Generically, opensource refers to a program in which the source code is available to the general public for use and/or modification from its original design free of charge, in which programmers improve upon the code and share the changes within the community.
some of the open source softwares: Linux, java, php, MySQl, Open Office, Apache Tomcat, Mozilla, Python, Eclipse, etc...
Here we are going to see one of the most popular open source software called Linux.
Introduction to Linux:
Linux:
- Unix-like operating system.
- open source development
- Basically it is a server based operating system
- free software
- Anyone to use, modify, and redistribute software freely.
Some of the Linux distributions:
Red Hat Enterprise, SUSE, Fedora, CentOS, Debian, Gentoo, Knoppix, Mandriva, MEPIS, Slackware, Ubuntu,
- First version of UNIX created in Bell Labs – 1969
- Created by Ken Thompson and Dennish Ritchie.
- Linus Trovalds a Finnish college student Created Linux Kernel in 1991
Some of the Unix-like operating systems:
A/UNIX, AIX, BSD, FreeBSD, GNU, HP-UNIX, IRIX, Linux,
Mac OS, X Minix, NetBSD, NEXTSTEP, OpenBSD, Plan 9, QNX ,
SCO, OpenServer, Solaris, System, V Tru64, Xenix,
History:
- In 1983, Richard Stallman founded the GNU Project, with the goal of developing a complete Unix-like operating system composed entirely of free software. By the beginning of the 1990s, GNU had produced or collected most of the necessary components of this system—libraries, compilers, text editors, a Unix-like shell—except for the core component kernel.
- Meanwhile, in 1991, another kernel was begun as a hobby by Finnish university student Linus Torvalds
- Torvalds originally used Minix on his own computer, a simplified Unix-like system written by Andrew Tanenbaum for teaching operating system design. However, Tanenbaum did not permit others to extend his operating system, leading Torvalds to create a replacement for Minix.
Features of Linux:
- Reliability,
- Multi-tasking,
- Multi user,
- Network application capabilities,
- Most of the scientific software runs on UNIX/LINUX,
- Unix/LINUX is rich in commands and software,
- Development capabilities,
- Graphical user interface,
- Hardware support,
- comes with a built set of compilers/debug tools,
- More secure,
- Virtual console (multiple non GUI logins ie. 6),
- Multiple Desktop (shared workspace),
- Both text mode and GUI logins,
- Everything is a file (including hardware),
- Shell scripts,
- Small single purpose programs,
- Free browsers, office packages,
- Command line help,
- Easy installation,
- In built driver programs.
Is LINUX really UNIX?
Well, yes and no:Yes, because it has essentially the same look and feel like any UNIX operating System.and it offers the ability to run nearly any program that runs on UNIX systems (through API conventions such as POSIX, etc..). No, because the heart of the system (kernel) has a lot of new features that go beyond the classical design philosophy of UNIX kernels.
FILE SYSTEM:
- It is a method for storing and organizing computer files and the data.
- It is used to make it easy to find and access the files.
Some of the file Systems are:
- Windows – FAT32,NTFS,
- Linux – EXT 2, EXT 3.
- CDROM – ISO 9660
File Structure and Directory Structure:
" / "
it is the main or root directory (can access by administrator privilege user)
sub directories of " / "
Root, Home, Bin, Sbin, dev, etc, mnt, tmp, opt, usr, var, lib, boot,
Each subdirectories have some special purpose
root: Super User Directory
home: Contains user Information's
Bin: Binary Executable file (ie.User Commands)
sbin: Binary Executable file (Super User Commands)
dev: Device Files which contains driver files
etc: System Configuration Files (Host name, IP Address, Gateways.
mnt: mount information like CD ROM, Floppy, etc
tmp: Temporary File
opt: Optional Third Party Packages
usr: User, Contains documents of services like DNS, web service
var: Contains LOG information (Time of logged in & out)
lib: Library Files
boot: Booting & Boot Loader Information's
Architecture of Linux OS:
What is Kernel?
The kernel is the central part in most computer operating systems which manages the system's resources and the communication between hardware and software components. It performs various operations like.
1. Process management
2. Memory management (Allocate and delete memory for process),
3. Device management (control the Hardwares),
4. System calls:
It is a well defined programs to instruct the kernel to do various operations and exchange the
data between the kernel and the program.
Shell:
Shell is the interface between user and the kernel. It’s like command prompt.
Types of shells:
- Bourne shell
- BASH Shell (Bourne Again Shell)
- C shell
- K shell
LOGIN:
- Text mode (CUI) login at virtual console (CTRL + ALT +F [ 1 - 6 ])
- Graphical login (GUI) at CTRL + ALT + 7
login: root (for administrator login)
password: (should be minimum 6 letters)
File Permissions:
Linux File security:
every file and directory has permissions set, that determine who can access it
permissions are set for:
- the owner of file (i.e.. current user)
- the group members
- all others
permissions that are set are called read, write, execute permissions.
To set the file permissions chmod command is used.
file permissions may be viewed using ls
$ ls –l filename
file type and file access permissions are symbolized by a 1, 0 character string.
click to see Large imageLinux Basic Commands: 
Click here to see/download Basic Commands
If u have any doubts in the linux, open source, mail me to:
techsun10@gmail.com
