Operating systems in the Unix tradition differs from DOS in the MS-DOS traditions, and in that they
are not only multitasking systems but also the multi-user systems.
So what exactly does this means?
If you are asking that, that it means that more than one person can be using a computer at the same
time.
So while a typical computer will likely have only one keyboard and monitor and mouse, it can still
be used by more than one user.
For example, if a computer attached to a network or internet remote users can log in via SSH, secure
shell and operate the computer.
In fact, remote users can execute graphical applications and have graphical output appear on the remote
display.
So the X window system supports this as a part of its basic design.
The multi-user capability of Linux is not a recent innovative innovation, but rather a feature that
is deeply embedded into the design of the operating system.
Considering the environment in which the Unix was created, this makes perfect sense.
Years ago, before computers were personal, they were larger, expensive and centralized.
So a typical university computer system, for example, consists of a large central computer located
in one building and terminals that were located throughout on the campus, for example.
This is our computer and this is our terminals that is located throughout our university campus.
So each and each of these nodes connected to the large central computer, which in this case it's our
large central computer, is this.
So.
Now to make this practical.
A method had to be devised to protect the users from each other.
Right.
So after all, the actions of one user could not be affected.
Actions of one user cannot be affected by.
Um.
Many users.
So here, let's actually draw our person right here.
So the action of our one user could not be allowed to crash the computer nor couldn't kill could one
user interface with the files.
For example, this is belonging with our this username is Max and this is Carl.
So the Carl could not access our Max files or Max cannot access Carl's files.
So that's it.
That's a that's it with our user permissions which you will learn in this section.
So to make this practical.
You will learn the ID command.
Actually, let me delete all of this.
And so in this lecture you will learn about the I'd command in terminal.
So this ID command we are going to use to display the user identity identity.
You will learn also learn about the C harsh mode command.
So this command will change a file's mode.
You will also learn.
You mask.
And this u-mask we're going to use this u-mask command to set the default file permission.
You will learn about the sudo sudo the sudo is to execute a command as another user, but su means run
a shell as another user.
So you will learn about these differences between su and sudo in this section.
And then also you will learn about three.
Thermal commands, which is c hard o w n which this will change the file's owner and c h.
G r p.
Also, this will change a file's group ownership.
And we also have P.
Actually, let me write this right down here.
So we will also learn.
P a s s w d which.
With this command, you can change a user's password.
In next lecture, you will learn about the Jonas Group members and everybody else in Cali in General
Linux systems.
So I'm waiting you in next lecture.