Slide 1: A mini- project on linux
operating system Slide 2: CONTENTS
HISTORY OF LINUX
MEMORY MANAGEMENT Slide 3: INTRODUCTION OF LINUX To over come the disadvantages and break troughs of
windows & Windows vista the first version of
LINUX (LINUX 1.0) is been bought up in 1991
Lets see the architecture of LINUX and its various
features ---? Slide 4: LINUX Developed by LINUX TORVALDS in 1991 .1st version –
Freely distributed- open source.
FUNCTIONALITY,ADAPTABILITY & ROBUSTNESS –main
alternative to UNIX & MICROSOFT OS. Slide 5: VERSIONS: Debian based.
Ubuntu based official distributions.
Red-hat –enterprise LINUX- based. Slide 6: BOOTING PROCESS Computer power- BIOS procedure.
BOOT LOADER- invokes BIOS to load OS kernel into
RAM Slide 8: LINUX KERNELS:
Linux kernel is monolithic.
Traditional UNIX kernels are compiled & linked
Multilevel application support.
LINUX is a non-pre emptive kernel.
Multiprocessor support. Slide 9: ARCHITECTURE Kernel layer is integrated & runs in kernel mode. Slide 10: SEMAPHORES: Used to implement threads.
A counter DS.
decrements the semaphore value.
increments the semaphore value. Slide 11: PROCESS MANAGEMENT PROCESS:
Fundamental to multiprogramming os.
Instance of program in execution
Creation of process-fork().
Termination of process-exit(). Slide 12: PROCESS STATES TASK_RUNNING
TASK_ZOMBIE Slide 13: PROCESS SWITCHING:
Also called CONTEXT SWITCHING.
To control the execution of process ,kernel suspends
execution of process RUNNING and resumes the execution
of some other process previously suspended Slide 14: KERNEL THREAD –DISTINGUISHING FACTORS:
Executes single specific kernel function.
Whereas others through system call
Kernel threads run only in kernel mode.
Whereas others through in kernel & user mode Slide 15: MEMORY MANAGEMENT
Abstraction acts as logical layer between
Application request and MMU. Slide 16: ADVANTAGES:
Several processes can be executed concurrently.
Possible to run application whose memory
needs >available memory
Relocatablity i.e. can be placed any where
Programmers need to write only machine- independent code
Memory fragmentation. Slide 17: MEMORY ADDRESSING
Uses three addresses:
SEGMENTATION UNIT TRANSFORMS
Logical address --? linear address
PAGING UNIT TRANSFORMS
Linear address-? physical address Slide 18: SEGMENTATION UNIT:
Segment register holds segment selector or
identifier. Slide 19: TRANSLATION LOOKASIDE BUFFERS (TLB):
To speed linear address translation.
Linear address when used for one time, physical address is
computed through page tables and stored in TLB.
Further references can be quickly found. Slide 20: PAGE TABLES:
Page global directory
Page middle directory
Paging ensures efficient protection against addressing error.
Distinguish pages from page frames (Basic ingredient of
VM mechanism). Slide 21: MEMORY AREA MANAGEMENT:
Better use of cache.
Lower average memory access times.
Suffers internal fragmentation.
Avoids external fragmentation
Disadvantage is fiddle through page tables. Slide 22: DEMAND PAGING:
Denotes a dynamic memory allocation techinque that
of differing page frame allocation until the last
Page fault occurs when we attempt to address a page
that is not in RAM.
Only a small subset of the process pages are referenced.
Preferable to global allocation.
Increases average number of free page frames.
Better throughput. Slide 23: SYNCHRONISATION TECHNIQUES:
To avoid race conditions among processes.
Non preemptability of processes in kernal mode.
Locking.. Slide 24: SWAPPING:
Kernel uses some space on disk as an extension of RAM.
It is transparent to the programmer.
Abstraction of availability of physical memory.
Extends amount of addressable memory at the expense of
access speed Slide 25: SWAPPING BENEFITS:
To extend the address space that is effectively usable
by a process
To expand the amount of dynamic RAM to load
process. Slide 26: ISSUES TO BE CONSIDERED DURING SWAPPING:
Which kind of page to swap out.
How to distribute pages in the swap area.
How to select the page to be swapped out.
When to perform the swap out. Slide 27: I/O MANAGEMENT:
Data paths are provided for information flow between CPU,RAM,
Data paths are collectively known as bus, which are the primary
Bus types: ISA,EISA.PCI,MCA.
CONTROL BUS Slide 28: I/O PORTS & INTERFACES:
Every device connected to I/O bus has its own set of I/O address,
which are I/O ports.
Interface is a circuit inserted between a group of I/O ports and
the corresponding device controller.
Acts as an interpreter to translate value in I/O ports into
commands. Slide 29: DEVICE CONTROLLERS:
A complex device may require a device controller to
It interprets the highly-level commands and executes
Converts and properly interprets the electrical signals
received from the device. Slide 30: DMA-DIRECT MEMORY ACCESS
Auxillary processor to transfer data between RAM and
Once activated , takes its own control to transfer.
Memory arbiter controls the conflicts occuring when
both CPU & DMCA need to access the same memory
location. Slide 31: LEVEL OF KERNAL SUPPORT:
No support at all.
TECHNIQUES TO MONITOR I/O OPERATION:
Interrupt mode. Slide 32: FILE MANAGEMENT
A UNIX file is an info container structured as a
Length of file system is 255 characters.
Directory corresponding to root is root directory
denoted by /.
Same name cannot be used for different
Pathname is used to identify a specific file. Slide 33: Difference from other os: Linux is free of cost
Runs on low-end ,cheap platforms.
Kernel is very small & compact.
Well supported. Slide 34: FILE TYPES
Block oriented device file.
Pipe & named pipe
(also called FIFO)
socket Slide 35: FILE HANDLING SYSTEM CALLS:
A process in user mode cannot directly interact with
low –level h/w components.
Therefore each actual file operation must be performed
In kernel mode.
To prevent this UNIX os defines system call.
Is used & file pathname is passed as parameter.
Eg: To access a file ,open the file using system call.
fd=open(path ,flag ,mode)
path ?denotes path name of opened file
flag ?specifies how file must be opened
mode ?specifies the access rights of created file. Slide 36: VIRTUAL FILE SYSTEM : VFS
Linux manages to support multiple disk type in same way as
UNIX variants do ,through a concept called VFS
VFS is a kernel software layer that handles all system calls
related to standard UNIX file system.
Its main strength is providing a common interface to several
kind of file systems.
It allows you to transparently mount different file systems at
On implementing Linux VFS ,access to the files is as fast &
efficient as possible. Slide 37: VFS INODE
Every file & directory in VFS is represented by only one VFS
The info in each VFS node is built from information. In file
system by specific file system routines.
It exists only in kernel’s memory & uses cache.
It contains following fields:
Dirty Slide 38: NETWORK MANAGEMENT IN LINUX
Mission maintaining availability of resources such as ROUTERS,
HUBS,SERVERS and Etc..
Network of an organization includes WAN or INTERNET.
Other links, link point to point or frame relay are charged on
a flat rate. Slide 39: SNMP-SIMPLE NETWOK MANAGEMENT PROTOCOL
Aim was to integrate the management of different n/w with
simple design that causes very little stress on the n/w.
Uses TCP/IP transport protocol.
ELEMENTS IN SNMP:
Performs deal with fetch & store paradigm.
Request or set value of variable in MIB of the agent. Slide 40: SECURITY:
Supports two password schema called communities.
Allows manager to request value of variables.
Allows these values to be set.
If IP Routing between two devices fails , its impossible to reach
the target to monitor or reconfigure it. Slide 41: A SIMPLE PROCESSSING OF FILES IN LINUX This is how the process is
moduled and scheduled and
this diagram shows the
simple path of processing Slide 42: SECRET OF LINUX LOGO Once Linus went to the southern hemisphere
on a vacation. There he encountered a penguin,
not unlike the current logo of Linux.
As he tried to pat it, the penguin bit his hand.
This amusing incident led to the selection of
a penguin as the logo of Linux sometime later Slide 43: SEE THE USER SCREEN OF LINUX
PALM TOP ----? Slide 45: WHY TO USE THE LINUX AS YOUR
OPERATING SYSTEM….? HACKING IS NOT ALL POSSIBLE WHEN A SYSTEM IS RUNNING
IN LINUX OPERATING SYSTEM
DATA SECURITY AND SYSTEM SECURITY IS WELL CONCERNED
FREE OF COST
NO MALWARE OR VIRUS THREATS COULD BE FOUND IN
LINUX Slide 47: QUERRIES……..? Slide 48: Mini – Project on operating system BY
2.) V.VIGNESH KUMAR
4.) K.M.SARAVANA PRABHU 4th SEM B.Sc CT-G1