Linux Operating system By Quontra Solutions

Information about Linux Operating system By Quontra Solutions

Published on August 25, 2014

Author: quontra123



Linux OS Concepts Presented By QuontraSolutions Linux Online Training-Attend Free Demo. Email:[email protected] Call Us: +1 404-900-9988 Web: : Linux OS Concepts Presented By QuontraSolutions Linux Online Training-Attend Free Demo. Email:[email protected] Call Us: +1 404-900-9988 Web: Operating System: Operating System A program or a software that governs the functioning of other programs Interface between User and the Hardware Allocates resources for tasks Allocates tasks to programs Manages space and time Controls the devices Types of Operating System: Types of Operating System Tasks Uni tasking Multi tasking Users Single User Multi User Processing Uni processing Multi processing Timesharing FOSS: FOSS Free Open Source Software Free – Means Liberty and not related to Price or cost Open – Source code is available and any body can contribute to the development. Organization independent Kernel: Kernel Core or nucleus of an operating system Interacts with the hardware First program to get loaded when the system starts and runs till the session gets terminated Different from BIOS which is hardware dependent. Kernel is software dependent Kernel types: Kernel types Monolithic All OS related code are stuffed in a single module Available as a single file Advantage : Faster functioning Micro OS components are isolated and run in their own address space Device drivers, programs and system services run outside kernel memory space Supports modularity Lesser in size Shell: Shell Program that interacts with kernel Bridge between kernel and the user Command interpreter User can type command and the command is conveyed to the kernel and it will be executed Types of Shell: Types of Shell Sh – simple shell BASH – Bourne Again Shell KSH – Korne Shell CSH – C Shell SSH – Secure Shell To use a particular shell type the shell name at the command prompt. Eg $csh – will switch the current shell to c shell To view the available shells in the system, type cat /etc/shells at the command prompt To view the current shell that is being used, type echo $SHELL at the command prompt 4 Freedoms with FOSS: 4 Freedoms with FOSS Freedom to run the software anywhere Freedom to study how the programs work. i.e source code will be accessible Freedom to redistribute copies Freedom to improve the software If a software has all these 4 freedoms, then it is a FOSS Copyleft: Copyleft Termed by Richard Mathew Stallman Liberates information from the proprietary legal encumbrances associated with conventional copyright Copyleft statement: “Verbatim copying and redistribution are permitted in any medium provided this notice is preserved.” History: History Multics – 1964 Unics – 1969 Minix – 1990 Linux – 1991 Multics: Multics Multiplexed Information and Computing Service Written in 1964 Timesharing OS Last version was shut down on October 30, 2008 Monolithic kernel Unics: Unics Uniplexed Information and Computing System Later renamed as UNIX Written in 1969 Ken Thompson, Dennis Ritchie were among the developers Multi user, Multi tasking and timesharing Monolithic kernel Minix: Minix Minimal Unix Tanenbaum developed this OS Mainly for educational purpose Unix like OS, implemented with Micro kernel. So the name Minix Linux: Linux Developed in 1991 by Linus Torvalds Used in most of the computers, ranging from super computers to embedded system Multi user Multi tasking Time sharing Monolithic kernel Free Software Foundation: Free Software Foundation Founded by Richard Stallman in 1983 Organisation that started developing copylefted programs Project – GNU Project GNU Not Unix Recursive expansion Operating System: Operating System User 1 User 2 Linux OS: Linux OS Linux Distributions: Linux Distributions Redhat Fedora Debian Novell’s SUSE Linux Ubuntu Mandrake Live CDs – Knoppix and more GNU/Linux: GNU/Linux Only the kernel is called by the name Linux The rest are the tools developed under GNU Project Hence the name GNU/Linux Text editors: Text editors Vi Emacs gEdit kWrite TextPad And more… Browsers: Browsers Mozilla First Open source browser Released from Netscape group Firefox High performance, feature rich, standards based web browser Sea Monkey Integrated web application suite derived from the mozilla source code File Management Commands: File Management Commands mkdir - creating directory mkdir dirname rmdir – removing directory and its contents rmdir dirname cd – Change directory cd dirpath cp – Copying files cp file1 file2 mv – Moving or renaming files mv oldfile newfile File Management – contd..: File Management – contd.. ln – Creating links between files ln file1 file2 Difference between copying files and linking files cp src dst Contents of src will be present in dst Changing content in src will not affect contents of dst and vice versa ln src dst Contents of src will be present in dst Changing content in src or dst will get reflected in the other file Commands: Commands Help about commands man, pinfo, info (man <<cmd name>>) Viewing file’s content cat <<filename>> Viewing users, processes who – List all Users who am I – List the current user pstree – displays all processes running in the system in tree format ps – displays processes owned by the current user Changing file permission/owner chmod – changes file permission chown – changes file owner Listing files and Emulating Terminal: Listing files and Emulating Terminal Listing files in a directory ls – Lists all files in a directory ls –a – Lists all files (including hidden files) ls –l – Lists files in a directory along with owner information, permission etc Terminal Emulator xterm – Generates a terminal xterm –fg color –bg color –rightbar : Generates a terminal with the specified background and foreground color and a scroll bar on the right side VI Editor: VI Editor Popular text editor Just type vi <<filename>> at the prompt and hit the enter key. A new file will be opened Type the contents needed and save To save, press the Esc Key and then press : (colon) w q and then enter To quit with out saving Esc + : + q and then enter Vi editor: Vi editor Navigation Left - h Down - j Up - k Right - l Top of the screen – H (shift + h) //caps lock will not work Middle of the screen – M (shift + m) Bottom of the screen – L (shift + l) $ - End Key, 0 – Home Key Edit Commands Cut – X, x Copy – yy, yw Paste – P, p Pattern matching: Pattern matching grep – GNU Regular Expression Processor Finds the words / patterns matching with the search and displays the line containing the patterns. Search is limited to a file Redirection and Pipes: Redirection and Pipes Redirection Input redirection wc < file1 – Content of file 1 is given as input for wc command that counts the no of lines, words and characters in a file Output redirection cat file > newfile – Copies file’s content to newfile. Over writes the existing content cat file >> newfile – Appends the new content to the existing content Pipes Output of first command is input for the second and so on who | wc –l – Number of lines in the output of who command will be displayed C Program in Linux: C Program in Linux Open a file with extension .c from the command prompt using vi editor vi hello.c Type the contents and save (Esc : wq!) Compile the file gcc hello.c Run the executable ./a.out Compile file with output option gcc –o hello hello.c Run the executable ./hello Shell Scripting: Shell Scripting Shell scripting is the most useful and powerful feature in Linux Minimizes typing of repetitive command Can schedule jobs to run in the system Can initiate back up activities for system administration Similar to batch files in DOS, but more powerful than Batch files Working with shell script: Working with shell script Open a file with extension .sh using vi editor We can type any number of commands that we use to type at command prompt Save the file Execute the file sh ./ (if the file has execution permission) Shell Scripts: Shell Scripts To Print a line echo “Hello World” (Prints Hello World in the screen) To read a line read n (Stores the content entered by user in variable n To Comment a line # This is a comment Only single line comment is available. For multi line comment, we need to use # symbol in lines which we want to comment. Loops: Loops For loop for i in 1 2 3 4 5 //Loops 5 times do Body of the loop done for (( i=0; i<5; i++ )) do Body of the loop done While Loop: While Loop while [ condn ] do body of the loop done We need to ensure that the while loop condition is terminated in a finite way Conditions: Conditions We can have if, if else, if elif else and case statements (Nested if statements are also possible 1. if [ condn ] then fi 2. if [ condn ] then else fi 3. if [ condn ] then elif [ condn ] then else fi Conditions (Case): Conditions (Case) case expr in Option1) stmt ;; Option2) stmt ;; *) stmt ;; esac Every option should be terminated with a double semicolon. Denotes default case Case should be termniated with esac Comparison: Comparison For integer comparison we have the following -eq : equal to -ne : not equal to -lt : less than -gt : greater than -le : less than or equal to -ge : greater than or equal to Comparison: Comparison For string comparison we have = : equal to ~= : not equal to For logical operators -a : AND -o : OR Arrays: Arrays Initialising an array A[0] = 10 A[1] = Hi Using an array ${A[0]} : retrieves 10 Here arrays can contain data belonging to different data types Uninitialised index in arrays will have null value by default Functions: Functions Local Function Written at the command prompt Lasts for the current session alone Global Function Written in .bashrc file Available as long as the definition is there in .bashrc file Function in shell script Available with in the file alone Parameters: Parameters Sample function Functionname() { echo $1 } Calling function: Functionname Ram Result: Ram Environment variables: Environment variables We can view the environment variables through set or env command The set command will display all the global functions written by the user The env command displays only the variables and not the functions We can reassign values for the variables either temporarily or permanently Temporary Type varname=value at the command prompt Permanent Type varname=value in .bashrc at the root directory Aliasing: Aliasing Alias – Alternate name for an entity Entity here refers to command We can give another name or alias name for a command either at the command prompt or in the .bashrc file. The former will be temporary and will vanish if the session ends and the latter will be permanent as long as the definition exists in the .bashrc file Alias and Unalias: Alias and Unalias alias newname=oldname Eg alias copy=cp Then we can use copy in the same way we use cp command Eg copy file1 file2 //copies content of file1 to file2 To remove alias use unalias command unalias copy After this we cannot use copy to perform copying function

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