Modifying User Accounts

Modifying User Accounts :
Modifies a user account.

1) Launch Userconf
2) Choose User Accounts & Click User Accounts
3) Modify & Press Enter
4) Modify the Fields
5) Click Accept Button


Name :
usermod –> modify a user account

Usermod Command :
The usermod command lets you modify an existing user account.

Syn :

usermod [options] LOGIN

Description :
The usermod command modifies the system account files to reflect the changes that are specified on the command line.

Cmd :

usermod -d home
usermod -l home

Chfn Command :
The chfn command change the full name associated with a user account.

Cmd :

chfn user

Chsh Commands :
The chsh command change the command interpreter associated with user account.

Cmd :

chsh -s shell user

usermod options

Usermod Files :
/etc/group       –> Group account information.
/etc/gshadow   –> Secure group account information.
/etc/login.defs –> Shadow password suite configuration.
/etc/passwd     –> User account information.
/etc/shadow     –> Secure user account information.

Disk Space Quota

Quota :
A disk quota is a limit set by a system administrator that restricts certain aspects of file system usage on modern operating systems. The function of using disk quotas is to allocate limited disk space in a reasonable way.Disk Space Quota place limits on the amount of the disk space a User (or) Group.

1) quota.user


Types of Limits :
1) Soft Limits
2) Hard Limits

Implementing Quotas :
1) Configure the kernal
2) Install quota package
3) /etc/fstab
4) Establishes quota files
5) Set quotas
6) Turn on quota checking

Installing Quota Package :
The quota package is part of the redhat linux base component and generally installed.

Cmd :

rpm -qi quota

Cmd :

rpm -uvh quota*.rpm

Resides :

1) Runs quota check on root file system
2) Runs quota check on other file system
3) Runs on quota checking

Revising /etc/fstab :
To specify that a partition supports disk quotas.

/dev/hda8  /      ext2  default 1  1
/dev/hda5  /boot  ext2  default 1  2
/dev/hda6  /home  ext2  default 1  2
/dev/hda7  /usr   ext2  default 1  2

User disk quotas :
/dev/hda6  /home  ext2  default usrquota 1  2

Group disk quotas :
/dev/hda6  /home  ext2  default grpquota 1  2

User & Group quotas :
/dev/hda6  /home  ext2  default usrquota, grpquota 1  2

remount :
mount -o remount /home

Quota check files :
quotacheck -arug

Kickstart Basic Information

What is Kickstart
Installing Red Hat based systems from physical or virtual media is easy enough when there is only one or two hosts to install. Beyond this, when an administrator needs to setup several Linux systems, Kickstart can provide a relatively easy way to accomplish mass deployment and can be totally automated.


Kickstart Installation
A Kickstart Installation is a special type of installation in which responce to installation dialog boxes are taken from script.


Using Kickstart
MKKickstart program is not installed by default.

rpm -uvh /mnt/cdrom/redhat/rpms/kickstart*.rpm

Run MKkickstart
mkkickstart > ks.cfg

Editing Configuration File
The system to obtain its network configuration via BOOTP (or) DHCP.

network –bootproto BOOTP
network –bootproto DHCP

Linux Installation Via Live CD

Make a Bootable Drive
Alternatively you can burn a DVD drive using Brasero CD/DVD burning software.

Begin Installation
click on the Install to Hard Drive icon on the desktop.

Desktop Install to Hard Drive

Select Language And KeyboardSelect Language

 Change The Installation DestinationAutomatic Partitioning

 Installation DestinationConfigure Partitioning

Select The Partitioning SchemeSelect Partitioning Scheme

Create a Swap SpaceCreate Swap Space

Create a Mount PointCreate a Mount Point

Accept ChangesAccept Changes

Set Date & TimeSet Date and Time

Begin InstallationBegin Installation

Configurationconfiguration during installation

Set Up Root PasswordSet Up Root Password

Create a User AccountCreate a User Account

Complete InstallationInstalling Bootloader

Installation is Completed

Complete Installation

CentOS 7 Installation

CentOS 7
The second CentOS-7 release. The CentOS Linux distribution is a stable, predictable, manageable and reproducible platform derived from the sources of Red Hat Enterprise Linux (RHEL)1.CentOS conforms fully with Red Hats redistribution policy and aims to have full functional compatibility with the upstream product. CentOS mainly changes packages to remove Red Hats branding and artwork.

CentOS 7 uses XFS as its default file system.
OpenJDK-7 is the default JDK.
initd has been replaced by systemd.
New Linux Kernel 3.10.0, support for Linux Containers, and the inclusion of the Open VMware Tools and 3D graphics drivers out of the box.

System Requirements
512MB RAM – 32Bit OS
1024MB RAM – 64BIT OS
1GB+More – RAM
Supports i386 Systems (32-bit Pentium, AMD)
Supports x86_64 systems (AMD64/EM64T)
Maximum logical CPUs10 – 32
Maximum memory – 16GB
Disk Space – 8GB
Free Memory – 1GB

64 Bit ISO

64 Bit Torrent

CentOS 7 Installation
Installation of CentOS 7


Choose your language


Change the Installation Destination


Change partition & Click done


Create a partition table


Click on accept changes


Select Time Zone


Configure Networking and Set the hostname


Click on software selection


Click on begin installation


Set root password


Create a user


Installation is in progress


Installation is completed


Accept the EULA agreement


CentOS 7 Screen


File System Structure


File System Structure
It contains binaries are basic command line utilities. These commands only can execute by both root as well as the normal user.

It contains boot loader files, image of the kernel and init.rd information.
Boot Loader contains bootable files and commands which are required to boot the Operating System. There are two different types of Linux boot loaders are there.
LILO (Linux Loader)
GRUB (Grand Unified Bootable Loader) 

It contains Hardware Devices information.

It contains Operating System main configuration files.

It contains normal users home directories information.

It Contains library files that supports the binaries located under /bin and /sbin

It Displays mount point for Removable Devices.

It contains temporary mount points for the Hardware Devices.

It contains third party applications information.

It contains Super Users binary information.

Contains server specific services related data.

It contains temporary files and downloaded files information.

Majority of the Operating System will be loaded into the Sub Directory and it Contains binaries, libraries, documentation, and source-code for second level programs.

It contains Variable data information (Ex: – Log Files, Mail Spool Information).

It contains Super Users home directories information.

It contains all kernel related running process information.


Concepts of Kernal & Shell


The kernel is a program that constitutes the central core of a computer operating system. It has complete control over everything that occurs in the system. A kernel can be contrasted with a shell (such as bash, csh or ksh in Unix-like operating systems), which is the outermost part of an operating system and a program that interacts with user commands. The kernel itself does not interact directly with the user, but rather interacts with the shell and other programs as well as with the hardware devices on the system, including the processor (also called the central processing unit or CPU), memory and disk drives.

Interacts with the hardware
First program to get loaded when the system starts and runs till the session gets terminated
Different from BIOS which is hardware dependent.
Kernel is software dependent

Types of Kernals
All OS related code are stuffed in a single module
Available as a single file
Faster functioning

OS components are isolated and run in their own address space
Device drivers, programs and system services run outside kernel memory space
Supports modularity
Lesser in size

Shell is a UNIX term for the interactive user interface with an operating system. The shell is the layer of programming that understands and executes the commands a user enters. In some systems, the shell is called a command interpreter.

Program that interacts with kernel
Bridge between kernel and the user
Command interpreter
User can type command and the command is conveyed to the kernel and it will be executed

Types of Shells

simple shell

Bourne Again Shell

Korne Shell

C Shell

Secure Shell