This document provides an overview of Linux for beginners. It introduces Linux distributions, getting started with the command line interface, files and directories, processes, and basic shell scripting. The document is an agenda for a Linux course aimed at complete beginners to introduce fundamental Linux concepts and commands.

1. Linux for Beginners RAHUL SINGH Rahul projects1991@gmail.com

2. Agenda Introduction Linux Distributions Quick Start Files Process Shell & Programming Networking Security

3. Introduction This course is for beginners What you learn General introduction to GNU/Linux OS Basic operations in Text Mode A little about administration What you don't learn learn In depth Linux structure Kernel Internal System programming …

4. Introduction Security perspectives OS role Govern any things in computer Has privilege Insecure OS insecure machine

5. Introduction Why Linux? Free Open Source, Freedom, GPL (GNU Public License)‏ No charge More secure Open source OS for computer scientists You see what happen, no hidden things You need it

6. History 1960 MULTICS, Multiplex Computing System 1974 in AT&T Free Unix Free BSD POSIX Unix is commercial MINIX Simple and free UNIX liked OS, by Tanenbaum

7. History 1991 Linus Torvalds Free kernel for i386 5 Oct 1991 in newsgroup of minix Linux 0.0.2 1994 Linux 1.0 Linux Logo TUX

8. Now linux-2.6.26, www.kernel.org Multitasking, SMP, multi-user Wide range of CPUs Popular OS in universities and academic research Open source Platform of network services Wide range of network protocols and services Platform for embedded development

9. Linux Distributions What required OS, kernel, kernel-space Applications, user-space Interfaces and basic commands Applications Services Kernel by Linus and world wide developers Most of applications by GNU project GNU : GNU is Not Unix Our operating system: GNU/Linux

10. Linux Distributions Red Hat & Fedora Stable and commercial support SuSE Most updated and user friendly Supported by Novel UBUNTU New fast growing user friendly Debian based Debian Most complete distribution, the Sarge

11. Linux Distributions Bluecat Linux for embedded systems LinuxPPC Linux to run on PowerPC machines Astaro Security applaince, Firewall, Antivirus Live CD KNOPPIX, PHLAK, Karamad, ...

12. Quick Start Access to Linux Remote Local Remote Through network Telnet, insecure and disabled now SSH, Secure Shell Protocol Local Linux installation or Live CDs

13. Quick Start System powered on BIOS POST Bootloader, Grub or LiLo Initialize Hardware Kernel extraction Kernel Initialize Hardware Kernel data structures initialization

14. Quick Start System Services Configured Services network and network services User interface G raphical Called as X window system, it is a service KDE, GNOME Text, Shells Switch between them: ALT-F? and CTRL-ALT-F? Screen 7 is the X

15. Text vs. X Contrary to MS Windows X isn't integrated into OS X is just an application Shell Interactive program, interface between user and kernel Real power of Linux, specially for hackers and administrators Bash (Brown Again Shell), tsh, csh We study Linux Text Mode and just applications not Kernel

16. Bash After successful login, you get shell prompt $ : user # : root There are two privilege in user space reset : reinitialize your screen Linux is case sensitive Autocomplete: commands and file names Commands in $PATH File name in specified path

17. Bash Linux is multiprocess, even in command line Process can be run in background Widecards * : string ?: a char []: regular expression IO redirection to file > : overwrite, 2> : overwrite by stderror >> : append < : Read input

18. Bash IO redirection to a process | : pass output of command as input to other command One of the main features in UNIX-like systems Simple commands which are piped together Some short-cuts CTRL-D: Logout, End of file CTRL-L: Clear Screen CTRL-C: Stop CTRL-Z: Suspend CTRL-E: cut to end of line CTRL-U: cut to start of line

19. Bash History for each user Use arrow keys ! # : # command ! <start_of_command>: last command started with ... CTRL-R: search history history : see command history .bash_history : saved $HISTSIZE number of command

20. Linux/shell vs. Windows/cmd Path separator: / not \ File extensions have NOT any meaning Hidden file started by ., .bashrc, .bash_history End of file is CTRL-D New line is \n not \n\r Options are passed by - or -- All system configurations are saved in text files

21. Help & Doc Command's builtin helps: -h or --help Man pages Info pages Documents in /usr/share/doc Info pages are NOT complete Easy to use info <command name> or pinfo <command name> whatis

22. Help & Doc Man pages Most complete documentation in Linux Very technical Title, description, see also and files man <man-category> file/command/function searched in <MANPATH> manpath : find out the <MANPATH> configuration file: /etc/manpath.conf man -k topic : search topic in titles = apropos man -K topic: search topic in body

23. Mans /usr/share/man man1: User commands man2: System libraries man3: Programming libraries man4: Special files man5: File formats man7: Misc. network protocols, ... man8: System administration Other mans: Application man pages

24. Internet documents The Linux Documentation Project: www.tldp.org Tutorials HOWTOs Software home pages Mailing lists Everything is googlized

25. Files Everything in Linux is file, if it is NOT process Files can be Regular file Directory Links device named pipe, ... Uniform interface, open, read/write, close You should fully understand the Linux file structure

26. Files Files system User Space, a tree structure Kernel Space, VFS and file system depended drivers What file systems in Linux Kernel configuration depended ext2, ext3, jfs, nfs, fat, ntfs, ... man fs mkfs.ext2, mkfs.ext3, mkfs.fat, ... make file systems

27. File system structure /boot Bootloader, bootloader config and kernel images /bin Binary files, basic utilities, required for boot /sbin System binary, system management tools /lib Shared libraries and kernel modules

28. File system structure /etc System configuration, passwords, service config /home Home directory of users /root Home directory of root /var log files, message files, lock files, www root, ...

29. File system structure /tmp temporary files, socket files, pipe files /usr Like the /, /usr/include additional directories bin, sbin, / opt Additional softwares /proc Virtual file system, process and system information Kernel Interface in user space

30. File system structure /dev Device files, block devices, character devices /sys Kernel interface for hardwares info and management /mnt and /media Add new media and file system into your file system New media has its own file system (kernel level driver)‏ mount -t vfat /dev/sdb1 /mnt/flash

31. File System Navigation List directories ls Options: -a -l -h -R Walking in file system Absolute vs. Relative path cd <path> cd , cd –, cd ~ pushd popd

32. File System Navigation & Modification Find where are you, absolute name pwd Make directory mkdir <directory path> Remove empty directory rmdir <directory path>

33. File System Navigation & Modification Remove file rm <file name> rm -r <directory> -i : ask you, -f : force Secure remove shred -n : number, -z : fill zero shred -n 10 -z -v /tmp/xxx

34. File System Navigation & Modification move file and directories mv <source> <destination> copy file and directories cp <source file> <destination file> cp -r <source directory> <destination directory> What is the rename?

35. File System Navigation & Modification Links (like windows short-cuts)‏ Two Types Hard (only for files) and soft (files & directories)‏ Hard ln <target file> <link name> Soft ln -s <target name> <link name> View Links readlink <link name>, ls -l

36. File Commands Commands File as an object File content Alert timestamp of file Creation, access and modification touch <file name> : update mod. time to now -a : access time, -m : modification time -t : set time create new file

37. File Commands Find files and directories find <path> <regular expression> name, size, time, type, permission, ... find /etc/ -name *.conf -exec cp '{}' /home/backup ';' Where are commands and man pages whereis <command name> Which command is executed which <command name>

38. File Commands Archive Create: tar -cf <archive name> <directory> Extract: tar -xf <archive name> File Compression gzip <file name>, gunzip <zipped file name> best compress: -9 bzip2 <file name>, bunzip2 <zipped file> z* commands zcat, zdiff, zless

39. File Security File permissions ls -l -rwxrwxrwx: -(user)(group)(other)‏ In binary format -421421421 r: read, w: write, x: execute

40. File Security More file permissions t: sticky bit. Others can not delete your file even with “w” permission s & g: Set User/Group ID. Change process id to file owner Chang permissions chmod [ugo][+-=][rwx/binary] file Attributes: undelete, fill zero, append only, ... lsattr, chattr

41. File Security Default permission umask: Invert of your permission umask 077 : no one else can do anything Chang owner and group (only root)‏ chgrp <group> file chown <user> file

42. File Commands Most important file type in Linux: Text Config files Log files Source codes File type file <file name> Binary files xpdf, gimp, openoffice2, firefox, konqueror, xdiv, kde, ...

43. File Commands What is in a file cat <file name> tac <file name> View large files more <file name> or pipe: ls -l | more less <file name> or pipe: cat test.txt | less View not all of file tail -# <file name>, -f is continues head -# <file name>

44. File Commands Search content of file grep <regular expression> <file name> -i : ignore case, -v : invert result, -r : recursive Count file words wc <file name> -l : Lines, -w : words, -c : characters Difference between files diff <file 1> <file 2> -Nu : create patch

45. Editors Again Text editor Text Editors X editors text mode editors Again text mode editors X editors gedit, kwrite kate

46. Editors emacs Old and very user friendly Menu based, F10 mcedit A part of the midnight commander Menu based, easy to use vi & vim (vi improved)‏ Difficult Editor for programmers

47. vim Three modes Input mode: edit your document Command mode: simple commands Line input mode: special and advance commands Input mode Go from command mode by i or a Type what you want Arrow keys, del , home , ... are workings

48. vim Command mode, the default mode Go from input mode by: Esc Navigation commands home : start of line end : end of line b : previous word w : next work :# : go to line #

49. vim Edit commands x : cut a char #dw : cut # of words #dd : cut # of lines d$ : cut to end of line, d^ : cut to start of line #yw : copy # of words #yy : copy # of lines p : past u : undo

50. vim Line Input mode Go from command mode by : :w : save file, :w! : force to save :e <filename> : open file :q : quit, :q! : force to quit :! <any command> : run shell command /<str> : search str :#1,#2 s/ <str1> / <str2> /[c,g] : replace

51. Process In Linux, every things is file, if it is NOT a process Linux is multi-user, multi-process, time-sharing OS Each process has a unique id and a parent (tree)‏ Process can be run in Foreground Background Foreground is default

52. Process Background & at end of command suspend (CTRL-Z), send resume signal ( bg <job id>)‏ Process id is NOT job id fg <job id> : Job come from background to foreground jobs : list of jobs

53. Process Scheduling, running in background at time -f <file name>, atq , atrm <id> cron, crontab, man crontab nohup <command> & : Leave job running Priority less nice is better nice -# <command> : priority is decreased by # renice # <process id> : Change process priority

54. Process Monitoring ps : list of your process ps aux : all running process, with command Lines top : top processes ksysgaurd : Graphical monitor, more than process monitor pstree : tree of running processes /proc/process-id : kernel information about processes

55. Process Process and Signal Signals are notifiers Kernel and users can send signals skill - <signal number> <process id>: user send signal skill -L : List of signals man 7 signal : Full description of signals kill <procees-id>, kill -9 <process-id> : Kill the process killall -9 <process name> : kill the process

56. System Information uname -a, -r : Kernel name dmesg : Kernel messages /var/log/ : system logs (syslogd) and application's messages date : date of system uptime : How long time your system is alive? iostat <device name>: usage of cpu and device users, who, w : list of on-line users finger <user-name>/@<computer name>: remote users info

57. Shell Executable applications Binary programs: usually in developed in C Scripts: shell, perl, awk, python, ... Shell (Bash)‏ After login, your shell executes ( /etc/passwd )‏ .bash_profile /etc/bashrc .bashrc

58. Bash Environment Variables Save, parameters and some configurations Some important variables $PATH : Path of commands $HOME : Your home directory $SHELL : Your shell address $PS1 : Bash prompt $USER : Your login name

59. Bash Define a variable ABC=“This is test” View variable content echo $ABC Define variable for subsequent shells export AAA=“This is test” View all variables printenv

60. Bash Script Bash programming language Variables User defined variables Built in variables: $0, $?, ... All commands

61. Bash Script Control statements for <name> in <word>; do <commands>; done case <variable> in x) <command>;; y) <commands>;; esac if <condition>; then <commands>; elif <condition> then <command>; fi while <condition>; do <commands>; done

62. Example vim test.sh #!/bin/bash for file in *; do if grep -q $1 $file; then echo “Found in file: “ $file fi; done; exit 0 chmod +x test.sh ./test.sh test

63. C programming GCC: GNU Compiler Collection C, C++, Java, ADA, Fortran, ... Tools to build C or C++ program cpp : C preprocessor cc : C Compiler c++ : C++ Compiler as : The assembler ld : Linker gdb : GNU debugger

64. C programming All steps altogether gcc -o <output name> <input C> Intermediate results -c : Just compile, with out linking -S: Produce assembly code -E: Just process the file -g: Add debugging options

65. C programming (make & Makefile) Open source world Automate compiling large packages: make & Makefile target : req1 req2 .... Rule1 to make target Rule2 to make target req1 : req11 req12 Rule11 to make req1 ....

66. Installing programs Binary format Distribution depended Red Hat & Fedora: rpm & yum Debian based (Ubuntu): apt-get Source code ./configure make make install

67. Networking Most of network protocols are implemented in Linux Application layer: bind, apache, sendmail, ssh, ftp, NFS Transport layer: TCP, UDP Network Layer: IP, IPX, ATM Physical layer: PPP, Ethernet, 802.11 Configurations On line Config files

68. Networking Network interface (Ethernet)‏ ifconfig eth0 10.10.10.1 netmask 255.255.255.0 up Red Hat: /etc/sysconfig/network & networking Ubuntu: /etc/network/interfaces Routing route add -net 192.168.0.0/24 gw 10.10.10.2 dev eth0 /etc/sysconfig/networking & network

69. Networking DNS /etc/resolve.conf /etc/hosts Host Name hostname /etc/hostname IP suit: ip route, ip address, ip route ....

70. Networking Monitoring and Troubleshooting List of all connections: netstat -an Find route and its MTU: tracepath, traceroute Check liveness: ping Your machine ip traffic: iptraf Sniffer: tcpdum, ethereal Scanners: nmap, amap, ...

71. Using from Network Remote shell: telnet, ssh Remote file transfer: ftp, lftp, sftp, scp Web: lynx, firefox Download: wget, crul, prozilla Mail: fetchmail, mail DNS resolver: nslookup, dig Windows NetBIOS: smb* commands

72. Services Linux services Network services: web, mail, ... Local services: udev, alsa Startup scripts /etc/init.d/<sevice name>, /etc/init.d/apache2 Configuration files /etc, /etc/apache2

73. Security Security Local: File security, Process security Network SELinux: role-based access control and sandboxing Each user Has its own unique ID, /etc/passwd Belong to some groups, /etc/group

74. Security Process security Each process has its own user id You can kill only your processes, root can do anythings

75. Network Security Statefull Firewall: iptables IDS: snort VPNs IPSec: openswan SSL: stunnel, openswan Secure services SSH, SSL, Tunneling

76. Now is the end time of my presentation But it is the start of your Linux learning