Starting with Linux, need help on users!

[filete]

Hi there.

Im starting to use Linux, doing some tests on a dedicated server
I own, so I have all the root permissions.
I´m still learning the commands and go thru all the system,
so I would like to have some help on these issues that I can´t
just figure out myself:

1 - When I create a new user, lets say useradd user1, why does
it not ask for any password? Even if I create several users this
way, I can go from one user to another with no password asking.
And go back to my root account again, and still dont ask me any
password.

2 - How the processes in Linux work for each user?
Are they complete independent from each user? So it does not
mess with each other processes?

3 - relate to 2 question too:
Can I install different programs for each user, so each
work with the app they need on the Linux machine?

I think its about it for now!
Thanks

[vsemaska]

I'll answer question 1. When you use useradd you would have to pass the encrypted password as part of the -p option. I won't go into how to encrypt a password. The best thing to do is after you create the account, say user1, then use:

passwd user1

[filete]

I'll answer question 1. When you use useradd you would have to pass the encrypted password as part of the -p option. I won't go into how to encrypt a password. The best thing to do is after you create the account, say user1, then use:

passwd user1

Thank you,
How about the 2 question, can someone light me
how does Linux deal with the processes of each user?

[filete]

Can I have some help on this?
Thanks!

[jayd512]

Hello and Welcome!
I'll give it a shot.

2 - How the processes in Linux work for each user?
Are they complete independent from each user? So it does not
mess with each other processes?

Most processes are pretty much independent of each other on a user to user basis. Meaning that all files and data for, let's say user1, will not affect anything related to user2. You would actually have to make a few small changes to the files/data permissions to allow another user to even be able to read the files. for that, take a look at

man chmod

3 - relate to 2 question too:
Can I install different programs for each user, so each
work with the app they need on the Linux machine?

Yep, sure can! Linux is meant to be a true multi-user OS. So each user profile that is set up will be able to access whatever app they need. On the other hand, you can also arrange permissions to deny access to certain apps. For example, if I'm set-up to just work on spreadsheets and such, why would I need to access games or internet?

[darkrose0510]

2 - How the processes in Linux work for each user?
Are they complete independent from each user? So it does not
mess with each other processes?

The short answer is yes. The Long answer is that it all comes down to permissions, no user can run a process that can affect another users process/es. Unless they are root or have root priveleges, in which case they can do anything they want. But no process can affect another users process, even if called by root, unless it is specifically told to (such as using kill to end a process) and has permission to (root can do anything, users can't touch other users, and users can't touch root).

3 - relate to 2 question too:
Can I install different programs for each user, so each
work with the app they need on the Linux machine?

Yes you can, I've never done it but I can think of several ways to do this:
actually install applications in a users home directory so that only they can run the application.
As above, but install in /usr/local/<username>
With permissions, make applications executable only by certain groups, and then users only to the groups you want.
If you're running a gui could edit their menu so that they only have certain apps; this is the easiest but least effective.

[filete]

Thanks to all!
I got it now