Network operating systems

Network Operating System
By: Mr. Sachin Awasthi
Department of MCA
Govt. PG College Dharamshala
E-mail: sachinawasthi025@gmail.com
Mobile:+91-9882561161Mobile:+91-9882561161

 Introduction to Operating System
(OS)
Operating Systems

 A modern computer consists of:
 One or more processors
 Main memory
 Disks
 Printers
 Various input/output devices.
 Managing all these varied components requires a
layer of software – the
Operating System (OS).
What is an Operating System?

 An Operating System is a program that acts as an
intermediary/interface between a user of a
computer and the computer hardware.
 OS goals:
– Control/execute user/application programs.
– Make the computer system convenient to use.
– Ease the solving of user problems.
– Use the computer hardware in an efficient
manner.
What is an Operating System?

 Facilities for program creation
– editors, compilers, linkers, debuggers, etc.
 Program execution
– loading in memory, I/O and file initialization.
 Access to I/O and files
– deals with the specifics of I/O and file formats.
 System access
– resolves conflicts for resource contention.
– protection in access to resources and data.
Services provided by an OS

 Hardware – provides basic computing resources (CPU,
Memory, I/O devices, Communication).
 Operating System – controls and coordinates
use of the hardware among various application programs
for various users.
 System & Application Programs – ways in which the
system resources are used to solve computing problems
of the users (Word processors, Compilers, Web
browsers, Database systems, Video games).
 Users – (People, Machines, other computers).
Computer System Components

Computer Hardware Organization

User 1 User 2 User 3 User n
System and Application Programs
Operating System
Computer Hardware
Compiler Assembler Text editor Databases
System
........
Figure: Abstract view of the components of a computer system

Views of an Operating System
 There are three classical views (in literature):
1. Resource Manager – manages and allocates resources.
2. Control program – controls the execution of user
programs and operations of I/O devices.
3. Command Executer – Provides an environment for
running user commands.
 But one more modern view: the Operating System as a
Virtual Machine.

1. Resource Manager
 Resource Manager:
– Manages and protects multiple computer resources: CPU,
Processes, Internal/External memory, Tasks, Applications,
Users, Communication channels, etc…
– Handles and allocates resources to multiple users or
multiple programs running at the same time and space
(e.g., processor time, memory, I/O devices).
– Decides between conflicting requests for efficient and fair
resource use (e.g., maximize throughput, minimize
response time).

OS as a Resource Manager
A. Frank - P. Weisberg

2. Control Program
 Control Program:
– Manages all the components of a complex computer system
in an integrated manner.
– Controls the execution of user programs and I/O devices to
prevent errors and improper use of computer resources.
– Looks over and protects the computer: Monitor,
Supervisor, Executive, Controller, Master, Coordinator ….

3. Command Executer
 Command Executer:
– Interfaces between the users and machine.
– Supplies services/utilities to users.
– Provides the users with a convenient CLI (Command
Language Interface), also called a Shell (in UNIX), for
entering the user commands.

Evolution of OS:
 The evolution of operating systems went through seven
major phases.
 Six of them significantly changed the ways in which
users accessed computers through the open shop, batch
processing, multiprogramming, timesharing, personal
computing, and distributed systems.
 In the seventh phase the foundations of concurrent
programming were developed and demonstrated in
model operating systems.


Evolution of OS (contd..):
Major Phases Technical
Innovations
Operating
Systems
Open Shop The idea of OS IBM 701 open shop
(1954)
Batch Processing Tape batching,
First-in, first-out
scheduling.
BKS system (1961)
Multi-
programming
Processor multiplexing,
Indivisible operations,
Demand paging,
Input/output spooling,
Priority scheduling,
Remote job entry
Atlas supervisor
(1961),
Exec II system (1966)

Evolution of OS (contd..):
Timesharing Simultaneous user
interaction,
On-line file systems
Multics file system
(1965),
Unix (1974)
Concurrent
Programming
Hierarchical systems,
Extensible kernels,
Parallel programming
concepts, Secure
parallel languages
RC 4000 system
(1969),
13 Venus system
(1972),
14 Boss 2 system
(1975).
Personal
Computing
Graphic user interfaces OS 6 (1972)
Pilot system (1980)
Distributed
Systems
Remote servers WFS file server
(1979) Unix United
RPC (1982)
24 Amoeba system
(1990)

Batch Processing:
 In Batch processing same type of jobs batch (BATCH- a set
of jobs with similar needs) together and execute at a time.
 The OS was simple, its major task was to transfer control
from one job to the next.
 The job was submitted to the computer operator in form of
punch cards. At some later time the output appeared.
 The OS was always resident in memory.
 Common Input devices were card readers and tape drives.

Batch Processing (Contd…):
 Common output devices were line printers, tape drives,
and card punches.
 Users did not interact directly with the computer
systems, but he prepared a job (comprising of the
program, the data, & some control information).
OS
User
program
area

Multiprogramming:
 Multiprogramming is a technique to execute number of
programs simultaneously by a single processor.
 In Multiprogramming, number of processes reside in main
memory at a time.
 The OS picks and begins to executes one of the jobs in the
main memory.
 If any I/O wait happened in a process, then CPU switches
from that job to another job.
 Hence CPU in not idle at any time.

Multiprogramming (Contd…):
OS
Job 1
Job 2
Job 3
Job 4
Job 5
• Figure dipicts the layout of
multiprogramming system.
• The main memory consists of 5
jobs at a time, the CPU executes
one by one.
Advantages:
•Efficient memory utilization
•Throughput increases
•CPU is never idle, so performance
increases.

Time Sharing Systems:
 Time sharing, or multitasking, is a logical extension of
multiprogramming.
 Multiple jobs are executed by switching the CPU between
them.
 In this, the CPU time is shared by different processes, so it is
called as “Time sharing Systems”.
 Time slice is defined by the OS, for sharing CPU time
between processes.
 Examples: Multics, Unix, etc.,

Types of OS:
Operating System can also be classified as,-

Real Time OS
RTOS are used to control machinery, scientific
instruments and industrial systems. An RTOS typically
has very little user-interface capability, and no end-user
utilities, since the system will be a "sealed box" when
delivered for use. ™A very important part of an RTOS
is managing the resources of the computer so that a
particular operation executes in precisely the same
amount of time, every time it occurs. ™In a complex
machine, having a part move more quickly just because
system resources are available may be just as
catastrophic as having it not move at all because the
system is busy.

Single User Single task
As the name implies, this operating system is designed to
manage the computer so that one user can effectively do one
thing at a time.
Example of single user OS are
MS-DOS.
The Palm OS for Palm handheld computers is a good example
of a modern single-user, single-task operating system.

Single User multi tasking
This is the type of operating system most people use on their
desktop and laptop computers today.
Examples of Single user multi tasking are:
Microsoft's Windows and Apple's MacOS platforms are both
examples of OS that will let a single user have several
programs in operation at the same time. ™ For example, it's
entirely possible for a Windows user to be writing a note in a
word processor while downloading a file from the Internet
while printing the text of an e-mail message.

Multi user
A multi-user operating system allows many different users to
take advantage of the computer's resources simultaneously.
™The operating system must make sure that the requirements
of the various users are balanced, and that each of the
programs they are using has sufficient and separate resources
so that a problem with one user doesn't affect the entire
community of users.
Examples of Multiuser Os are:
™Unix, VMS and mainframe operating systems, are examples
of multi-user operating systems.

What is a Network?
 is a communication path between two or more systems
 vary by the protocols used, the distances between nodes,
and the transport media
 TCP/IP is the most common
network protocol

Need for Networks
 Enhance communication.
 Share resources.
 Facilitate centralized management.

Classification of Networks
 Classification by network geography.
 Classification by component roles.

Classification by Network
Geography
 Networks are frequently classified according to the
geographical boundaries spanned by the network itself.
 LAN, WAN, and MAN are the basic types of
classification, of which LAN and WAN are frequently
used.

Classification by Component Roles
 Networks can also be classified according to the roles
that the networked computers play in the network’s
operation.
 Peer-to-peer, server-based, and client-based are the
types of roles into which networks are classified.

Peer-to-peer:
In a peer-to-peer network, all computers are considered
equal. Each computer controls its own information and is
capable of functioning as either a client or a server
depending upon the requirement.
Peer-to-peer networks are inexpensive and easy to install.
They are popular as home networks and for use in small
companies.

Peer-to-peer (continued):
– Most operating systems come with built-in peer-to-
peer networking capability.
– The maximum number of peers that can operate on a
peer-to-peer network is ten.
– Each peer shares resources and allows others open
access to them.

Peer-to-peer (continued):
– Peer-to-peer networks become difficult to manage
when more security is added to resources, since the
users control their security by password-protecting
shares.
– Shares can be document folders, printers, peripherals,
and any other resource that they control on their
computers.

Peer-to-peer network

Server-based:
– A server-based network offers centralized control
and is designed for secure operations.
– In a server-based network, a dedicated server
controls the network.

Server-based (continued):
– A dedicated server is one that services the network
by storing data, applications, resources, and also
provides access to resources required by the client.
– These servers can also control the network’s
security from one centralized location or share it
with other specially configured servers.

Server-based network

Client-based:
– Client-based network servers process requests from
clients and return just the results.
– These networks take advantage of the powerful
processing capabilities of both the client and the
server.
– Application servers and communications servers are
examples of client-based networks.

Client-based network

 Provides an environment in which users, who are aware of
multiplicity of machines, can access remote resources
either:
-> logging in to the remote machine* or
-> transferring data from the remote
machine to their own machines
 mostly used with local area networks and widearea
networks
*Remote machine: refers to a computer connected to the
network which a user is using.

Features
 Provides basic operating system features; support for
processors, protocols, automatic hardware detection,
support multi-processing of applications
 Security features; authentication, authorization, access
control
 Provides names and directory services
 Provides files, print, web services, back-up and replication
services

 Supports Internetworking such as routing and WAN ports
 User management and support for login and logoff, remote
access, system management
 Clustering capabilities, fault tolerant and and high
availability systems
Cluster: = group of linked computers working together
closely, connected to LAN

Network and Operating System Security
 OS: system must protect itself
 Runway process could constitute an accidental denial-of-
service attack
 Query to service could reveal passwords
 Stack overflow could allow the launching of an
unauthorized process
 List of possible breaches is almost endless

 Travels over private leased lines, shared lines like the
internet, wireless connections, or dial-up lines
 Intercepting these data could be harmful as breaking into a
computer
 Interruption of communications could constitute a remote
denial-of-service attack,
diminishing user‘s use of
and trust in the system

What is Unix?
 A multi-task and multi-user Operating System
 Developed in 1969 at AT&T’s Bell Labs by
– Ken Thompson (Unix)
– Dennis Ritchie (C)
– Douglas Mcllroy
 Some other variants: System V, Solaris, SCO Unix,
SunOS, 4.4BSD, FreeBSD, NetBSD, OpenBSD, BSDI

What is Linux?
 A clone of Unix
 Developed in 25 August 1991 by Linus Torvalds, a Finish
graduate student
 Inspired by and replacement of Minix
 Linus' Minix became Linux
 Consist of
– Linux Kernel
– GNU (GNU is Not Unix) Software
– Software Package management
– Others

Linux
 Linux is a generic term referring to Unix-like graphical
user interface (GUI) based computer operating systems.
 It is Multi-user, Multitasking, Multiprocessor
 Has the X Windows GUI
 Coexists with other Operating Systems
 Runs on multiple platforms
 Includes the Source Code

Which Linux Distribution is
better?
 > 300 Linux Distributions
– Slackware (one of the oldest, simple and stable distro.)
– Redhat
• RHEL (commercially support)
• Fedora (free)
– CentOS (free RHEL, based in England)
– SuSe ( based in German)
– Gentoo (Source code based)
– Debian (one of the few called GNU/Linux)
– Ubuntu (based in South Africa)
– Knoppix (first LiveCD distro.)
– …

Advantages and disadvantages of
Linux
Advantages
 Cost
 Security
 Choice
 Flexibility
 Hardware
Disadvantages
 Understanding
 Compatibility

Linux Users and Groups
Management

Introduction
 Ubuntu Linux uses groups to help you manage users,
set permissions on those users, and even monitor how
much time they are spending in front of the PC.
 Normally Linux computers have two user accounts—
your own user account, and the root account, which is
the super user that can access everything on the PC,
make system changes, and administer other users.
Ubuntu works a little differently, though—you can’t
login directly as root by default, and you use
the sudo command to switch to root-level access when
you need to make a change.

How Linux User Accounts
Work
 Linux stores a list of all users in the ‘/etc/groups’ file.
You can run this command in the Terminal to to view and
edit the groups and users in your system:
– sudo nano /etc/groupssudo nano /etc/groups

How Linux User Accounts
Work
 Username
 Password

By default, all user home directories are created and
maintained in the /home
directory.

However, the root user’s home directory is /root

User Accounts storage
• Local This option stores user accounts in the
/etc/passwd file. This has been the default configuration
used by Linux systems for many years.
– /etc/passwd This file contains the user account
information for your system.
– /etc/shadow This file contains passwords for your user
accounts.
– /etc/group This file contains your system’s groups

The Superuser
 Must limit use of root
– Inexperienced users can cause serious harm
– Use of root for non-privileged tasks unnecessary and
can be open to attack
– Security and privacy violations – root can look at
anyone’s files
 Limit what root can do remotely
 Ensure a strong password

Superuser Privileges
 What usually works best is short periods of superuser
privilege, only when necessary
 Obtain privileges, complete task, relinquish privileges
 Most common ways are su and sudo
 Can also use the setuid/setgid method, but not
recommended

Other permissions models
 Some Linux distributions such as Ubuntu obscure
away the root account altogether
 By default the end user doesn’t know the root
password
– Can’t login as root
– Can’t su
 Must rely on sudo (and the graphical gksudo) to
obtain privilege, along with ‘Unlock’ functions in
GUI

Creating and Managing User
Accounts
 Using useradd
 Using passwd
 Using usermod
 Using userdel

Using useradd
Syntax: useradd options username
example: useradd ken
ken account is created using the default parameters
contained in the following configuration files:
/etc/default/useradd
/etc/login.defs This file contains values that can be used
for the GID and UID parameters when creating an
account with useradd.
It also contains defaults for creating passwords in
/etc/shadow.

Using userdel
 Syntax: userdel username
 example: userdel ken
It’s important to note that, by default, userdeluserdel will not
remove the user’s home directory from the file
system. If you do want to remove the home
directory when you delete the user, you need to use
the –r option in the command line. For example,
entering userdel –r kenuserdel –r ken will remove the account and
delete her home directory.

Managing groups
 Using groupadd
 Using groupmod
 Using groupdel
 groups are defined in the /etc/group file. Each
record is composed of the following four fields:
Group:Password:GID:Users
 Group Specifies the name of the group. In the
example above, the name of the group is video.
 Password Specifies the group password.

Managing groups
 GID Specifies the group ID (GID) number of the
group.
 Users Lists the members of the group.
 As with /etc/shadow, each line in /etc/gshadow
represents a record for a single group. Each record is
composed of the following fields:
Group_Name:Password:Group_Admins:Group_Me
mbers

Using groupadd
 Syntax:
groupadd options groupname
 Options:
–g Specifies a GID for the new group.
–p Specifies a password for the group.
–r Specifies that the group being created is a system
group

Using groupdel
Syntax: groupdel group_namegroup_name
example: groupdel studentstudent

Managing ownership
Anytime a user creates a new file or directory, his
or her user account is assigned as that file or
directory’s “owner.” For example, suppose the ken
user logs in to her Linux system and creates a file
named linux_introduction.odt using OpenOffice.org
in home directory. Because she created this file, ken
is automatically assigned ownership of
linux_introduction.odt.

Using chown
 The chown utility can be used to change the user or group that
owns a file or directory.
Syntax chown user.group file or directory.
Example: If I wanted to change the file’s owner to the ken1 user, I
would enter
chown ken1 /tmp/myfile.txt
–If I wanted to change this to the users group, of which users is a
member, I would enter
chown .users /tmp/myfile.txt
Notice that I used a period (.) before the group name to tell chown
that the entity specified is a group, not a user account.
Ex: chown student.users /tmp/myfile.txt
Note: You can use the –R option with chown to change ownership
on many files at once recursively.

Using chgrp
 In addition to chown, you can also use chgrp to change
the group that owns a file or directory.
 Syntax: chgrp group file (or directory)
 Example: chgrp student /tmp/newfile.txt.

Difference between Operating System and
 OS runs the computer itself
Example: Windows
 Network OS run on a server
and can be accessed
through client machines
connected on the network
Example: Novell Netware
and Linux run on a server
and can be used as NOS,
even there are Windows
server OS‘s which can be
used by clients connected on
the network

Download Ubuntu 14.10, put the CD on the CD
ROM drive, change the boot sequence accordingly,
so that CD ROM can boot first and select the
language of your choice and than press Enter.

Partition scheme will be like below:
/boot – 100MB
swap – 2048MB
/ – Remaning (19GB)
Select free space and click on + sign at the bottom to create
partitions. Following shows for /boot partition.

Installation of Windows NT
 Windows NT 4.0 (NT stands for New Technology) was a
32 bit closed source operating system released on 31st July
1996 orientated at business users. It had a similar interface
to Windows 95. The operating system succeeded Windows
NT 3.51 but was succeeded by Windows 2000. The NT
family still lives on all Microsoft operating systems from
Windows XP onwards. This article will show you how to
install Windows NT 4.0 Workstation.

Press F8 To accept the terms and
conditions

Select the partitioning of your hard drive that you want to
install Windows NT 4.0 on and press Enter.↵ (The
instructions will show you what to do on an unpartitioned
hard drive).

After Selecting and Formatting the hard drive windows will
ask you to where to store the files

 After this we will have to set the various preferences and
your system reboots. Make sure you have to repeatedly
press F8 otherwise it will repeat installation.

Wait for screen to pop up and
than press next

 Choose the type of setup you want and click Next.It's a
matter of personal preference but for this tutorial, we will
be using the 'Typical' setup which is a Microsoft default
setup.

Type your name and/or your organisation
and click Next.

Type in a name for your computer
(can be anything) and click Next.

 Than choose your network and
component preferences and than click
finish. Your Computer is now act as
server. And the system will be starts by
pressing ctrl+alt+delete.

Summary
 NOS provides features such as file sharing across the network
 Includes communication scheme
 Allows different processes on different computers to exchange
messages
 Computer running a NOS acts autonomously from all other
computers on the network
 It is aware of the network – able to communicate with other
networked computers

Network operating systems

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