Introduction to Linux (I)

1
Introduction to Linux (I)
CS1103 ????????

• Prof. Chung-Ta King
• Department of Computer Science
• National Tsing Hua University

(Contents from ??? (http//yenjinc.info), Dr.
Sven Hessler, Prof. Cédric Notredame)
2
Outline

• Overview of Unix System
• Basic Commands
• Relative and Absolute Path
• Redirect, Append and Pipe
• Permission
• Process Management
• Install Software
• Text Editor
• Foreground and Background Jobs

3
What Is Linux?

• Linux ????????????????
• ???? (open source)??????? Linux-?????????????????
  
• Linux???
• UNIX1970???Bell Lab????,?????????minicomputers?wo
  rkstations?
• ???? UNIX???????????,????????
• Andrew Tanenbaum??OS???,?? UNIX????????PC??????Min
  ix (1986)
• 1991?Linus Torvalds???Minix??Linux
• GNU??Linux kernel????????

4
Linux Distributions

• ??Linux???? SuSe, Gentoo, Fedora, Debian,
  Ubuntu,
• ????Linux kernel,?????????GNU ??????????? (Open
  Source Software)
• ???????????????????

Linux Distribution ?????
??????????????????,??????????????,?????????
Applications/Open Source Software
????/??????
Linux Kernel
5
Why Linux?

• Used in many servers and embedded systems
• Web servers, mail servers, firewalls, printer
  servers, wifi access points, disk servers
• Google phone (Android), OpenMoko
• Note Many do not have GUI, but text mode
  interface
• Penetrating into desktops and notebooks with
  easy-to-use GUI eeePC, OS X

6
Installing Linux

• Traditional way installing Linux from CD ROM on
  hard disk partitions
• Use virtualization software VMware, QEMU,
  virtual box, XEN
• x86 virtualization the method by which x86-based
  "guest" OS are run under another "host" x86 OS,
  with little or no modification of the guest OS
  (wiki)
• For example on Windows
• ubuntu (http//www.ubuntu-tw.org)
  ubuntu-8.10-desktop-i386.iso
• virtual box (http//www.virtualbox.org)

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Linux????

• Linux??????????????

???????????????????????????????X-window
??,??????????????
Applications
X-window Apps
Server Apps
??????????????
OS Utilities/Applications
Kernel
???????
Hardware
????
8
Linux from Users Perspective

• Underneath the windows GUI system, users interact
  with Linux kernel through shell
• Shell interprets users input as commands and
  pass them to kernel
• Operates in a simple loop
• accepts a command
• interprets the command
• executes the command
• displays a prompt, to notify userthat it is
  ready to accept the next command
• ???????

9
Directory Structure

• Linux???/ (root)?????,????????????/ ??
• ????????? (partition),???/ ??,??mount
  (??)???,??????
• Windows???C\, D\???????
• All directories are in a hierarchical structure
  (tree structure)
• Users have the own directory (home directory)
• The path is the location of a file or directory
  within the tree, e.g. /usr/sbin/bzip2,
  ../../john, /home/john
• Support access control by defining permissions
  for read, write, and execution

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Directory Structure
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Important Directories

• /bin contains files that are essential for
  correct operation of the system
• available for use by all users
• /home stores user home directories
• /var stores files which change frequently, and
  must be available to be written to
• /etc contains various system configuration files
  
• /dev contains various devices as files, e.g.
  hard disk, CD-ROM drive, etc.
• /tmp temporary files

12
Other Things to Know

• Normal user and super user
• There is one special user for administrator,
  which can do anything and is called root or
  superuser
• Case sensitivity
• Linux is case-sensitive
• Multi-user and multi-process
• Many people can use a machine at the same time
• File and process
• Almost everything (data, directory, process, hard
  disk) are expressed as a file
• Process is an running program identified by a
  unique id (PID)

13
Basic Commands

• When you interact with shell, you will sees the
  prompt, something likeking_at_my_pc
• A command consists of three parts, i.e. command
  name, options, arguments
• king_at_my_pc command-name optionA optionB
  arg1 arg2
• Options always start with -
• Examplecd ..ls l .bashrcmv fileA fileB

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Basic Commands

• ls show files in current position
• cd change directory
• cp copy file or directory
• mv move file or directory
• rm remove file or directory
• pwd show current position
• mkdir create directory
• rmdir remove directory
• less,more display file contents
• man display online manual

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Basic Commands

• su switch to superuser
• passwd change password
• mount mount file system
• umount unmount file system
• df show disk space usage
• ps show current processes
• shutdown reboot or turn off machine
• grep XXX show lines matching pattern XXX in
  File

16
Relative and Absolute Path

• Path means a position in the directory tree
• Two ways to express a path
• Relative path expression the path depends on the
  current directory
• . the current directory
• .. the parent directory
• pwd gives the current path
• Absolute path expression the path is defined
  uniquely from the root /home/linux/ /linux (
  home directory/linux)

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Other Features of Shell

• Take bash as an example
• It supports history, command line editing,
  customization
• Start up .bashrc, .cshrc
• Environment variables PATH, PS1, SHELL,
  TERM, EDITOR, HOME
• Moving around ?, ?, Home, End
• Previous commands ?,?, !!, !1, !2, !x
• TAB ? shell ?????????
• ??????????,????,shell ???????????????????
• ????????

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Other Features of Shell

• Wildcard
• ? a single character
• zero or more characters
• b-d either b, c, or d
• fconf, locg either conf or loc
• Examplels -d /etc/b-h??.conf,loc??
• c (ctrl-c) kill the command
• d (ctrl-d) end the input

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Redirect and Append

• Redirect and append
• Output of command is displayed on screen
• Use gt to redirect the output from screen to a
  file
• Use gtgt to append the output to bottom of the
  file
• Three types of input/output
• Standard input ??? 0,??? lt ? ltlt
• Standard output ??? 1,??? gt ? gtgt
• Standard error ??? 2,??? 2gt ? 2gtgt
• ????????
• ????????????
• ??????? ?,?????????
• ?????? ???,?????????

20
Pipe

• Pipe
• Some commands require input from a file or other
  commands
• Use to use output from another command as
  input to the command
• Example ls /etc/ sort nl gt file1.txt

21
Permission

• All of files and directories have owner and
  permission
• Three types of permission readable, writeable
  and executable
• Permissions are given to three kinds of group
  owner, group member and others
• Example
• ls -l .bash_profile
• -rw-r--r-- 1 cnotred 191 Jan 4 1311
  .bash_profile
• rreadable, wwritable, x executable

22
Permission

• Command
• chmod change file mode, add or remove
  permission
• chown change owner of the file
• Example
• chmod aw filename
• add writable permission to all users
• chmod o-x filename
• remove executable permission from others
• chmod ax
• Gives permission to the user to execute a file
• u user (owner) g group o others a all

23
Process Management

• Process is a unit of running program
• Each process has some information, like process
  ID, owner, priority, etc
• Example Output of top command

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Process Management

• kill stop a program
• The program is specified by process ID
• killall stop a program
• The program is specified by command name
• ps show process status
• top show system usage statistics

25
Foreground and Background

• Running job has two modes, foreground and
  background
• Background job the program keeps running even
  after your session was closed
• Foreground job
• ctrl-c stop program
• ctrl-z let program go into background
• To run programs in background mode king_at_my_pc
  command
• To get background job back into foreground
  king_at_my_pc fg

26
Remote Login and File Transfer

• rshd, telnetd, ftpd, sshd are server program to
  provide remote login and file transfer
• Remote login and file transfer are based on
  server and client model. Client program on your
  machine ask sever program certain service remote
  machine.
• Sample client programs
• WS FTP FTP client
• Internet Exploror HTTP client
• Eudora POP, SMTP client

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Text Editor vi

• vi ???????
• ????
• ????
• ???????

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Text Editor vi
?? (??) ?? ?? (??) ??
i ???????????
I ?????????
a ???????????
A ?????????
o ??????????
O ????????????
ESC ?????????
29
Text Editor vi
???? ????
0 ?????
1G ?????
?????
G ?????
w ????????
x ??????????
X ???????????
30
Text Editor vi
???? ????
NUM ???NUM??
y ??
y y ?????
d ??
d d ?????
d 0 ???????
d ???????
31
Text Editor vi
???? ????
d 1G ???????
NUM .. .. 3 d d ????
.. NUM .. d 3 w ?????
r ????????
x ?? / ??
p ??
u ?????????
32
Text Editor vi
????? ?????
e ????
w ????
w q ??????? (?x???ZZ?)
w q ! ???????????
q ?????
q ! ?????????
33
Text Editor vi
????? ?????
/ ???? (n ????)
s/old/new/g ???? old ??? new
1,30s/old/new/g ?????????????? old ??? new
1,s/old/new/g ???????? old ??? new
1,s// /g ??????????????
34
Install Software

• Unix system has a de facto standard way to
  install a softwareconfigure ? make ? make
  install
• Typical software installation procedure as
  following
• Download source code Usually, its archived with
  tar command and compressed with gzip command
• Configure command creates Makefile automatically
  which is used to compile the source
• Program compilation is written in Makefile

35
Install Software

• gzip compress a file
• gunzip uncompress a file
• tar archive or expand files
• configure create Makefile
• make compile and install software
• Example
• gunzip software.tar.gz
• tar xvf software.tar
• cd software
• ./install OR make all OR