Information Technology College of HoChiMinh city Faculty of Information Technology Course: Fundamentals of Linux OS Unit Linux Introduction Lecturer: Võ Tấn Dũng votandung@yahoo.com http://sites.google.com/site/votandungsg/ Before Linux • In 80’s, Microsoft’s DOS was the dominated OS for PC • Apple MAC was better, but expensive • UNIX was much better, but much, much more expensive Only for minicomputer for commercial applications • People was looking for a UNIX based system, which is cheaper and can run on PC • Both DOS, MAC and UNIX were proprietary, i.e., the source code of their kernel is protected • No modification is possible without paying high license fees VÕ TẤN DŨNG What is Unix? • A multi-task and multi-user Operating System • Developed in 1969 at AT&T’s Bell Labs by – Ken Thompson (Unix) – Dennis Ritchie (C) – Douglas Mcllroy (Pipes) • Some other variants: System V, Solaris, SCO Unix, SunOS, 4.4BSD, FreeBSD, NetBSD, OpenBSD, BSDI,… VÕ TẤN DŨNG Beginning of Linux – – – A famous professor Andrew Tanenbaum developed Minix, a simplified version of UNIX that runs on PC Minix is for class teaching only No intention for commercial use In Sept 1991, Linus Torvalds, a second year student of Computer Science at the University of Helsinki, developed the preliminary kernel of Linux, known as Linux version 0.0.1 VÕ TẤN DŨNG After that… –Soon more than a hundred people joined the Linux camp Then thousands Then hundreds of thousands –It was licensed under GNU General Public License, thus ensuring that the source codes will be free for all to copy, study and to change –Linux has been used for many computing platforms: PC, PDA, Supercomputer,… –Not only character user interface but graphical user interface is available –Commercial vendors moved in Linux itself to provide freely distributed code They make their money by compiling up various software and gathering them in a distributable format VÕ TẤN DŨNG Linux Today • Many Linux Distributions – Slackware (one of the oldest, simple and stable distro.) – Redhat • RHEL (commercially support) • Fedora (free) – – – – – – – CentOS (free RHEL, based in England) SuSe ( based in German) Gentoo (Source code based) Debian (one of the few called GNU/Linux) Ubuntu (based in South Africa) Knoppix (first LiveCD distro.) And now, ANDROID of Google VÕ TẤN DŨNG Variety of Linux Shell      Shell interprets the command and request service from kernel Similar to DOS but DOS has only one set of interface while Linux can select different shell – Bourne shell (bash) – Korn shell – C shell Different shell has similar but different functionality Bash is the default for Linux Graphical user interface of Linux is in fact an application program work on the shell VÕ TẤN DŨNG The File System – – Linux supports many file-systems: ext, ext2, ext3, xia, minix, umsdos, msdos, vfat, proc, smb, ncp, iso9660, sysv, hpfs, affs,… Common Linux Subdirectories: VÕ TẤN DŨNG Some important directories – – – – – – – – – – – The starting point (/) is called the root directory /usr: contains executable commands, system administration utilities, and library routines /etc: contains system configuration files /home: contains the user‘s home directory /dev: contains files which are pointers to device names /root : the root user's home directory /bin : important Linux commands available to the average user /boot : the files necessary for the system to boot /lib : contains system libraries /mnt : contains mount points When you temporarily load the contents of a CD-ROM, USB drive or a HDD partition, you typically use a special name under /mnt /sbin : contains essential commands that are only for the system administrator VÕ TẤN DŨNG Log in your Linux system – – – – – – You must have a user account on the system to log in The user account is defined in the /etc/passwd file The “root” account is the system administration account File /etc/passwd : each entry in this file is made up of seven fields separated by a colon Placeholder, that is /etc/shadow file, it maintains the field for the password The /etc/shadow file contains encrypted passwords These two files can only be read by the system administrator Example: #cat /etc/passwd OR #cat /etc/shadow VÕ TẤN DŨNG Log in, log out • Start up your computer, then type in your username and password: – login: (type in your username here) – password: (type in your password here) • If you want to log out your Linux current session, using exit command or key-combination : – exit – VÕ TẤN DŨNG Changing User Password • Using passwd command for changing the user password $ passwd Changing password for cis1 Old password: New password: Retype new password: Hashed database not in use, only /etc/passwd text file updated $ VÕ TẤN DŨNG Test who are logging in • whoami, tells you who is currently logging in to a terminal $ whoami user1 $ • To see more details about the user who is currently loging in to a terminal, type the command “who am i” as follows $ who am i user1 pts/4 $ Mar 08:40 (172.18.10.22) VÕ TẤN DŨNG Current log-in users • The who command, will tell you who are log-in right now $ who jlp tty0 sep 20 10:05 you tty2 sep 22 10:34 host name If #, that means user root If $, that means regular user (not user root) [root@redhat9 tmpdocs]# current user current working directory VÕ TẤN DŨNG Viewing hostname • hostname command displays the name of the host computer you have logged into $hostname redhat9 $ • To change the host name: $hostname VÕ TẤN DŨNG Shutdown your Linux system – Some CLI commands to shutdown your Linux: halt, poweroff, reboot, shutdown, init Examples: #shutdown -r “It will be rebooted in minutes!” #shutdown -h “Your system will be turned off in minutes“ #shutdown -r now #reboot #init #halt #poweroff VÕ TẤN DŨNG Using runlevel – – – A runlevel is a mode of operation of the Linux OS, that provides a particular set of services File : /etc/inittab Using init command to switch between levels VÕ TẤN DŨNG Displaying Man Pages • Use the man command to display on-line man pages for commands Command Format man Example: $ man cd Reformatting page Wait done CD(1) Linux User’s Manual CD(1) NAME cd, chdir, pushd, popd, dirs - change working directory SYNOPSIS /usr/bin/cd [ directory ] sh cd [ argument ] … … SEE ALSO csh(1), ksh(1), pwd(1), sh(1), chdir(2), attributes(5), environ(5) (END) VÕ TẤN DŨNG Scrolling in Man Pages – Use the following keys to control the scrolling capabilities while using the man command: VÕ TẤN DŨNG Command-Line Syntax At the shell prompt, you can type commands Commands are instructions which tell the system to perform an action The general format for Linux commands is: #command [option (s)] [argument[s]] VÕ TẤN DŨNG Command-Line Syntax (cont.) Examples: ls -a -l /etc/mydir useradd -u 503 -g sales alan mkdir -p /mnt/ docs/xls/priv cp -i sales.doc /mydoc cat /mnt/ploppydisk/baitap.txt head -6 /usr/dict/words tar -xvf /home/backup.tar VÕ TẤN DŨNG Some Linux’s commands mkdir – make directories ls – list directory contents cd – changes directories pwd print name of current working directory cp – copy files and directories mv – move (rename) files rm remove files or directories find – search for files in a directory hierarchy history – prints recently used commands cat – concatenate files and print on the standard output echo – display a line of text wc print the number of newlines, words, and bytes in files sort – sort lines of text files su – change user ID or become superuser zip – package and compress (archive) files fdisk – partition manipulator VÕ TẤN DŨNG Control Characters Control characters are used to perform specific tasks such as stopping and starting screen output When displayed on the screen, the Control key is represented by the caret symbol (^) To enter a sequence of control characters, hold down the Control key and press the appropriate character on the keyboard VÕ TẤN DŨNG END OF UNIT • remember to your homework (see http://sites.google.com/site/votandungsg/) VÕ TẤN DŨNG ... for Linux commands is: #command [option (s)] [argument[s]] VÕ TẤN DŨNG Command-Line Syntax (cont.) Examples: ls -a -l /etc/mydir useradd -u 503 -g sales alan mkdir -p /mnt/ docs/xls/priv cp -i... Using init command to switch between levels VÕ TẤN DŨNG Displaying Man Pages • Use the man command to display on-line man pages for commands Command Format man Example: $ man... your password here) • If you want to log out your Linux current session, using exit command or key-combination : – exit – VÕ TẤN DŨNG Changing User Password • Using passwd command