Linux Environment- Linux Basics Operating System Introduction to Linux What is Shell? What is Shell Script

1. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Affiliated Institution of G.G.S.IP.U, Delhi
BCA
Linux Environment
BCA306
Linux Basics
Keywords: Linux, Unix, Characteristics
and Architecture

2. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
An operating system is the software that
provides the interface between the hardware
of a computer system and the applications
programs that are used on it.

3. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Introduction to Linux
• A free Unix-type operating system originally created by
Linus Torvalds with the assistance of developers around
the world.
• The source code for Linux is freely available to everyone.
• Has the X Windows GUI , including many of the tools
that Windows users are familiar with such as,
– A file manager
– A Window manager
– A help system
– A configuration
– …….

4. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
• Requiring less system resources. A Linux based system can
operate smoothly on a 386 or 486.
• Application software support
– Office applications: Corel WordPerfect Office 2000 for
Linux Deluxe
– Graphics tool: Gimp
– Browsers: Netscape Communicator 4.75, Opera browser
• Multi-user, Multitasking, Multiprocessor
• Coexists with other Operating Systems
• Runs on multiple platforms
Introduction to Linux . . contd

5. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Main Characteristics
• Multitasking
– Linux supports true preemptive multi-tasking. All processes run
independently of each other.
• Multi-user access
– Linux allows number of users to work with the system at the
same time.
• Multi-processing
– Operating system can distribute several applications across
several processors.
• Architecture Independence
– Linux can run on several hardware platforms from amiga to PC
to DEC Alpha workstations.

6. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Main Characteristics
• Demand load executables
– Only those parts of a program actually required for execution
are loaded into memory.Copy-on-write principle is used when
a new process accesses memory in write mode.
• Paging
– Linux uses paging to use the physical memory efficiently.
• Dynamic cache for hard disk
– Linux dynamically adjusts the size of cache memory in use to
suit the current memory usage situation.
• Shared Libraries
– Libraries are collection of routines needed by a program for
processing data. They are loaded into memory only when the
process is run.

7. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Main Characteristics
• Support for POSIX 1003.1(Portable Operating System Interface for
Unix) standard
– POSIX 1003.1 defines a minimum interface to a unix type
operating system. Linux fully supports it
• Various formats for executable files
– Linux can execute programs from other unix system conforming
to iBCS2(Intel Binary Compatibility Standard (ibcs2))
standard.
• Memory protected Mode
– Linux uses processor’s memory protection mechanisms to
prevent the process from accessing memory allocated to system
kernel or other processes.
• Support for national keyboards, fonts

8. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
Main Characteristics
• Different file systems
– Linux supports variety of file systems. Most common being
Second extended (ext2) file system. Others being ms-dos file
system, VFAT file system for accessing windows/ms-dos,ISO
for accessing CD-ROMS, NFS for accessing the file systems
of other unix systems etc.
• TCP/IP, SLIP and PPP support
– Linux can be integrated into local unix networks. All network
services, such as NFS and remote login can be used. SLIP and
PPP support the use of TCP/IP protocol over serial lines i.e.
internet via pubic telephone network.

9. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
- Surrounding the kernel and acting as a user interface to the Linux
operating system
- Command language interpreter
- Interprets the command users enter
- Selects and runs the command or program
- Provides the results to the screen or file as
directed by the command
-C shell, Bourne shell, Korn shell
Linux functionally organized at three levels
shell
Tools and applications
The main part of operating system, and responsible for
controlling system resources.
-Loaded into memory when the system boots
-Process control and scheduling
-Memory management
-Device I/O
-System error handling
-User programs requesting services from the kernel through
system calls
-Hardware devices getting kernel response through interrupts
kernel
offering additional
functionality to the operating
system

10. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
What is Kernel?
Kernel is heart of Linux Os.
It manages resource of Linux Os. For e.g. Facility to
store data, print data on printer, memory, file
management etc .
Kernel decides who will use this resource, for how
long and when. It runs your programs (or set up to
execute binary files).
The kernel acts as an intermediary between the
computer hardware and various
programs/application/shell

11. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
What is Shell?
An interface between the Linux system and the user
• Used to call commands and programs
• An interpreter
• Many available (bsh; ksh; csh; bash; tcsh)
• A shell is any program that takes input from the user,
translates it into instructions that the operating
system can understand, and conveys the operating
system's output back to the user.

12. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
What is Shell Script ?
Shell Script is series of commands written in
plain text file.
 Shell script can take input from user, file and
output them on screen.
 Useful to create our own commands.
 Save lots of time.
 To automate some task of day today life.
 System Administration part can be also
automated.

13. TRINITY INSTITUTE OF PROFESSIONAL STUDIES
Sector – 9, Dwarka Institutional Area, New Delhi-75
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