WEBVTT 00:01.110 --> 00:09.840 Operating systems in the Unix tradition differs from DOS in the MS-DOS traditions, and in that they 00:09.840 --> 00:14.940 are not only multitasking systems but also the multi-user systems. 00:14.940 --> 00:17.490 So what exactly does this means? 00:17.490 --> 00:23.550 If you are asking that, that it means that more than one person can be using a computer at the same 00:23.550 --> 00:24.090 time. 00:24.090 --> 00:32.130 So while a typical computer will likely have only one keyboard and monitor and mouse, it can still 00:32.130 --> 00:34.290 be used by more than one user. 00:34.290 --> 00:44.100 For example, if a computer attached to a network or internet remote users can log in via SSH, secure 00:44.100 --> 00:46.170 shell and operate the computer. 00:46.170 --> 00:52.680 In fact, remote users can execute graphical applications and have graphical output appear on the remote 00:52.830 --> 00:53.550 display. 00:53.550 --> 00:59.250 So the X window system supports this as a part of its basic design. 00:59.280 --> 01:06.130 The multi-user capability of Linux is not a recent innovative innovation, but rather a feature that 01:06.130 --> 01:09.610 is deeply embedded into the design of the operating system. 01:09.610 --> 01:15.310 Considering the environment in which the Unix was created, this makes perfect sense. 01:15.310 --> 01:21.040 Years ago, before computers were personal, they were larger, expensive and centralized. 01:21.040 --> 01:28.990 So a typical university computer system, for example, consists of a large central computer located 01:29.380 --> 01:34.270 in one building and terminals that were located throughout on the campus, for example. 01:34.270 --> 01:43.270 This is our computer and this is our terminals that is located throughout our university campus. 01:44.350 --> 01:52.540 So each and each of these nodes connected to the large central computer, which in this case it's our 01:52.540 --> 01:54.190 large central computer, is this. 01:54.390 --> 01:55.300 So. 01:56.760 --> 01:58.320 Now to make this practical. 01:59.450 --> 02:04.440 A method had to be devised to protect the users from each other. 02:04.480 --> 02:04.970 Right. 02:04.970 --> 02:10.910 So after all, the actions of one user could not be affected. 02:11.030 --> 02:16.040 Actions of one user cannot be affected by. 02:16.880 --> 02:17.190 Um. 02:18.720 --> 02:19.620 Many users. 02:19.620 --> 02:24.780 So here, let's actually draw our person right here. 02:24.780 --> 02:34.050 So the action of our one user could not be allowed to crash the computer nor couldn't kill could one 02:34.050 --> 02:36.060 user interface with the files. 02:36.060 --> 02:42.210 For example, this is belonging with our this username is Max and this is Carl. 02:42.390 --> 02:51.120 So the Carl could not access our Max files or Max cannot access Carl's files. 02:51.120 --> 02:52.170 So that's it. 02:52.170 --> 02:57.780 That's a that's it with our user permissions which you will learn in this section. 02:57.780 --> 03:00.660 So to make this practical. 03:02.210 --> 03:05.540 You will learn the ID command. 03:05.660 --> 03:07.970 Actually, let me delete all of this. 03:07.970 --> 03:14.880 And so in this lecture you will learn about the I'd command in terminal. 03:14.900 --> 03:19.330 So this ID command we are going to use to display the user identity identity. 03:19.610 --> 03:24.960 You will learn also learn about the C harsh mode command. 03:24.980 --> 03:29.090 So this command will change a file's mode. 03:29.120 --> 03:30.350 You will also learn. 03:30.350 --> 03:31.490 You mask. 03:31.520 --> 03:32.930 You mask. 03:35.170 --> 03:40.030 And this u-mask we're going to use this u-mask command to set the default file permission. 03:40.030 --> 03:52.060 You will learn about the sudo sudo the sudo is to execute a command as another user, but su means run 03:52.060 --> 03:54.400 a shell as another user. 03:54.400 --> 04:00.190 So you will learn about these differences between su and sudo in this section. 04:00.190 --> 04:03.160 And then also you will learn about three. 04:03.920 --> 04:16.310 Thermal commands, which is c hard o w n which this will change the file's owner and c h. 04:17.160 --> 04:20.100 G r p. 04:20.460 --> 04:25.050 Also, this will change a file's group ownership. 04:25.380 --> 04:28.470 And we also have P. 04:28.500 --> 04:31.050 Actually, let me write this right down here. 04:31.230 --> 04:33.120 So we will also learn. 04:33.150 --> 04:38.970 P a s s w d which. 04:39.630 --> 04:43.850 With this command, you can change a user's password. 04:43.890 --> 04:50.700 In next lecture, you will learn about the Jonas Group members and everybody else in Cali in General 04:50.700 --> 04:51.510 Linux systems. 04:51.510 --> 04:53.520 So I'm waiting you in next lecture.