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Operating systems in the Unix tradition differs from DOS in the MS-DOS traditions, and in that they

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are not only multitasking systems but also the multi-user systems.

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So what exactly does this means?

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If you are asking that, that it means that more than one person can be using a computer at the same

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time.

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So while a typical computer will likely have only one keyboard and monitor and mouse, it can still

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be used by more than one user.

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For example, if a computer attached to a network or internet remote users can log in via SSH, secure

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shell and operate the computer.

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In fact, remote users can execute graphical applications and have graphical output appear on the remote

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display.

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So the X window system supports this as a part of its basic design.

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The multi-user capability of Linux is not a recent innovative innovation, but rather a feature that

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is deeply embedded into the design of the operating system.

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Considering the environment in which the Unix was created, this makes perfect sense.

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Years ago, before computers were personal, they were larger, expensive and centralized.

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So a typical university computer system, for example, consists of a large central computer located

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in one building and terminals that were located throughout on the campus, for example.

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This is our computer and this is our terminals that is located throughout our university campus.

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So each and each of these nodes connected to the large central computer, which in this case it's our

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large central computer, is this.

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So.

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Now to make this practical.

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A method had to be devised to protect the users from each other.

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Right.

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So after all, the actions of one user could not be affected.

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Actions of one user cannot be affected by.

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Um.

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Many users.

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So here, let's actually draw our person right here.

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So the action of our one user could not be allowed to crash the computer nor couldn't kill could one

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user interface with the files.

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For example, this is belonging with our this username is Max and this is Carl.

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So the Carl could not access our Max files or Max cannot access Carl's files.

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So that's it.

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That's a that's it with our user permissions which you will learn in this section.

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So to make this practical.

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You will learn the ID command.

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Actually, let me delete all of this.

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And so in this lecture you will learn about the I'd command in terminal.

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So this ID command we are going to use to display the user identity identity.

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You will learn also learn about the C harsh mode command.

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So this command will change a file's mode.

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You will also learn.

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You mask.

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You mask.

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And this u-mask we're going to use this u-mask command to set the default file permission.

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You will learn about the sudo sudo the sudo is to execute a command as another user, but su means run

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a shell as another user.

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So you will learn about these differences between su and sudo in this section.

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And then also you will learn about three.

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Thermal commands, which is c hard o w n which this will change the file's owner and c h.

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G r p.

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Also, this will change a file's group ownership.

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And we also have P.

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Actually, let me write this right down here.

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So we will also learn.

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P a s s w d which.

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With this command, you can change a user's password.

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In next lecture, you will learn about the Jonas Group members and everybody else in Cali in General

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Linux systems.

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So I'm waiting you in next lecture.