14-08-2012, 01:33 PM
PROCESS MANAGEMENT IN LINUX
Process Management In Linux 1.ppt (Size: 3.09 MB / Downloads: 41)
INTRODUCTION TOPROCESSES
Whenever a Developer writes,compiles and links a programme it may be stored on a computer disk as a disk file system.This file is created in a predefined format that the operating system or operating system shell will recognise as an executable programme.
A Process may operate in one of two modes which are known as ‘USER MODE’ and ‘SYSTEM MODE’(KERNEL MODE).
A USER processes switches to KERNEL MODE when it makes a system call,generates an fault or when interrupt occurs.At this point the KERNEL is executing on behalf of the process.
Processes operating in KERNEL MODE are privileged and are granted access to all computer resources free of the restrictions applied to USER MODE.
Definition Of Process
A Process is the basic context within which all user-requested activity is serviced within the operating system.
TYPES OF PROCESSES-
1} Interactive processes
2} System processes
Interactive processes are those processes that are invoked by a user and can interact with the user
System processes is term used to refer the process that are running on the computer and provide services but do not interact with the console.
PROCESS ID or (PID):-
Process ids (or PIDs) are 32-bit numbers, also used to identify processes.
PIDs are used to specify processes to the operating system when an application makes a system call to signal,modify,or wait for another process.
CREDENTIALS:-
Each process must have an associated user ID and one or more group IDs that determine the rights of a process to access system resources and files.
PERSONALITY:-
Process personalities are found under linux systems,each process has an associated personality identifier that can modify slightly the semantics of certain system call.
Creating Processes
Traditionally, resources owned by a parent process are duplicated when a child process is created.
Cost savers:
Copy on write – parent and child share pages that are read; when either writes to a page, a new copy is made for the writing process.
Lightweight processes – parent & child share page tables (user-level address spaces), and open file descriptors.