overview of linux kernel
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Overview of Linux Kernel
Linux is a type of UNIX
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Free Software and Open Source
Linux Most successful for Open sourcesoftware
Open source software source code isfreely available such that anyone canmodify, read and redistribute
Open source licensed under GNU General
Public License(GPL) version 2(Closed source software distributed only in
binary form)
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Linux Distributions
Linux Distribution = Linux Kernel + tools +
Window Managers + Applications
System programs of Linux are developedby Free Software Foundation (FSF) GNU
project.
Organizes the tools and applications into
groups of header and executable files.
Grouping packages used for compilation
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Linux Distributions are:
DebianBetter package mgmt system
Initial installation is difficult
Red Hat/Fedora
Red hat Enterprise-Bussiness,Govt and Industry,stable,in America
Fedora Core- For Individual Users,less stable
Mandriva
Easier to install and system configuration,setup
SUSE
business,govt,industry and individual users
Its installation and administration tool Yast2,in Europe Gentoo
New Linux Distribution,all the packages are compiled for specificconfiguration of machine
Yellow Dog
PPC based Linux Distribution(Power PC processor based)
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Linux Operating System
Kernel Space+User Space
Kernel is all hardware resources
Outermost layer of procedures- Kernel
Hardware management functionalities-Kernelspace
User associates with OS by User space
User space does not access the Kernel directly
but by system calls Within the Kernel, system call procedures call onto other procedures not in user space for finerfunctionality
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Linux Operating System
The subset of procedures not visible to user
space is made up in part by functions from
individual device drivers
Device Drivers - well defined interface fns for-system call and kernel
Figure: LINUX ARCHITECTURE
Application Application Application
Application
System calls
Device driver Device driver Device driver Device driver
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Overview of Linux Kernel
Kernel Organization-Linux supports numerousarchitectures
runs on many types of processors
Like alpha,arm,i386,ia64,ppc,ppc64 etc Linux source code supports all abovearchitectures
Most source code - C, assembly language andhardware independent
Machine dependent portion - boot strapping,exception vector handling ,address translation,device I/O-system calls
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Kernel Interface
Various components (subsystems) of Kernel are
File system
Processes Scheduler
Device drivers
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User Interface
Users communicate with system-Programs
User logs in-thru a terminal or a virtual terminal
In Linux a program is called Mingetty forVirtual terminaloragetty forserial terminals monitors the inactiveterminal waiting for notify who is logged on
To Log in EnterAccount name and password
called login the system
Getty program -all account names and password
authentication allows them to system if there is a match or terminates if
no match are all respawned if once terminated
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User Interface
Login successfully- User program executes aShell
A shell is a command Interpreterand consists ofa listening process
Listening Process interprets and executes therequests typed
Shell displays a Command Prompt
User interacts with the system thru syntaxdefined by shell
Programs a user can call- Exe files
Execution of requests-shell spawning
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User Identification
User Id-UID to validate users permission
with respect to file accesses
User log in to home directory User is a member of one or more group
which has a group-id(GID)
A file is associated with UID or GID
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Files and File System
File system provides a method for storage andorganization of data
Linux supports file concept as a device independentsequence of bytes
User can access a file regardless of device like harddisk,cd,floppy etc
Files are grouped in-directories
File structure is a hierachical tree- called file hierarchy
Top most node in which all files and directories arestored- root(identified by /)
File system is in hard disc partition
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Directories Files and Path names
Every file in a tree has path name indicates
name and location
A file has directory in which it belongs called
current working directory or directory user islocated in is called relative pathname
A path name taken from root of the system-
Absolute path name
Eg:/home/rose/src/file.c-Absolute path name
Eg:src/file.c-relative path name
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Hierarchical file Structure
/
Bin Boot
anna rose sophi
src
file.c
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