Linux Introduction

1
Linux Introduction

• What is Linux?
• How do you use it?

2
Outline

• Linux Background
• Linux Basic Structure
• Linux User Interface
• Linux Commands

3
History

• 1991 - Linus Torvalds (Finnish student) looked
  for a development version of UNIX (other than
  Minux).
• Objective was to develop an open source version
  of UNIX that was functionally identical, but
  source code independent (as a hobby)
• Focus on the core operating system (the kernel)
• Project took on its own life. Version 1.0
  released March, 1994

4
Design Capabilities

• Multi-tasking
• Multi-user
• Multi-processing (multiple processors)
• Architecture Independence
• File system Flexibility
• Paging
• Memory Protection (protected mode)
• Networking

5
Kernel vs Distribution

• Kernel provides core OS functionality
• managed by Linux.org (Torvalds, et.al.)
• Distribution provides installation and package
  management needed to implement a complete OS
  including applications
• Red Hat (Fedora)
• CentOS
• Ubuntu
• SuSe
• Debian
• many others

6
System Organization

• Like UNIX...
• Predefined root directory structure with
  preferred locations for kernel files

/ (root)
bin
dev
home
mnt
root
tmp
var
boot
etc
lib
proc
sbin
usr
7
System Organization
Directory Purpose
/ The root directory, which is the top of the file system.
/bin Critical executables needed to boot the system.
/dev Devices connected to the system, such as terminals, disks, tapes, modems, etc.
/etc System configuration files, including passwords, network addresses and names, system start-up settings, etc.
/home Location of users directories.
/lib The home of various shared libraries for programs.
8
System Organization
Directory Purpose
/mnt The point where file systems exported from another system are temporarily mounted.
/proc Images of currently executing processes on the system.
/tmp Temporary files that are cleaned up during the boot operation.
/usr A variety of system files, including standard system utilities (/usr/bin), manual pages (/usr/man), headers for C programs (/usr/include), and administration executables (/usr/sbin).
/var Directory that stores log files (/var/log) and temporary storage space for services (such as spooling for mail, printers, etc.).
. Current directory.
.. The directory just above the current directory.
9
Linux Security

• File Level Security
• Authentication - allow only authorized users into
  the system (user name, password)
• Access control - Ensure that resources (files)
  are only used by authorized users. (user id,
  group id, mode bits)
• System Level Security
• Many of the same weaknesses as UNIX, since the
  basic design is the same
• Open source
• Makes it easy for hackers to analyze the system
• Easy for testers to fix the system when bugs are
  found.

10
User Interface Options

• Command Line Interface
• Primitive Interface that requires little system
  support
• Used on Embedded systems, old systems, some
  servers
• All Linux (UNIX) functions (commands) originally
  developed for command line.
• Commands defined in man 1
• (See also Running Linux)
• Change to GUI with startx

11
User Interface Options

• Graphical User Interface
• Based on X Windows System
• X Server to generate display (bitmap)
• X Client to present display to Video monitor
• Manages basic graphical display configuration
• Display Resolution
• Monitor type
• Video Card
• Input Devices
• Use Window Managers to provide GUI

12
User Interface Options

• GNOME
• GNU Network Object Model Environment
• Uses Enlightenment or Sawfish WM
• Based on CORBA Architecture to support
  interaction between objects (applications,
  components, etc.)
• Uses Nautilus File Manager

13
User Interface Options

• KDE
• K Desktop Environment
• Heavy use of Drag-and-drop
• Includes Kongueror File Manager
• Integrates local file management with Web
  browsing
• Often extensive list of K applications and
  applets available.

14
Commands

• Installation / Update
• Schedule Programs / Jobs
• Check / Change Environmental Variables
• Manage Processes

15
Installation / Update

• Based on packages that include all files
  associated with an application / function
• Includes configuration information directory
  locations, linkage to existing system config
  files.
• Most common is rpm Red Hat Package Manager
• Developed by Red Hat, but supported by many Linux
  Distributions
• Provides a method to test, verify, install,
  uninstall or upgrade software (packages)

16
Automatically Schedule Programs
17
Manually Schedule / Run Programs

• cron
• System program that will schedule jobs
• crontab
• Users controlled by /etc/cron.allow or
  /etc/cron.deny
• Specify H Min D Mon DOW command
• crontab
• 5 1,15 echo turn in timesheets! mail
  cotterr
• ltEOTgt D

18
Manually Schedule / Run Programs

• at
• Users controlled through /etc/at.allow or
  /etc/at.deny
• Specify time date of execution
• provide list (file) of commands / jobs to execute
• at 1121 Jan 5
• atgt /home/cotterr/bin/myscript.sh
• atgt cp /home/cotterr/info.txt /home/backup/info.tx
  t
• atgt ltEOTgt D

19
Environmental Variables

• printenv
• Display all environmental variables
• echo PATH
• Display the contents of a single variable
• set PATHPATH/sbin
• Temporarily add /sbin to search path
• set
• Display all current variables

20
Manage Processes

• ps
• Print status of all of your active processes
• ps aux
• Print status on all active processes
• kill s 9 PID
• Terminate a process with process id PID

21
SUMMARY

• Linux Background
• Linux Basic Structure
• Linux User Interface
• Linux Commands