Linux Boot Process

-


When we press the power button of computer which has Linux Operating system, and after few minutes Linux Login prompt comes.
We wonder that how it happens behind the screen. Let’s simplify Linux OS Booting process.
1)    BIOS – Basic Input Output System
*      Checks system integrity
*      Looks for boot loader program at cdrom / flopy / harddisk
*      Have a facility to change booting parameter via F12/Del/F2 as per the system
*      Load the boot loader and transfers control to it
Summary:  It goes with first boot options and provides control to MBR (Master Boot Record)
2)    MBR – Master Boot Record
*      Situated into first sector of bootable disk . example - /dev/sda ,  /dev/sdb,  /dev/hda       
*      It has information about boot loader ( GRUB / LILO )
*      Its size is less than 512 bytes and having 3 components
o   Primary Boot Loader Information
o   Mbr validation check
o   OS partition table information
 Summary: It executes GRUB (GRand Unified Boot loader).
3)    GRUB – GRand Unified Boot Loader
*      You can decide which kernel should be booted from multiple installed kernel versions.
*      Run splash image for specified interval time as per config file
*      It has understanding of file system
*      Grub.conf


4)    Kernel
*      Responsible for mounting the root file system
*      Executes INIT program
*      INIT is the first program to be executed by kernel and its PID is 1.
*      Initrd stands for initial RAM disk
*      Initrd has necessary driver information and other information which is required to mount file system until kernel booted , it stands as temporary root file system
5)     Init
*      Run configured run level as per inittab file
*      We can also change run level at boot time by define specific run level
*      Available Different Run Levels
0        HALT
1        Single User Mode
2        Multiuse without networking
3        Console Based Multiuser mode – but no GUI.
4        Not defined
5        GUI based Multiuser mode
6        Reboot
6)     Run Level
*      While OS is booting up, we can see various services coming up and getting status.
*      It happens due to configuration of those services in that specific run level
*      Various programs are in run level directory which has initial word S or K.
*      S stands for startup and K stands for Kill.

Comments

Post a Comment

Popular posts from this blog

PROCEDURE TO CREATE AN ANIMATION TO REPRESENT THE GROWING MOON.

-
Image
1.       Open flash 8 software -> click on flash document ->go to windows->properties ->select the properties tool-> choose the Background to black. 2.       Go to fill color under tool bar-> select the white color. 3.       Select the oval tool in order to draw the moon. u will get a white circle. 4.       Select the oval tool in order to draw the moon. u will get a white circle. 5.       Select the white circle on the worksheet using the selection tool ->right click- >convert to symbol ->select movie clip ->give suitable name e g: moon->click ok. 6.       Go to filter ->click on the + symbol->select glow to apply glowing effect-> select the color to white under glow and adjust the blur x/blur y values. 7.       Click on the...
Read more

PROCEDURE TO CREATE AN ANIMATION TO INDICATE A BALL BOUNCING ON STEPS.

-
Image
1.     Go to start- macromedia- click on flash document 2.     Select the line tool and draw the steps. color it using the paint bucket tool 3.     Select the circle from the tool bar and create a circle on the work area. 4.     Now fill the color to the circle using the paint bucket tool from the tool bar. 5.     Go to frames right click on the first frame and choose insert key frame. Slightly move the ball. Repeat the same procedure by adding new key frames to show the ball change the shape of the ball slightly when it touches the surface. 6.     In order to change the shape use the free transform tool. 7.     Go to control and click on test movies .you will observe the ball bouncing on steps.
Read more

PROCEDURE TO SIMULATE MOVEMENT OF A CLOUD.

-
Image
1.       go to start- macromedia- click on flash document 2.       create a blue background in layer 1 3.       Now insert a layer 2 and draw the clouds in this layer. 4.       in order to create the clouds, go to tool bar and select pencil option, draw the cloud in layer2 5.       fill the color to the cloud, right click on it- choose convert to symbol option- give the name as cloud 6.       select the movie clip option and click ok. 7.       Go to filter ->click on the + symbol->select glow to apply glowing effect-> select the colour to white 8.       under glow and adjust the blur x/blur y values. 9.       give the appropriate blur effect to the cloud. 10.   go to frames, insert key frame on both ...
Read more