Friends welcome back in this lesson we can learn about Linux boot process in detail.
So what is that process.
When we powered on our computer then after a few minutes we get the log in prompt.
OK.
So the process in Word in between when the power on the button do until we get the logon prompt is called
as the boot process.
So here in this lesson I would like to show you this boot process step by step before actually showing
you the boot process practically.
Let me show you it with the help of graphics.
OK.
So let's see here all the steps involved in boot process one by one.
So the first process or the first step in the input process is Pyles milestones for basic input output
system.
So when we power on the button then at this time the system integrity check operation is performed.
OK means it takes for hardware if the hardware is connected to the system properly or not.
OK this is system integrity check.
And if it fails everything is properly connected and working.
Then it searches for MVR and B stands for must have good recall which is present in the first sector
of your hard disk.
OK.
So searches for MVR and loads and execute that and be are OK.
So in short bios performs system integrity check and most Hennig's you can be are OK.
So the next step is via.
So this is located x4 sector or four Hardie's.
OK you can see this at forward.
Let's do.
Or for was let's see.
OK I will show you the part for this.
So the job of this NPR is still load and exit you up.
OK.
So the graphs.
As for Grand Unified bootloader.
OK.
So in short we are sending Zic you the grub.
OK so the next one is grub.
So then we are lost executor up then the job of this group is to launch an exec you the Colonel and
I NIIT are the images.
OK I an idea already stands for initial Ramdas.
OK.
So this group is responsible for loading and executing the kernel and I and I are the images which are
present inside the room directly.
OK I will show you everything when we get in practical mode.
Ok but here first let's understand these steps.
OK.
So Rob Lawson Exit group gerneral and I have an idea are the images.
So at this stage what happens is Colonel and I have an idea ready or executed.
OK.
So an idea of these initial Ramlee it is temporary file system.
Before actually installing the Linux operating system all the system is installed on this temporary
file system in the virtual mode.
OK so what happens is the kernel executes the next step at this step.
OK the next step is initialization system.
So System D is used as initialization system.
In this version of Linux.
OK.
In order to solve a sixteen point ten and seventeen point four if you're going to cover the Woden's
in this course.
OK so what Lloyd-Jones uses in this system the system the service manager which it is used to manage
services in the Linux environment in the older version of Linux.
There are system vi then the upstart.
OK these kinds of services or any larger sense systems are used.
OK so kernel exec use this system.
D.
Ok so the system D is responsible for executing the target key in the system.
The every service or every process is recognized as unique.
OK there are different types of Vionnet insist in the light dot device and Dot target dot.
So with OK these kinds of insider.
So what system did does here ease it.
Exec use the unit called as a runlevel dot target.
OK.
So there are different runlevel dot targets inside there.
There are six levels offered.
So the job of this installation system is to initialize one of these runlevel got targets.
OK.
So by default it executes certainly will file.
OK.
Which is graphical got tagged.
OK so in this way all these steps are in in the boot process.
OK.
So here let me show practic.
So let's get inside our Linux system.
So the first step which is executed by the BIOS is loading and executing and be done.
So let's get inside the and here you can see that's the A is DS present inside this directory.
So the BIOS loads and execute the MVR from this location.
That is silly because it is not present here.
So that's why it uses SD.
OK so after this step the next step is grab.
OK.
Soon grub.
You need to get inside boot key.
OK.
Inside this board you can see here there is a directory grab.
OK.
Listen here you can see there are different files.
So let's hear grab Doxey of this grp configuration file.
OK.
And you can do this file directly if you want to file.
You need to get into another location.
OK.
I wish I knew of a few minutes how to get there but before that let's understand here the importance
of these files.
So this is the globe configuration file.
Let's go out here and identify my new daughter Listy cooking it is a file which is possible for a girl
menu.
OK.
Here you can see that what you saw was sixteen point ten kernel version four cornered zero point twenty
two generic.
OK.
And here after Teigen you can see that hoop has zero is the first sector of hardness as the zero is
fought for a sector of hard disk.
Then the Colonel and I and I d are the images.
So this is the menu for grub.
After this if you want to get the grub.
Then you just need to get inside.
It is the default.
Sorry Alice.
Here you can see there is a fine grub.
So let's get grub again.
This is the file which you can edit if you want to do some changes inside the club.
OK.
So here I'm not with Google that this file right now and after Grug the next step is gerneral and I
and I agree with this.
So in the root directory let's do a list.
I finally and here you can see the files are present here.
That is in the early time the end of the emulator Newsworld but these are not the kill files.
These are siblings.
OK so what is siblings siblings like shot in Windows.
So these are not good for the files which are present in Boot directory.
OK you can see here OK.
So the grub loads and executes these files from these locations OK inside the book.
OK so if the grub kernel and or the images are executed and that we have just seen it here and what
happens is the kernel starts.
System D as its first process.
OK.
So if you want to check that you just need to type this.
I would eat more.
And here you can see at the pub there is a process id one OK for system D.
That means system these the first process executed on this system.
So the kernel starts this system the first process or initial and system you can after this the last
of these runlevel is around level target.
So to check that just get inside library system the system.
OK here.
Different types of files are present.
OK let's do this or
OK in this directory.
You can see here there is a symlink default not target.
OK.
So this default target is similar to graphical dot target.
OK.
So this is the first target executed OK by the system D.
OK.
So and it is actually similar to graphical dark target and you can check here which is the default target
on the system.
OK.
With the help of come on system city get divorced and here you can see it is graphical or Target.
It is the forced process.
OK.
Or you need.
Linux system you can collect as you need it is executed by system D.
OK.
Again get inside this.
OK here you can see there are different levels of targets.
And by default the system is started with graphical or Target.
OK that is it only will fly.
So you can click that it will come on OK it is number five.
So here at the top here you can see there are different levels from zero to six.
So Eastburn level here performs a specific task.
So then you said there are only 1 2 0.
Then our system is going to shut down when we set it run level 1 target then our system cannot start
in a rescue mode in rescue mode.
We can perform different recovery related tasks and for on level 2 3 for all these trivial levels started
in multi user dot target user Our target is a small cookie.
And because of the hardware of this computer not support those functions.
That's why this system is not started in graphical mode.
It is instead small.
OK.
And the runlevel for you is graphical.
Don't get ändern Luas is reboot dot target.
When you set it to six your system won't reboot again and again.
OK.
In this way these six targets are out there.
In this way of Linux.
You can set different was in City Hall or different target ok like this system before and before this.
This system is having graphical target and I want to set it to the user.
Daniel Okay and now I'm sitting in the Maltese are not good now Jake.
Good.
And here you can see now our system is set to move.
These are not target.
OK after this I want to show you some extra things here.
Which system city can you list the dependencies of any kind of unit any unit insert not target or not
device or not service.
OK.
So in this system the system all the processes or services are recognized as units.
OK.
So you can list the dependencies sistem city or system city or
list dependencies.
OK I want to list dependencies for all Natali so you can lose the dependencies for default doc gargled.
OK with the help of this come on.
OK.
Or you can just look at the four dark target.
And here you can see it's his description graphical interface and it has started the Display Manager
so it's ok you can list all the units present in the Linux system with the help of system city.
So just like system city I'll list you next.
All
here you can see different units are there with different extension.
Now here d'arte device then of device it is Mount dot mount dot dot dot.
So this hooking different types of finish inside there.
OK.
So this is how the boot process works in Linux which is based on system the I have all of you understand
all the steps explain no in this lecture.