The document provides an overview of the Linux operating system, including its history, design principles, components, and key features. It discusses the kernel, processes and threads, scheduling, memory management, file systems, I/O, inter-process communication, networking, and security in Linux. The document is intended to introduce the fundamental concepts and architecture of the Linux system.

1. 11-1
THE LINUX SYSTEM
DesigneD by:
Nilesh Jaiswar
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2. 11-2
INDEX
• History
• Design principals
• Components of linux system
• Kernel modules
• Process management
• Process and threads
• Scheduling in linux
• Process scheduling
• Memory management
• File systems
• I/O in linux
• Interprocess communication
• Linux networking structure
• Security
• Conclusion

3. 11-3
HISTORY

4. 11-4
DESIGN PRINCIPLES
 LINUX: A Multitasking, Multiuser and
full set of UNIX compatible tools.
It is capable of operating under 4Mb of
RAM
It contains POSIX standards.
It act as a interface for both the
programmer and the user.

5. 11-5
USER INTERFACE
Users operate linux through CLI and
GUI.
On desktop systems: KDE Plasma
Desktop,GNOME and Xfce.
Linux kernel and other components are
free and open source software.

6. 11-6
COMPONENTS OF LINUX SYSTEM
Linux system consists of three main bodies:
• The kernel
• The system libraries
• The system utilities

7. 11-7
KERNEL MODULES
Three components of the module:
• Module management
• Driver Registration
• Conflict Resolution

8. 11-8
PROCESS MANAGEMENT
Two different operations:
•The creation of process
•Running of new program
Terms in linux:
•Fork-a new process is created by fork system call.
•Execve-a new program is run after a execve call
•Clone-creates a new process sharing parent data structure
having it’s own identity.

9. 11-9
PROCESS MANAGEMENT
Process properties:
• Process identity:
a. Process ID(PID):
b. Credentials:
c. Personality:
• Process environment:
• Process context:
a. Scheduling context:
b. Accounting:
c. File table:
d. File system context:
e. Single handler table:
f. Virtual memory context:

10. 11-10
Processes and Threads
• Threads are light weight processes(LWPs)
• Processes are heavy weight processes(HWPs)
• Fundamental parts of process:
a. code(text)
b. data(vm)
c. stack
d. file I/O
e. signal table
• Threads: user level and kernel level

11. 11-11
PROCESSES AND THREADS
1. REPRESENT THE EXECUTION
OF SINGLE
PROGRAM
2. TWO SEPARATE
PROCESSES WILL HAVE
THEIR OWN INDEPENDENT
ADDRESS SPACE
1. REPRESENT SEPARATE ,
CONCURRENT EXECUTION
WITHIN SINGLE PROCESS
2. TWO THREADS WITHIN A
PROCESS SHARE SAME
ADDRESS SPACE

12. 11-12
SCHEDULING
• The linux scheduler is a pre-emptive , priority-based
algorithm
• Two separate priority ranges :
1. Real-time range( 0 to 99)
2. ice-value range (100 to 140)
• Once kernel code start running , then it is the only kernel
code till the following event occurs.
1. An interrupt
2. A page fault
3. A kernel code call to the scheduler function itself

13. 11-13
PROCESS SCHEDULING
Linux supports two process scheduling algorithms
• Time- sharing algorithm
• Real- time task algorithm
1.First-in first-out (FIFO)
2.Round Robin

14. 11-14
MEMORY MANAGEMENT
Two components in Memory management:
• Physical memory management
• Virtual memory
Physical memory management: This deals with allocation
and deallocation of pages, group of pages and blocks of memory.
Virtual memory: it is the memory mapped into the address
space of running process.

15. 11-15
PHYSICAL MEMORY MANAGEMENT
•Physical memory manager is a page allocator, which uses
“buddy heap” algorithm in order to keep track of available address
space .
Ex. Splitting of memory in buddy heap.
16 KB
8KB
8 KB
8 KB
4 KB
4 KB

16. 11-16
VIRTUAL MEMORY
• Virtual memory is responsible for maintaining the address
space visible to each process.
• There are two situations where the kernel creates a new
virtual address space
a) when a process runs a new program with the “exec”
system call.
b) When a new process is created by the “fork” system call.

17. 11-17
FILE SYSTEMS
• Linux file system retains UNIX’s features. here file can
be anything capable of handling I/O of stream of data.
• The virtual file system is designed using object oriented
principles. It consists of two components,
i. A set of definition which define what a file object is
allowed to look like.
ii. A layer of software to manipulate those objects.
3 main object defined by VTS are
i. Inode object
ii. File object structure
iii. File system object

18. 11-18
I/O IN LINUX
Linux splits all the I/O devices into three groups
a. Block devices
b. Character devices
c. Network devices
• Block devices include all devices that allow random
access like HDD, floppy disk & CD-ROMS.
• Character devices include other devices with the main
exception of network devices like Magnetic tap devices.
• Network devices are dealt differently from both devices.
user cannot transfer directly data to network devices
but communicate indirectly. Ex. Tty discipline.

19. 11-19
Inter-Process Communication
VARIOUS types of MECHANISM
• SIGNAL
• PIPES
• FISOS
• Message Queues
• Semaphores
• Shared Memory

20. 11-20
LINUX NETWORK STRUCTURE
Linux kernel is implemented using the
three layers of software internally-
• System call interface
• Protocol agnostic interface
• Network protocols

21. 11-21
SECURITY
In Linux, Security issues can be
classified in two group-
• AUTHENTICATION
• ACCESS CONTROL

22. 11-22
Conclusion
“When is it best to use Linux and when
should some other operating system be
preferred?”
It all depends on the user

23. 11-23
REFERENCES
•www. Wikipedia.com
•www.trimble.com
•www.wiley.com
•Book: Operating system concepts