WEBVTT 00:01.530 --> 00:07.130 Friends welcome back in this lesson we can learn about Linux boot process in detail. 00:07.480 --> 00:09.250 So what is that process. 00:09.430 --> 00:15.280 When we powered on our computer then after a few minutes we get the log in prompt. 00:15.370 --> 00:15.790 OK. 00:15.820 --> 00:23.050 So the process in Word in between when the power on the button do until we get the logon prompt is called 00:23.050 --> 00:25.140 as the boot process. 00:25.150 --> 00:31.630 So here in this lesson I would like to show you this boot process step by step before actually showing 00:31.630 --> 00:33.730 you the boot process practically. 00:33.730 --> 00:36.960 Let me show you it with the help of graphics. 00:36.970 --> 00:37.490 OK. 00:37.690 --> 00:42.600 So let's see here all the steps involved in boot process one by one. 00:42.880 --> 00:51.400 So the first process or the first step in the input process is Pyles milestones for basic input output 00:51.400 --> 00:52.130 system. 00:52.300 --> 00:59.810 So when we power on the button then at this time the system integrity check operation is performed. 01:00.030 --> 01:06.050 OK means it takes for hardware if the hardware is connected to the system properly or not. 01:06.050 --> 01:08.440 OK this is system integrity check. 01:08.560 --> 01:13.120 And if it fails everything is properly connected and working. 01:13.120 --> 01:21.940 Then it searches for MVR and B stands for must have good recall which is present in the first sector 01:21.940 --> 01:23.250 of your hard disk. 01:23.440 --> 01:23.930 OK. 01:24.130 --> 01:29.140 So searches for MVR and loads and execute that and be are OK. 01:29.350 --> 01:35.900 So in short bios performs system integrity check and most Hennig's you can be are OK. 01:36.130 --> 01:38.470 So the next step is via. 01:38.680 --> 01:43.640 So this is located x4 sector or four Hardie's. 01:43.690 --> 01:46.820 OK you can see this at forward. 01:46.850 --> 01:48.010 Let's do. 01:48.050 --> 01:50.340 Or for was let's see. 01:50.530 --> 01:53.890 OK I will show you the part for this. 01:53.890 --> 01:58.760 So the job of this NPR is still load and exit you up. 01:59.020 --> 01:59.620 OK. 01:59.920 --> 02:00.710 So the graphs. 02:00.730 --> 02:03.220 As for Grand Unified bootloader. 02:03.480 --> 02:04.030 OK. 02:04.120 --> 02:07.440 So in short we are sending Zic you the grub. 02:07.720 --> 02:11.120 OK so the next one is grub. 02:11.500 --> 02:19.510 So then we are lost executor up then the job of this group is to launch an exec you the Colonel and 02:19.600 --> 02:21.300 I NIIT are the images. 02:21.350 --> 02:24.520 OK I an idea already stands for initial Ramdas. 02:24.720 --> 02:25.230 OK. 02:25.390 --> 02:34.300 So this group is responsible for loading and executing the kernel and I and I are the images which are 02:34.300 --> 02:36.330 present inside the room directly. 02:36.490 --> 02:40.540 OK I will show you everything when we get in practical mode. 02:40.690 --> 02:45.400 Ok but here first let's understand these steps. 02:45.630 --> 02:45.980 OK. 02:45.990 --> 02:50.570 So Rob Lawson Exit group gerneral and I have an idea are the images. 02:50.890 --> 02:55.790 So at this stage what happens is Colonel and I have an idea ready or executed. 02:56.140 --> 02:56.630 OK. 02:56.770 --> 03:01.250 So an idea of these initial Ramlee it is temporary file system. 03:01.450 --> 03:08.380 Before actually installing the Linux operating system all the system is installed on this temporary 03:08.380 --> 03:10.940 file system in the virtual mode. 03:11.080 --> 03:17.890 OK so what happens is the kernel executes the next step at this step. 03:18.040 --> 03:20.530 OK the next step is initialization system. 03:20.650 --> 03:23.960 So System D is used as initialization system. 03:23.980 --> 03:25.540 In this version of Linux. 03:25.570 --> 03:26.210 OK. 03:26.230 --> 03:32.500 In order to solve a sixteen point ten and seventeen point four if you're going to cover the Woden's 03:32.560 --> 03:33.770 in this course. 03:33.970 --> 03:41.440 OK so what Lloyd-Jones uses in this system the system the service manager which it is used to manage 03:41.440 --> 03:46.440 services in the Linux environment in the older version of Linux. 03:46.510 --> 03:49.850 There are system vi then the upstart. 03:49.940 --> 03:54.440 OK these kinds of services or any larger sense systems are used. 03:54.700 --> 03:57.940 OK so kernel exec use this system. 03:57.950 --> 03:58.620 D. 03:58.750 --> 04:06.860 Ok so the system D is responsible for executing the target key in the system. 04:06.860 --> 04:11.850 The every service or every process is recognized as unique. 04:11.950 --> 04:19.550 OK there are different types of Vionnet insist in the light dot device and Dot target dot. 04:19.550 --> 04:23.260 So with OK these kinds of insider. 04:23.380 --> 04:25.920 So what system did does here ease it. 04:25.950 --> 04:30.330 Exec use the unit called as a runlevel dot target. 04:30.430 --> 04:31.270 OK. 04:31.270 --> 04:35.640 So there are different runlevel dot targets inside there. 04:35.970 --> 04:37.670 There are six levels offered. 04:37.690 --> 04:44.410 So the job of this installation system is to initialize one of these runlevel got targets. 04:44.620 --> 04:45.340 OK. 04:45.550 --> 04:49.310 So by default it executes certainly will file. 04:49.450 --> 04:49.950 OK. 04:50.080 --> 04:51.910 Which is graphical got tagged. 04:52.050 --> 04:58.110 OK so in this way all these steps are in in the boot process. 04:58.390 --> 04:58.980 OK. 04:59.110 --> 05:01.300 So here let me show practic. 05:01.590 --> 05:05.100 So let's get inside our Linux system. 05:05.100 --> 05:11.090 So the first step which is executed by the BIOS is loading and executing and be done. 05:11.250 --> 05:21.590 So let's get inside the and here you can see that's the A is DS present inside this directory. 05:21.860 --> 05:27.130 So the BIOS loads and execute the MVR from this location. 05:27.140 --> 05:32.000 That is silly because it is not present here. 05:32.150 --> 05:34.510 So that's why it uses SD. 05:34.700 --> 05:38.890 OK so after this step the next step is grab. 05:39.040 --> 05:39.590 OK. 05:39.710 --> 05:40.580 Soon grub. 05:40.590 --> 05:43.960 You need to get inside boot key. 05:47.920 --> 05:48.530 OK. 05:48.800 --> 05:52.510 Inside this board you can see here there is a directory grab. 05:52.820 --> 05:53.910 OK. 05:54.170 --> 05:57.230 Listen here you can see there are different files. 05:57.250 --> 06:03.080 So let's hear grab Doxey of this grp configuration file. 06:03.240 --> 06:03.850 OK. 06:03.860 --> 06:08.220 And you can do this file directly if you want to file. 06:08.360 --> 06:11.270 You need to get into another location. 06:11.480 --> 06:11.910 OK. 06:12.110 --> 06:18.800 I wish I knew of a few minutes how to get there but before that let's understand here the importance 06:18.800 --> 06:19.560 of these files. 06:19.580 --> 06:22.310 So this is the globe configuration file. 06:22.670 --> 06:31.330 Let's go out here and identify my new daughter Listy cooking it is a file which is possible for a girl 06:31.400 --> 06:32.000 menu. 06:32.170 --> 06:32.450 OK. 06:32.490 --> 06:38.790 Here you can see that what you saw was sixteen point ten kernel version four cornered zero point twenty 06:38.840 --> 06:40.020 two generic. 06:40.220 --> 06:40.770 OK. 06:40.770 --> 06:48.060 And here after Teigen you can see that hoop has zero is the first sector of hardness as the zero is 06:48.060 --> 06:50.720 fought for a sector of hard disk. 06:50.790 --> 06:54.630 Then the Colonel and I and I d are the images. 06:54.630 --> 06:57.880 So this is the menu for grub. 06:58.560 --> 07:02.180 After this if you want to get the grub. 07:02.370 --> 07:04.590 Then you just need to get inside. 07:04.660 --> 07:09.030 It is the default. 07:09.180 --> 07:11.940 Sorry Alice. 07:12.030 --> 07:14.710 Here you can see there is a fine grub. 07:14.760 --> 07:18.460 So let's get grub again. 07:18.570 --> 07:23.910 This is the file which you can edit if you want to do some changes inside the club. 07:24.080 --> 07:24.700 OK. 07:25.020 --> 07:31.860 So here I'm not with Google that this file right now and after Grug the next step is gerneral and I 07:31.860 --> 07:33.390 and I agree with this. 07:33.420 --> 07:36.560 So in the root directory let's do a list. 07:36.580 --> 07:40.770 I finally and here you can see the files are present here. 07:40.770 --> 07:47.570 That is in the early time the end of the emulator Newsworld but these are not the kill files. 07:47.580 --> 07:48.950 These are siblings. 07:49.050 --> 07:54.130 OK so what is siblings siblings like shot in Windows. 07:54.450 --> 07:58.540 So these are not good for the files which are present in Boot directory. 07:58.710 --> 08:01.570 OK you can see here OK. 08:01.640 --> 08:07.920 So the grub loads and executes these files from these locations OK inside the book. 08:08.070 --> 08:18.320 OK so if the grub kernel and or the images are executed and that we have just seen it here and what 08:18.320 --> 08:20.180 happens is the kernel starts. 08:20.180 --> 08:23.620 System D as its first process. 08:23.820 --> 08:24.310 OK. 08:24.500 --> 08:29.250 So if you want to check that you just need to type this. 08:29.300 --> 08:33.620 I would eat more. 08:33.890 --> 08:40.120 And here you can see at the pub there is a process id one OK for system D. 08:40.160 --> 08:46.220 That means system these the first process executed on this system. 08:46.670 --> 08:55.390 So the kernel starts this system the first process or initial and system you can after this the last 08:55.390 --> 08:59.190 of these runlevel is around level target. 08:59.510 --> 09:07.130 So to check that just get inside library system the system. 09:07.640 --> 09:09.450 OK here. 09:09.680 --> 09:12.010 Different types of files are present. 09:12.230 --> 09:16.710 OK let's do this or 09:27.990 --> 09:29.640 OK in this directory. 09:29.830 --> 09:34.500 You can see here there is a symlink default not target. 09:34.630 --> 09:35.300 OK. 09:35.530 --> 09:40.400 So this default target is similar to graphical dot target. 09:40.570 --> 09:41.140 OK. 09:41.140 --> 09:46.400 So this is the first target executed OK by the system D. 09:46.690 --> 09:47.360 OK. 09:47.410 --> 09:56.170 So and it is actually similar to graphical dark target and you can check here which is the default target 09:56.290 --> 09:57.610 on the system. 09:57.670 --> 09:58.120 OK. 09:58.240 --> 10:08.200 With the help of come on system city get divorced and here you can see it is graphical or Target. 10:08.260 --> 10:09.930 It is the forced process. 10:09.940 --> 10:10.300 OK. 10:10.300 --> 10:11.230 Or you need. 10:12.070 --> 10:16.550 Linux system you can collect as you need it is executed by system D. 10:16.840 --> 10:17.510 OK. 10:17.860 --> 10:19.700 Again get inside this. 10:19.930 --> 10:24.140 OK here you can see there are different levels of targets. 10:24.400 --> 10:28.780 And by default the system is started with graphical or Target. 10:28.810 --> 10:30.820 OK that is it only will fly. 10:31.240 --> 10:38.910 So you can click that it will come on OK it is number five. 10:39.130 --> 10:44.350 So here at the top here you can see there are different levels from zero to six. 10:44.380 --> 10:47.610 So Eastburn level here performs a specific task. 10:47.620 --> 10:49.910 So then you said there are only 1 2 0. 10:49.920 --> 10:57.940 Then our system is going to shut down when we set it run level 1 target then our system cannot start 10:57.940 --> 11:00.070 in a rescue mode in rescue mode. 11:00.070 --> 11:09.880 We can perform different recovery related tasks and for on level 2 3 for all these trivial levels started 11:09.910 --> 11:16.890 in multi user dot target user Our target is a small cookie. 11:17.200 --> 11:22.510 And because of the hardware of this computer not support those functions. 11:22.510 --> 11:26.100 That's why this system is not started in graphical mode. 11:26.200 --> 11:27.590 It is instead small. 11:27.720 --> 11:28.300 OK. 11:28.600 --> 11:31.340 And the runlevel for you is graphical. 11:31.380 --> 11:35.100 Don't get ändern Luas is reboot dot target. 11:35.110 --> 11:40.830 When you set it to six your system won't reboot again and again. 11:41.110 --> 11:41.540 OK. 11:41.620 --> 11:46.020 In this way these six targets are out there. 11:46.460 --> 11:49.210 In this way of Linux. 11:49.390 --> 12:02.240 You can set different was in City Hall or different target ok like this system before and before this. 12:02.540 --> 12:11.320 This system is having graphical target and I want to set it to the user. 12:11.430 --> 12:22.140 Daniel Okay and now I'm sitting in the Maltese are not good now Jake. 12:22.350 --> 12:24.160 Good. 12:24.630 --> 12:28.320 And here you can see now our system is set to move. 12:28.320 --> 12:29.850 These are not target. 12:30.240 --> 12:33.360 OK after this I want to show you some extra things here. 12:33.550 --> 12:42.270 Which system city can you list the dependencies of any kind of unit any unit insert not target or not 12:42.270 --> 12:44.470 device or not service. 12:44.490 --> 12:44.960 OK. 12:45.180 --> 12:52.190 So in this system the system all the processes or services are recognized as units. 12:52.340 --> 12:52.850 OK. 12:53.130 --> 12:59.700 So you can list the dependencies sistem city or system city or 13:03.160 --> 13:04.670 list dependencies. 13:04.980 --> 13:14.020 OK I want to list dependencies for all Natali so you can lose the dependencies for default doc gargled. 13:14.110 --> 13:16.120 OK with the help of this come on. 13:16.540 --> 13:17.480 OK. 13:17.550 --> 13:23.610 Or you can just look at the four dark target. 13:23.970 --> 13:30.470 And here you can see it's his description graphical interface and it has started the Display Manager 13:30.480 --> 13:37.990 so it's ok you can list all the units present in the Linux system with the help of system city. 13:38.410 --> 13:45.230 So just like system city I'll list you next. 13:45.420 --> 13:45.720 All 13:48.740 --> 13:53.240 here you can see different units are there with different extension. 13:53.270 --> 14:01.610 Now here d'arte device then of device it is Mount dot mount dot dot dot. 14:01.610 --> 14:05.460 So this hooking different types of finish inside there. 14:06.050 --> 14:06.400 OK. 14:06.410 --> 14:14.570 So this is how the boot process works in Linux which is based on system the I have all of you understand 14:14.600 --> 14:17.810 all the steps explain no in this lecture.