Skip to main content

Users and Groups in Linux - 1

Users :
Linux is Multi user environment. The users are those who can access the operating system resources with proper permissions as defined already.

Types of users :
I.   System Users
II.  Root User
III. Normal Users

I. System Users - They are default user in linux for some system process and service.
II. Root User - Root user is administrator of Linux System. He have all rights in machine. So should be very carefully with root user. Unknown mistakes may crash the system.
III. Normal Users - They are created by us for some reasons. They are limited users.

Groups : 
Groups are Logical experiences for tying users together. Normally groups are used to share files and permissions.

Types of groups :
I.   System Groups
II.  Root Group
III. Normal Groups

I.   System Groups - They are default groups in linux for some system process and services.
II.  Root Group - Root group is administrator group of Linux System.
III. Normal Groups - They are created by us for some reasons. They are limited groups.

Create User :
Normally we won't and can't create System users, It'll be created by system and or applications for services and maintainable. Root user will be created at the time of Linux installation.
for create a normal user we'll use the command "adduser".
We can use adduser command with root user only.

"useradd" command used to create a user. 
"passwd" command used to create password for user.

[root@server ~]# useradd user1
[root@server ~]# passwd user1

* Typed password won't be shown at terminal window
** Won't ask for password conformation for second time with root. (re enter password)

Create Group :
It also same as user. But When we create a user, the group for the user will be created with same name. A user must be with in a group. Two basic classifications in groups.

i   Primary Group
ii  Secondary Group

Primary Group - The user should be created with this group. He have all rights with in this group.
Secondary Group - The user may or may not have secondary group. And he may or may not have full rights with in this group.

"groupadd" command used to create a group.
[root@server ~]# groupadd group1

User ID & Group ID
UID stored in /etc/passwd
GID stored in /etc/group

UID and GID are unique number for users and groups.
User and Group ID start with 0 and end with 65535.
0 - root user and group
1 - 500 for system users and groups
501 - 60000 for Normal user and groups
60001 - 65535 for duplicate user and group id.
A user can be assigned with multiple ID and these multiple ID numbers are chosen from this range of Duplicate ID range.

* Use man pages for more help.

While searching about it i got following questions :
i      How to create user without group ?
ii     How to create user with already created group ?
iii    How to create user without password ?
iv    How to create user with more groups ?
v     Is possible to change primary group of user ?
vi    How to remove user from the group ?
vii   How to delete a user ?
viii  How to delete a group ?  
ix    How to make a user as root privileged ?
x     Is it possible to edit passwd / group file manually ? And it take affects in user and group ?
xii   Is it possible to create a user without user directory and how ?


Popular posts from this blog

Install and Uninstall VMware .bundle in Redhat - RHEL 6

Here the steps for Install and Uninstall VMware .bundle in Redhat and also Linux. I have checked with RHEL 6.

For install :
Login in as root user, Type following command

~]# sh VMware-***.bundle

Here *** will be your software and it's version.

This command will display normal GUI installation. Choose option as your wish.

For Uninstall :
Login in as root user, Type following command

~]# vmware-installer -l

This will display your product name and product version installed by VMware.

Product Name         Product Version    
========== ==============

Note Name and Version, Use following command to uninstall

~]# vmware-installer -u {product-name} {product-version}

~]# vmware-installer -u vmware-workstation

Now you can uninstall with GUI.

* This is common for all VMware .bundle installation files. Ex: VMware-Workstation, VMware-Player etc.

Play NFS (Need For Speed) or other Games on Full Screen in Laptop with Windows 7

Now a days most of people playing NFS serious (NFS Most Wanted , NFS Carbon etc.) in Laptop.

We are facing the problem that NFS game does not play in full screen mode. It have some black bar at both right and left side.

We can fix it with simple steps, For this your video driver should be installed with it's "Graphics & Media Control Panel" application.

Here i have explained it with screen shot. It'll be mostly same for Intel boards. Settings for other video drivers may differ. You may need to search for it in their graphics control panel.

Step 1 :

Click aero button at right bottom corner for show available notifications and running process. There is Graphics & Media Control Panel Icon.
If it is not avaliable there, you can get it from "Windows Control Panel". It'll open your "Graphics & Media Control Panel".

Step 2 :

Click Graphics & Media Control Panel icon and choose Graphics Properties...

Step 3:

Under Intel Graphics and …