Introduction to Linux

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Introduction to Linux
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Introduction to Linux

• What is Linux, and Who Created it?
• GNU and the GPL
• Unix/GNU, What is the Difference?
• POSIX Compliance
• Other POSIX Operating Systems
• Uses of Linux
• Advantages and Disadvantages

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What is Linux

• Linux is a UNIX clone
• It can run on 32 bit and 64 bit hardware
• Linux is a true multitasking environment
• Fully capable of taking advantage of multiple
  processors
• Can address up to 64 GB of RAM
• Partial POSIX Compliance

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Penguin Power

• Linux is free
• Anyone can download and compile the source
• The code can be modified by anyone provided the
  modifications are released to the community

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History

• The history of Linux began with Unix in 1969
• Unix was created at Bell Labs with the goals
• Simplicity
• Recycleable code
• Written in C as opposed to assembly
• Development started in 1991
• Linus Torvalds wanted to create a free
  implementation of UNIX
• By 1993 there were 12000 Linux users
• Today Linux rivals UNIX in stability and
  scalability

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The Kernel

• Linux is not an Operating System
• Linux is a kernel

• A kernel is a program that allocates and controls
  hardware resources in a system

• Linux Distrobutions use the Linux kernel together
  with the GNU Operating System

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The Linux Kernel

• The Linux kernel is currently maintained by Linus
  Torvalds and a few hundred other developers
• Releases are numbered in a very ordered fashion.
• Major.minor.patchlevel
• Odd minor numbers are development kernels
• Thus
• 2.4.20 latest stable kernel
• 2.5.67 latest development kernel
• Will become the 2.6 kernel

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Design

• The Linux kernel has a monolithic design
• The other approach is the microkernel design
• Both have their upsides and downsides
• Monolithic kernels
• Easier to build and design
• Generally faster
• More recompiles
• Less object oriented
• Micro kernels
• Considered safer
• Easier to develop drivers for
• Only recompile for upgrades
• Generally slower
• Much harder to build and design

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Other NIX Kernels

• The BSD kernel
• This is the kernel used by the open source BSD's
• FreeBSD, OpenBSD, NetBSD
• It is neither GNU nor GPL
• The GNU HURD
• Hird of Unix Replacing Daemons
• Hurd of Interfaces Representing Death
• The world's first doubly recursive acronym
• Micro kernel
• Not very functional

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Isn't a GNU an Animal?

• GNU stands for GNU Not Unix
• The goal of GNU
• Create a free and complete UNIX-like operating
  system
• This has been in development since 1984
• Towards this goal the GNU project has released
• GCC, GNU Emacs, Bash, to name a few
• For more information see the GNU Manifesto
• http//www.gnu.org/gnu/manifesto.html

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What is the GNU GPL?

• The GNU General Public License
• Ensures that GNU software stays free
• This is done through Copy Lefting
• Any modification to GPL software is required to
  be released to the public
• Linux is released under the GPL
• Due to its restrictive nature the GPL has
  recently come under fire
• http//www.linux.org.uk/GPL.html

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Does the GPL Matter?

• Depends on your point of view
• Not as important for users
• Very important for developers
• Any GPL code that is incorportated into a program
  makes the entire program GPL
• No closed source software can use any GPL software

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So Unix Costs Money and GNU/Linux is Free

• Essentially this is the case
• Both have the goals of POSIX compliance
• Commercial UNIXes are in general closer
• This is generally in implementation, not in use
• Commercial UNIXes generally perform better in
  large systems
• But even this is difference is shrinking
• The biggest difference is that UNIX is
  trademarked and must be commericialnot free

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POSIX? Another Operating System?

• Nope, its yet another acronym
• Portable Operating System Interface
• POSIX is a set of specifications
• Describes how the operating system should behave
• Both to the user, and to other programs
• POSIX was created to combat the plethora of
  UNIXes that popped up in the 1980, all of which
  had a different look and feel

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POSIX cont...

• The Open Group controls the UNIX trademark
• They also release their own UNIX specification
• The latest POSIX specification has been merged
  with the Open Group's UNIX specification
• For more information see
• http//www.pasc.org
• http//www.opengroup.org/

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Other POSIX OSes

• IBM AIX
• Sun Solaris
• SGI IRIX
• HP HP--UX
• Compaq TRU64 UNIX

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So Why Should I Use Linux?

• As a server platform
• few other operating systems can match Linux in
• Performance
• Price
• Stability
• For Developers
• Resources
• Linux has a tremendous number of tools available
  for developers. And they are all free.
• For the Desktop
• It's fun

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Advantages

• Linux is free
• Can't say that enough
• It's great for poor college students
• Learning Linux means learning UNIX, and UNIX is
  the largest server platform in the world
• Community
• The Linux community is very active and helpful
• This makes support very rapid

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But it's hard to learn

• Linux is much harder than Windows
• It's harder to use than Windows
• It lacks all those great automated installation
  tools
• You have to manually configure hardware
• There is lots of hardware out there that just
  won't run in Linux

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So You Are Ready to Take the Plunge

• What do I need to know?
• Not all distros are the same
• Linux From Scratch is a bad starting place
• Internet Resources
• www.linux.org
• www.tldp.org
• www.justlinux.org
• www.desktoplinux.org
• What distro should I start with?
• Redhat
• Mandrake
• Suse

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Some Linux Basics

• File System
• Linux is much more hierarcal than Windows
• Everything starts at the root
• /
• Boot -- contains the kernel and system map
• Bin -- contains the basic system binaries
• Dev -- all the device entries
• Etc -- can't think of any other place to put it
• Home -- where all the users live
• Lib -- system libraries
• Mnt -- place to mount filesystems
• Proc -- system information
• Root -- the root user's home
• Sbin -- system binaries
• Usr -- where user accessible programs go
• Var -- logs and such

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Basics cont...

• CLI
• The command line interface
• Bash is the most common shell
• The CLI in Linux is quite useable
• Navigation
• ls -- lists files and directories
• cd -- changes directories
• rm -- removes files
• Navigation switches
• Most programs have options that you can pass to
  them via switches, for ex. ls -h gives you all
  the options that ls can take and what they
  do

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6 Runlevels

• Level 0
• Halt
• Level 1
• Single User mode
• Level 2
• Reserved
• Level 3
• Full Mulituser
• Level 4
• Reserved
• Level 5
• Xwindows
• Level 6
• Reboot

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XWindows

• Linux Graphical Environment
• Invoked via the startx command
• Two major environments
• KDE
• Gnome
• The difference is primarily in philosophy
• Redhat trys to erase the differences with
  Bluecurve
• Does everything Windows does and more

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A Few Good Distros

• Redhat
• Mandrake
• Suse
• Lycoris
• Gentoo
• Knoppix

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Hat's off

• Redhat
• Pros
• Easy install
• Tons of graphical tools
• Great hardware support
• One of the most mature distros
• Cons
• It's slow
• Their stock kernel is somewhat bloated
• Installs files in non-standard directories
• Not customizeable

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Drako

• Mandrake
• Based on Redhat
• Modified to suit desktop systems more than Redhat
• Supports that funky DVD Decoder Card you have to
  use
• More on the edge than Redhat
• Uses a modified kernel

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Tame the Lizard

• Suse
• Pros
• Avoids much of the bloat of Redhat and Mandrake
• Great hardware support
• The easiest Linux installation I have ever had
• Cons
• Still hard to customize

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Perfection

• Gentoo
• Pros
• Builds Linux from scratch, optimizing for the
  architecture of your PC
• Blazing speed
• Highly customizeable
• User Forums are a great place for support
• Runs Quake and Unreal Tournament 2003 out of the
  box
• Has a kernel specifically modified for gamers
• Cons
• Can be overwhelming
• Takes a long time to build
• Do not trip over the power cable while it is
  building

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Knoppix

• Self contained
• Can boot almost any pc that supports cdrom
  booting
• Settings can be stored locally or on USB pen
  drive
• Great to learn on
• Does not require resizing partions or wiping
  drives