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I am using ubuntu 12.04 LTS edition 32 bit and Now these days I am working on Ubuntu Customization. My customization OS having 2 users as follows:

  1. Administrator with full permission.
  2. Net user(Standard User) with limited permission.

Now I am installing some external packages and commands and now i want that my Net user couldn't access them.

Any Idea?

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In the POSIX systems, there are 3 modes of accessing a file: owner User, Group and Others with 3 types of permissions: Read/Write/eXecute. There is a bitmask for each file on system which contains those permissions. Read more…

The basic idea is to put Net User to others and deny others Read/Write/Execute the particular file. This is done by

sudo chmod 750 /path/to/file_or_directory

Initially, the others is the group where each new user appears. So if you want to deny them from accessing Bash, you have to write

sudo chmod 750 /bin/bash

This will set permissions to rwxr-x---. To allow access again, use

sudo chmod 755 /bin/bash
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In Ubuntu Linux operating systems, the root account is blocked and cannot be used by users who do not have 'superuser' rights. To enable the root privileges on a user's account, sudo or gksu commands can be used. The sudo command in Linux allows users to set up the password mode for the root users in order to activate the console sessions in command mode only. The graphical user interface cannot be accessed with the sudo commands. To enable the root privileges on a graphical user interface, the login and security settings have to be changed through the administration tools.

Here the Solution to access the Administrator is:

To enable the root account and access directly via the console in root mode, you must type the command:

sudo passwd root    

This command allows you to set up the password mode for the root user which will be activated for the console sessions only (no GUI). Once the password is initialized, it will be possible to open a console session with the user root.

Note that:-

To enable access to the graphical user root, go to System/Administration/Login, click the Security tab, then tick the box allowing connection of the local System Administrator. Disconnect and reconnect with the root account.

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Are you sure you answering the OP's question? – Danatela Mar 25 '14 at 9:27

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