LIS651 lecture 5 history and use of GNULinux

1
LIS651 lecture 5history and use of GNU/Linux

• Thomas Krichel
• 2009-04-26

2
Early Computing History

• In the 1940s and 1950s, all computers were
  personal computers in the sense that a user would
  sign up to use the machine and then take over the
  whole machine for that period.
• The early 1960s were dominated by batch systems
  in which a user would submit a job on punched
  cards and wait, usually hours, before any printed
  output appeared.

3
Early Computing History

• To get around this unproductive environment, the
  concept of timesharing was invented by Dartmouth
  College and M.I.T.
• The M.I.T system CTSS (Compatible Time Sharing
  System) was an enormous success.
• M.I.T., Bell Labs, and General Electric created a
  second generation timesharing system named
  MULTICS (Multiplexed Information and Computing
  Service).

4
Early UNIX History

• At Bell Labs, Ken Thompson decided to write a
  stripped down version of MULTICS for the very
  small PDP-7 minicomputer which he called UNICS.
• Dennis Ritchie, also at Bell Labs, joined
  Thompson in further developments of what was now
  called UNIX.
• Together they ported the system the the larger
  and very popular PDP-11/20 and PDP-11/45
  minicomputers.

5
Early UNIX History

• In 1974, Ritchie and Thompson published a paper
  about UNIX and received the prestigious ACM
  Turing Award.
• This publication stimulated many universities to
  request a copies of UNIX.
• Since Bell Labs, part of ATT, was not allowed
  to be in the computer business, it licensed UNIX
  to universities.
• Result UNIX was a hit on campus.

6
UNIX Structure

• The kernel is the core of the UNIX system,
  controlling the system hardware and performing
  various low-level functions. The other parts of
  the UNIX system, as well as user programs, call
  on the kernel to perform services for them.
• The shell is the command interpreter for the UNIX
  system. The shell accepts user commands and is
  responsible for seeing that they are carried out.

7
BSD UNIX

• One of the many universities that had received
  license for UNIX was the University of California
  at Berkeley.
• Aided by many government grants, Berkeley
  released an improved version named 1BSD (First
  Berkeley Software Distribution)?
• BSD added many new features including a new
  visual editor (vi) and a new shell (csh).

8
Two UNIX Versions

• Because of these and other enhancements, many
  companies based their UNIX on Berkeleys version
  as opposed to ATTs so-called System V.
• By the late 1980s, two different and somewhat
  incompatible versions of UNIX were in widespread
  use 4.3 BSD and System V release 3.

9
UNIX Standards

• In addition, every vendor added its own
  nonstandard enhancements.
• In an attempt to unify the troops, the IEEE
  Standards Board undertook the POSIX Project (POS
  for Portable Operating System) and IX to make it
  UNIX like.
• POSIX 1003.1 emerged as a common ground standard.
  
• 1003.1 is the intersection of System V and BSD.
  (a feature had to be on both to be included in
  the standard)?

10
GNU

• GNU is a project started by Richard M. Stallman
  (RMS) to write a completely free implementation
  of Unix available.
• GNU stands for GNU is not Unix
• Most of Unix has been rewritten by him and his
  friends.
• Many other software packages have been released
  for free. Stallman pioneered a particular concept
  of free software.

11
free software according to RMS

• Free software comes with four freedoms
• The freedom to run the software, for any purpose
• The freedom to study how the program works, and
  adapt it to your needs
• The freedom to redistribute copies so you can
  help your neighbor
• The freedom to improve the program, and release
  your improvements to the public, so that the
  whole community benefits

12
the GNU public license

• Richard M. Stallman created the GNU public
  license.
• The license restricts the right of software users
  to add restrictions on the use of derivative
  products.
• The idea is that when you get free software, you
  can not restrict the freedom of users of
  derivative software.

13
UNIX-like Systems

• MINIX, by Andrew Tanenbaum, used a microkernel
  design with only 1600 lines of C and 800 lines of
  assembler in its first version.
• In 1991, a Finnish student named Linus Torvalds
  released another UNIX clone named Linux. It is a
  UNIX kernel for Intel processors.
• FreeBSD is a competitor to Linux, started in 1993.

14
Linux

• Linux is a monolithic UNIX kernel.
• Linux quickly grew in size and functionality.
• Version 1, shipped in 1994, contained about
  165,000 lines of code.
• Version 2 in 1996 contained about 470,00 lines of
  C and 8000 lines of assembler.
• Linux is released under the GNU public license,
  which, very basically means that anyone can copy
  and change it.

15
Linux Distributions

• Linux itself is free. It is aggregated with
  installation and management tools, and many other
  software packages, and made available for a small
  fee by various vendors on CD.
• These aggregates are known as distributions.
• The one used by wotan is called Debian. It
  packages Linux with GNU software almost
  excusively.

16
communication with wotan

• For file editing and manipulation, we use putty.
• For file transfer, we use winscp.
• Both are available on the web.
• The protocol is ssh, the secure shell, based
  public-key cryptography.

17
installing putty

• Go to your favorite search engine to search for
  putty.
• If you have administrator rights install the
  installer version.
• Since you have already installed winscp, you
  should have no further problems.

18
putty options

• In the window/translation choose UTF-8, always.
• Find out what the size of your screen is of
  screen that your are using for the font that you
  are using, and save that in your session.
• For wotan, the port is 22, ssh.
• You can choose to disable the annoying bell.

19
Diffie and Hellman (1978)?

• Let P be the plaintext, C be the cyphertext. E()
  is the encryption key and D() is the decryption
  key.
• Then we have public key cryptography if
• 1. D(E(P))P
• 2. D() can not be broken by chosen plaintext
  attack.
• 3. Knowing E() will give you no clue about D().
• E() can then be made public and is referred to as
  the public key, D() is the private key.
• It is possible to find key pairs that have these
  properties.

20
Authentication

• I want to securely login to a host machine.
• I send the hast an encrypted message hey, I am
  Thomas, my public key is 7ni820g0...''
• Machine then knows how to send me messages that
  other people can not decode.
• But it can not be sure that it was me who sent
  the message. An intruder may have done that since
  me public key is public.
• This problem is solved by challenge/response

21
challenge/response

• To find out if I am the person that I claim to
  be, the machine encodes a random number, and
  challenges me to decode that number.
• If I can decode the challenge, I must be the
  person whom I claim I am.

22
key creation

• ssh-keygen is the command to use to create a
  key. Answer all questions with the ltENTERgt key.
• cd .ssh and ls -l shows you the contents of
  the directory .ssh created in the first step.
• The file id_rsa.pub has your public key.

23
authorized_keys

• In .ssh, you can maintain a file
  authorized_keys that contains the public keys
  of all users you authorize to access the account,
  one line per user.
• cp id_rsa.pub authorized_keys will authorize
  yourself. Then ssh user_at_wotan will allow you to
  login again as you on wotan.
• You can also create a public key with putty.

24
issuing commands

• While you are logged in, you talk to the computer
  by issuing commands.
• Your commands are read by command line
  interpreter.
• The command line interpreter is called a shell.
• You are using the Bourne Again Shell, bash.

25
bash features

• bash allows to browse the command history with
  the up/down arrow keys.
• bash allows to edit commands with the left/right
  arrow keys.
• You can complete command and file names with
  ltTABgt.
• bash comes with a language of commands that
  allows to write batch files.
• exit is the command to leave the shell.

26
environment variables

• These are variables used by the shell.
• Two important ones are
• HOME your home directory
• PATH the location where bash will search for
  executable files.
• echo HOME will show you your home directory.
• env is a command that can be used to see all
  environment variables.

27
environment variables and PHP

• All environment variables can be accessed with
  _ENV'env' in PHP, where env in the name of the
  environment variable.
• Example
• home_ENV'HOME'
• print "my home is home.lt/brgt"

28
bash initialization

• Files that start with a dot are hidden. They are
  only seen with ls -a.
• .bashrc is a file written in bash language that
  is run every time bash is started.
• .bash_profile or .profile is run when the shell
  is started at login.
• You can customize these files.

29
files, directories and links

• Files are continuous chunks data on disks that
  are required for software applications.
• Directories are files that contain other files.
  Microsoft calls them folders.
• In UNIX, the directory separator is /
• The top directory is / on its own.

30
home directory

• When you first log in to wotan you are placed in
  your home directory /home/username
• cd is the command that gets you back to the
  home directory.
• The home directory is also abbreviated as
• cd user gets you to the home of user user.
• cd does what?

31
/public_html

• Is your web directory. I created it with mkdir
  public_html in your home directory.
• The web server on wotan will map requests to
  http//wotan.liu.edu/user to show the file
  user/public_html/index.html
• The web server will map requests to
  http//wotan.liu.edu/user/file to show the file
  user/public_html/file
• The server will do this by virtue of a
  configuration option.

32
changing directory, listing files

• cd directory changes into the directory directory
• the current directory is .
• its parent directory is ..
• ls lists files

33
users and groups

• root is the user name of the superuser.
• The superuser has all privileges.
• There are other physical users, i.e. persons
  using the machine
• There are users that are virtual, usually created
  to run a daemon. For example, the web sever in
  run by a user www-data.
• Arbitrary users can be put together in groups.

34
reason to run things on wotan

• When your run PHP files as a web user, the web
  server runs the PHP file.
• The web server runs as a special user, often
  called www-data.
• This user is not allowed to create files.
• Since file creation and manipulation is the
  essence of digital librarianship, we need to run
  directly on the machine.

35
permission model

• Permission of files are given
• to the owner of the file
• to the group of the file
• and to the rest of the world
• A group is a grouping of users. Unix allows to
  define any number of groups and make users a
  member of it.
• The rest of the world are all other users who
  have access to the system. That includes
  www-data!

36
listing files

• ls lists files
• ls -l make a long listing. It contains
• elementary type and permissions (see next slide)?
• owner
• group
• size
• date
• name

37
first element in ls -l

• Type indicator
• d means directory
• l means link
• - means ordinary file
• 3 letters for permission of owner
• 3 letters for permission of group
• 3 letters for permission of rest of the world
• r means read, w means write, x means execute
• Directories need to be executable to get in them.

38
change permission chmod

• usage chmod permission file
• file is a file
• permission is three numbers, first for owner, 2nd
  for group and 3rd rest of the world.
• Each number is sum of
• 4 for read - 2 for write
• 1 for execute - 0 for no permission
• Example chmod 764 file

39
general structure of commands

• commandname flag --option
• Where commandname is a name of a command
• flag can be a letter
• Several letters set several flags at the same
  time
• An option can also be expressed with - - and a
  word, this is more user-friendly than flags.

40
example command ls

• ls lists files
• ls -l makes a long listing
• ls -a lists all files, not only regular files but
  some hidden files as well
• all files that start with a dot are hidden
• ls -la lists all files is long listing
• ls --all is the same as ls -a. --all is known as
  a long listing.

41
copying and removing files

• cp file copyfile copies file file to file
  copyfile. If copyfile is a directory, it copies
  into the directory.
• mv file movedfile moves file file to file
  movedfile. If movedfile is a directory, it moves
  into the directory.
• rm file removes file, there is no recycling bin!!

42
directories and files

• mkdir directory makes a directory
• rmdir directory removes an empty directory
• rm -r directory removes a directory and all its
  files
• more file
• Pages contents of file, no way back
• less file
• Pages contents of file, u to go back, q to
  quit

43
soft links

• A link is a file that contain the address of
  another file. Microsoft call it a shortcut.
• A soft link can be created with the command
• ln -s file link_to_file where file is a file that
  is already there and link_to_file is the link.

44
file transfer

• You can use winscp to upload and download files
  to wotan.
• If uploaded files in the web directory remain
  invisible, that is most likely a problem with
  permission. Refer back to permissions.
• chmod 644 will put it right for the files
• chmod 755 . (yes with a dot) will put it right
  for the current directory
• is a wildcard for all files.
• rm -r is a command to avoid.

45
editing

• There are a plethora of editors available.
• For the neophyte, nano works best.
• nano file edits the file file.
• nano -w switches off line wrapping.
• nano shows the commands available at the bottom
  of the screen. Note that letter, where letter is
  a letter, means pressing CONTROL and the letter
  letter at the same time.

46
emacs

• This is another editor that is incredibly rich
  and complex.
• Written by Richard M. Stallman, of GNU and GPL
  fame.
• Get an emacs cheat sheet of the web before you
  start it. Or look at next slide.

47
emacs commands

• (here stands for the control character)?
• xs saves buffer
• xc exits emacs
• g escapes out of a troublesome situation
• controlspace sets the mark
• w removes until the mark (cut)?
• y pastes

48
common emacs/bash commands

• k kills until the end of the line or removes
  empty line
• y yank what has been killed (paste)?
• a get to the beginning of the line
• e get to the end of the line
• These commands also work in the shell.

49
emacs modes

• Just like people get into different moods, emacs
  gets into different modes.
• One mode that will split your pants is the PHP
  mode.
• emacs file.php to edit the file file.php in PHP
  mode.
• Then look how emacs checks for completion of
  parenthesis, braces, brackets, and the and use
  the tab character to indent.

50
copy and paste

• Putty allows to copy and paste text between
  windows and wotan.
• On the windows machine, it uses the windows
  approach to copy and paste
• On wotan machine,
• you copy by highlighting with the mouse left
  button
• you paste using the middle button
• if you don't have a middle button, use left and
  right together

51
creating a PHP file

• To run PHP, edit a file with a name ending in
  .php (not required, but useful). Make the first
  lines.
• !/usr/bin/php
• lt?php
• / PHP code goes here /
• ?gt
• The first line less Unix that it has to use PHP
  to run this file. The correct path to the PHP
  executable has to be given.

52
running a PHP file

• You must chmod it executable by you, e.g.
• chmod 755 my_file.php
• where my_file.php is the name of the PHP file.
• Then you can run. But you have to give it the
  full path.
• ./my_file.php

53
running mySQL

• You can run mySQL in command line mode in wotan.
  Type
• mysql -u user -p
• You will then be prompted for your password. The
  username and password are your mySQL user name
  and mySQL password, not your wotan user name and
  wotan password.
• Dont forget the semicolon after each command!

54
login to SQL without password

• You can create a special file .my.cnf in your
  home directory. In there, write something like
• this is a file HOME/.my.cnf
• client
• user username
• password password

55
http//openlib.org/home/krichel

• Thank you for your attention!
• Please switch off machines b4 leaving!