Introduction to Linux - Boston University

Introduction to Linux - Boston University

Introduction to Linux Linux at the Command Line Don Johnson of BU IS&T About the class Well start with a sign in sheet that include questions about your Linux experience and goals. Well end with a class evaluation. Well cover as much as we can in the time allowed; if we dont cover everything, youll pick it up as you continue working with Linux.

This is a hands-on, lab class; ask questions at any time. Commands for you to type are in BOLD What is Linux? The Most Common O/S Used By BU Researchers When Working on a Server or

Computer Cluster What is Linux? Linux is a Unix clone begun in 1991 and written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. 64% of the worlds servers run some variant of Unix or Linux. The Android phone and the Kindle run Linux. What is Linux?

Linux + GNU Utilities = Free Unix a set of small programs written by Richard Stallman and others. They are the GNU utilities. Linux is an O/S core

written by Linus Torvalds and others AND What is Linux? Small programs that do one thing well (see unix-reference.pdf)

Network: ssh, scp Shells: BASH, TCSH, clear, history, chsh, echo, set, setenv, xargs System Information: w, whoami, man, info, which, free, echo, date, cal, df, free

Command Information: man, info Symbols: |, >, >>, <, ;, ~, ., .. Filters: grep, egrep, more, less, head, tail Hotkeys: , File System: ls, mkdir, cd, pwd, mv, touch, file, find, diff, cmp, du, chmod, find File Editors: gedit, nedit Connecting to a Linux Host Windows Client Software You need a xterm emulation

software that emulates an X terminal and that connects using the SSH Secure Shell protocol. Windows Use StarNet X-Win32: ed-software/xwindows/xwin32/ Connecting to a Linux Host Mac OS X Client Software Mac OS X Terminal is already installed Why? Darwin, the system on which Apple's Mac OS

X is built, is a derivative of 4.4BSD-Lite2 and FreeBSD. In other words, the Mac is a Unix system! Let the Linux Lab Begin! Your Instructor Today The Ideal Lab Facility Connecting to a Linux Host Windows Client X-Win32/X-Config

Wizard Name: katana Type: ssh Host: (Off-campus, must include domain ) Login: Password: Command: Linux Click katana then Launch Accept the host server public key (first time only) Connecting to a Linux Host Mac OS X Client

Terminal Type ssh X or ssh Y (less secure) Obtaining the Course Material

From the lab computer Using File Explorer, copy the directory \\\SCV\Training\Introduction to Linux to My Documents on your lab machine Linux Connect to using X-Win32 and run this command: cp -Rv /project/ssrcsupp/linux_class ~/ From a browser, download: The Shell

A shell is a computer program that interprets the commands you type and sends them to the operating system. Secondly, it provide a programming environment consisting of environment variables. Most BU systems, including the BU Linux Cluster, support at least two shells: TCSH and BASH. The default shell for your account is TCSH. The most popular and powerful Linux shell today is BASH. To determine your shell type:

echo $SHELL (shell prints contents of env echo $SHELL (shell still processes env. variable) echo $SHELL (shell treats env. variable as simple literal) The complete environment can be printed with set, setenv (TCSH) and set (BASH). To determine the path to the shell program, type: which bash which tcsh

Change the shell with chsh /bin/bash (provide path to new shell as a parameter, meaning to be explained soon) The Shell Output of the echo, which and chsh commands System Information After you connect, type

shazam whoami hostname date cal free Commands have three parts; command, options and parameters. Example: cal j 3 1999. cal is the command, -j is an option (or

switch), 3 and 1999 are parameters. Options have long and short forms. Example: date u data --universal What is the nature of the prompt? What was the systems response to the command? System Information Output of the whoami, hostname, date, cal and free Command History and Simple Command Line Editing

Try the history command Try (only works in BASH shell) Choose from the command history by using the up and down arrows What do the left and right arrow do on the command line? Try the and keys Help with Commands Type

hostname -help man hostname info hostname (gives the same or most information, but must be paged) And Yes, you can always Google it Connect Commands Together with the Pipe Symbol | and Using Filters

The pipe | feeds the OUTPUT of one command into the INPUT of another command. Our first example will use the pipe symbol to filter the output of a command. Try: w w | grep root ps -e -o ruser,comm | grep 'tut The ps command is using both options (dash) and parameters Try both man grep and info grep. See the difference?

The Linux File System The structure resembles an upside down tree Directories are collections of files and other directories. Every directory has a parent except for the root directory. Many directories have children directories. Unlike Windows, with multiple drives and multiple file systems, a *Nix system only has ONE file system.

The Linux File System A Typical Linux File System Examining the File System Try tree L 3 d / | less tree L 3 / | less file /bin/alsac then press cd ~; pwd (This is your home directory where application settings are kept and where you have

write privileges) ls mkdir myPics;mkdir myPics/work;mkdir myPics/friends;mkdir myPics/friends/BU; mkdir myPics/friends/MIT tree myPics Examining the File System Output from the tree, file, pwd and ls commands Demonstration of using the mkdir command Navigating the File System

There are two types of pathnames Absolute (Abs) the full path to a directory or file; begins with the root symbol / Relative (Rel) a partial path that is relative to the current working directory Examples Abs cd /usr/local/lib echo $HOME (one of may environment variables maintained by the shell)

Abs cd `echo $HOME` pwd Rel cd .. Rel cd .. Abs cd /lib (location OS shared libraries) ls d */ (a listing of only the directories in /lib) Navigating the File System Moving around the file system using the cd command Modifying the Linux File System

More useful commands cd (also takes you to your home directory like cd ~) mkdir test echo Hello everyone > test/myfile.txt echo Goodbye all >> test/myfile.txt less test/myfile.txt mkdir test/subdir1/subdir2 (FAILS) mkdir -p test/subdir1/subdir2 (Succeeds) mv test/myfile.txt test/subdir1/subdir2 rmdir test (FAILS) rm Rv test (Succeeds)

Modifying the Linux File System Demonstration of the mkdir, less, mv, rmdir and rm commands The List Command Useful options for the ls command: ls -a List all file including hidden file beginning with a period . ls -ld * List details about a directory and not its contents ls -F Put an indicator character at the end of each

name ls l Simple long listing ls lh Give human readable file sizes ls lS Sort files by file size ls lt Sort files by modification time File Editors Emacs Vim Nedit Gedit

Emacs and Vim are powerful editors used by most programmers. Nedit and Gedit and easy to learn editors useful for new users on a Linux system. Finis

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