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Linux Booting Process in Telugu Part 5 | Linux Tutorial for beginners

3 min read



Linux booting:
————-
It is a process to initiate a laptop or desktop with os.
– when you press the power button then internally some process is going so, that is known as booting process.
– booting process is follows some steps internally. below are the steps

1 — Bios — basic input & output
post (power on self test)
hardware ram,rom,cd-rom
2 — MBR — boot recorder
3 — GRUB — grand united boot loader
4 — Kernal — taker care of os into Ram
5 — INIT process
0 halt
1 single usermode
2 multiuser
3 full multiuser mode
4 unused
5 graphical mode
6 reboot
6 — run level — /etc/rc.d/rco.d or rc1.d

1)BIOS:
——
– the first stage of booting process when you on/restart your machine the power is supplied to SMPS which converts AC to DC.
– the DC power is supplied to all device connected to that machine such as processor, RAM, CD-ROM, mouse, keyboard, etc..
– The most intelligent device in computer is processor(CPU).
– when power supplied it will start running it’s sequence of instructions stored in the memory.
– The instruction it will run is to pass control to BIOS
– in BIOS 2 operations are going
a)POST (power on self test)
b)selecting first boot device
– post is process of checking H/W availability.
– BIOS will have list of all devices.
– In post process it will send an electric pulse to each and every device.
– if an electric pulse is returned from that device it conclude the h/w working fine and ready for use it.
– if it does not receive signal from that device. it will treat that device is not working.

2)MBR:
—–
– The MBR is the first sector of the computer hard drive that tells the computer how to load the operating system, how the hard drive is partitioned.
– A master boot record (MBR) is the 512-byte boot sector that is the first sector of a partitioned data storage device of a hard disk.

3)GRUB:
——
– It is a multi boot loader package. that supports multiple operating systems on a computer. During boot-up, the user can select the operating system to run. if you are not specified it loads the default kernel.

4)KERNEL:
——–
– kernel is the core part of the operating system. once control is given to kernel which is the control part of all your OS & act as a mediator between h/w & s/w.
– kernel once loaded into RAM it always resides on RAM until the machine is shutdown.
– once the kernel start it’s operates the first thing it do is executing INIT Process.

5)INIT:
——
– after OS started initial process is starting. it is parent process of the all processes in Os.
– in “/etc/inittab” in this config file we have the default initialize process is their.
– It is the first process to start when a computer boots up, and it runs until the system shuts down
0 halt
1 single usermode
2 multiuser
3 full multiuser mode
4 unused
5 graphical mode
6 reboot

6)RUN LEVEL:
————
– when the linux system is bootup, you might see various services getting started.
– those are run level programs, executed from run level directory as defined by your runlevel
– depending on your INIT level settings, the system executed the program from one of the following directions.

Runlevel 0- /etc/rc.d/rc0.d/
1- /etc/rc.d/rc1.d/
2- /etc/rc.d/rc3.d/
3- /etc/rc.d/rc3.d/
4- /etc/rc.d/rc4.d/
5- /etc/rc.d/rc5.d/
6- /etc/rc.d/rc6.d/

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