.Better use Ctr+Alt+F2 when it ask for partitioning .It will switch to command mode then use fdisk command to partition the disk.Once you finish the partition use Ctr+Alt+F7 to come back to GUI installation.

4) There are no installation types they are better called as installation classes.

Installation classes are mainly catagorised in 4 parts.
1) Personal Desktop
2) Workstation
3) Server
4) Custom

The first and second class will not format the partition and will boot in GUI.
However the third class Server class will format the partitions and will boot in command line.

OSI layer simplified.

I always had problem remembering OSI layers so i just googled hoping i get something.

Whoolaaa , I got it

"Please do not throw sausage pizza away"
Away - Application
pizza - Presentation
sausage - Session
throw - Transport
not - Network
do - Data link layer
please - Physical.


All credit goes to original inventor .

Netstat linux command

netstat command is used to obtain network related information.

Such as
Routing table
Port information
Network interface information

let us explore netstat one by one.

1) How to display Routing table in linux?
2) How to find the port of particular application?
3) How Find out number of Machines (IP address) connected to Linux Server?

1) How to display Routing table in linux.

You can use netstat command to display routing table in linux.

#netstat -r