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Linux Overview

Presented by Ben McMillian on September 3, 2003

Table of Contents


1. Basics


1.1. What is Linux?

Although most people refer to Linux as an operating system, it really
isn’t. Specifically, Linux is just the core of the operating system,
called the ‘kernel’, which runs the applications and interacts with the
hardware. The Linux kernel was originally written by Linus Torvalds in
1991, but now includes code from thousands of programmers worldwide.
This kernel is then combined with many applications and utilities and
collectively form the OS commonly known as Linux (or GNU/Linux).


1.2. What are ‘distributions’?

There are many applications (aka, packages) out there. Some do the same
things as others, and most are available in different versions.
Companies such as Red Hat, Mandrake, Gentoo, etc take the kernel and
package it with their own choice of applications. The big companies also
usually modify the kernel and write custom applications (mostly
configuration utilities). These companies also spend a lot of time
writing installers, so that installing Linux isn’t as hard and scary as
it used to be.

These compilations of applications, installers, and kernels are called
distributions. There are dozens of distributions available and most are
free to download. Some can be purchased, although you usually are paying
for the packaging, printed documentation, and tech support.

Different distributions are geared for different kinds of users.
Mandrake is great for previous Windows users who are new to Linux. Red
Hat is also good for these types of users, although it suits the more
advanced users a little bit more than Mandrake. Red Hat has many
different versions, just as Microsoft has many different versions of
Windows, all to suit different users. The "enterprise" editions are
especially designed for businesses installing it on servers and such,
whereas the normal "desktop" editions are for normal (web surfing, word
processing, etc) users. Some versions are especially designed for
international users. Some distributions are meant to fit on (and totally
run from) a floppy or a CD.

The most well-known distributions are (in no particular order):
Red Hat, Mandrake, SuSE, Gentoo, Slackware, Debian, Knoppix


1.3. GPL

Linux and many of the applications that come with the ‘Linux’ operating
systems are released under the Gnu Public License. This means you can do
whatever you want with them – use them, copy them for a friend, change
them, etc. However, do not falsely claim that you wrote the entire app
or kernel, and any changes that you’ve made need to be shared with the
community. This makes it possible for everyone to contribute.


1.4. Who operates, owns, controls Linux?

Unlike Windows, which is controlled by Microsoft, Linux is not owned or
controlled by a large corporation. In fact, there is no single entity in
charge of Linux. Instead, Linux is by and for hobbyists, hackers, and
professionals worldwide.

However, Linus does own the name, "Linux," and Larry Ewing the official
mascot,"Tux."


2. Why Linux?

  • Have you ever used Unix and liked its simplicity and power?
  • Do you enjoy [the idea of] reading source code of programs to see how
    they function?
  • Do you have a class need for a good C, C++, gcc, make environment?
  • Do you want to run a great website with just a few simple (yet
    powerful) tools (vi, make, perl, apache, etc)?
  • Do you not want to use monopolistic over-bloated buggy and expensive
    proprietary OS’s?
  • Do you like to have many different ways to do anything?
  • Do you want to be cool?
  • Do you believe you can evolve into a superior technical lifeform?
  • Do you want any kind of technological job 10+ years from now?

If ANY of these applied to you, Linux is for you.


3. Linux Basics


3.1. Kernel

As said before, the kernel is the middle-man between hardware and
software. It is the kernel that is responsible for handling memory,
processes, hard disk I/O, ethernet activity, etc. If you use a wireless
card, your kernel must be able to support the chipset of that card
(prism2, orinoco, etc).

When somebody says they are recompiling their kernel, it is usually
because they bought a new gadget, patched the kernel to protect themself
from an exploit, or just need a new feature (like iptables support).
Typical Linux kernels are usually 1-4mb in size. Some people try to
enable support for only those things they already have, and nothing
else, to try to reduce the filesize(so they can fit it on a floppy).
Other people enable support for anything they think they might want in
the future to avoid having to recompile their kernel.

However, there is a way to enable support for a new feature or gadget
without recompiling your kernel (and thus forcing you to reboot into
that new kernel). You can either build support into the kernel, or as a
module. Modules are separate from the kernel, and can be loaded and
unloaded at will. All you have to do is tell the kernel config utility
that you want that driver compiled as a module (outside of the kernel),
run "make modules modules_install" and voila. Load that module("modprobe
ewmodule") and magically you have support for that new device. No reboot
was required. This saves a lot of time and trouble.


3.2. Filesystem

The Linux filesystem is a lot different than that of Windows. Windows
uses drive letters for drives (hard drives, CD roms, floppies, etc) and
partitions for those drives. C: is the root for the primary (and maybe
only) hard drive or partition. D: is the root for the secondary hard
drive. So on and so forth. Linux, on the other hand, has only 1 root.
The root directory is "/". Everything resides in this root.

/ (root)
|
+------+-----+------+-----+-----+-----+-----+-----+-----+------+-----+
/boot/bin/home/mnt/lib/var/usr/dev/etc/proc/root /tmp

There are more dirs than those listed above, but that’s most.

/home is where users’ home directories are located. /home/daevux will be
where user daevux will put all their files, pictures, etc.

/mnt is where you would "mount" a drive, partition, or any other storage
device. For instance, /mnt/cdrom is the most typical place for where you
would "mount" your cdrom drive. First, what is "mount" ? When you mount
a drive, you are telling Linux to get that drive ready for I/O. Linux
then determines what filesystem the drive is formatted with(iso9660 for
CDs, vfat for Windows drives, smbfs for samba shares, etc), then figures
out how it should interact with it accordingly.

/etc is where most system-wide configuration files are kept. For
instance, /etc/apache/conf/apache.conf is the configuration file for
Apache.

/boot is where the kernel is kept, as well as any bootloader (grub,
lilo).

/lib contains the libraries needed for certain programs to be run. This
is also where kernel modules are kept.

/var is usually for log files, sometimes tmp files, email spools, etc.

/usr is where applications and user utilities are located, in addition
to A lot more stuff.

/root is the home directory for the root user.

/tmp is for temp files.

/bin (and /sbin) contains basic system utilities (bash, cd, dd, halt,
etc)

/dev and /proc are not real directories. /proc includes system
information (a lot of statistics, etc). /dev includes "pointers" per se to
hardware devices. /dev/mouse is a pointer to your mouse. /dev/hda1 is a
pointer to the first partition on your primary hard drive. There’s also
stuff like /dev/zero, /dev/null, and /dev/random.


3.3. Permissions/Users

Linux (like most modern OSs) is multiuser. This means that many users
can use the system, even at once.

First and foremost, there is only 1 root. This is the ultimate superuser
of the machine. root can do anything and everything. Keep root’s
password safe!

Then there are normal users. Users can belong to certain groups, which
determine that user’s capabilities. For instance, a user in the wheel
group is allowed to "su" (switch to root mode) on a Gentoo system (I
don’t know if this is true for all distros). Most users should be
included in the group, "users".

Every file and directory in Linux has attributes that determine who can
read, write, and execute it. For instance, file xyz.txt might have have
permissions that look like this (using ls -o): -rwxr-xr-x . the first
character determines what type of object it is (file, dir, sym link,
etc). – means it is a file. d will mean it is a directory. The next 3
characters are for user, the next 3 for group, the next 3 for all users.
This particular file can be read and executed by the user who owns it,
the users in that user’s group, and everyone. However, only the user who
owns it can write/modify it. The "chmod" command changes those
permissions (but must be run by either the user who owns it, or root).
The "chown" command changes the ownership of the file.


3.4. CLI/Shells

What good is the operating system if you can’t interact with it? This is
where the command line interface (CLI) comes in. This is a generic term
used to describe a text-based way of interacting with programs, as
opposed to using GUIs. It is the simplest way to interact with Linux.

Shells are various programs that provide this functionality. The most
popular shell is bash, but some others are csh, ksh, tcsh, and zsh.
They basically take your commands, process them, execute the program
you called, and display that program’s output. They do much more than
this, but you get the gist of it.

For instance, you might see something like this:

daevux@feynman daevux $

This is a bash prompt. The first word before @ is the username, the word
after the @ is the computer’s [host]name, and the 3rd word is the
current directory. Bash is popular partly because it does (by default)
tab completion and keeps a command history.

{acmey:gtg051h:!}

This is another shell (ksh). Slightly different than bash. Of course,
there is much more difference between the shells than just how the
prompt is formatted.


3.5. X-Windows

X-Windows is for wussiess. Just kidding. X basically allows you to use
Linux in a much more friendly, graphical environment. XFree86 is what
most Linux users use; it is the free implementation of X. There are
other implementations, but XFree86 is the most mature and popular. X is
also a server/client app, meaning you can run X programs remotely.


4. Applications


4.1. Window Managers

X is no good without a window manager running on top of it. Window
managers operate between X and the graphical programs you want to run.
They do stuff like draw the borders around your programs, manage their
placement, draw titlebars, etc. Some WMs are very simple, some are
very complex.


4.1.1. KDE

More than just a WM, KDE is a desktop environment. It resembles Windows
a lot. There is a panel at the bottom, with buttons that execute programs
and expand menus. Also in this panel is a task area, which keeps track
of which programs are open/minimized. Sound familiar? This is the best
WM to use for those new to Linux. Many distros come with this by default.

KDE uses the Qt engine.


4.1.2. Gnome

Gnome is another WM/DE (desktop env). The same comments for KDE also apply
here. Refer to the screenshots to see the differences.

Gnome uses the GTK[2]+ engine.

Note: Gnome (GTK) and KDE (Qt) applications can be run in any WM, not just
the ones they were written for.


4.1.3. Fluxbox/Blackbox

This WM is for more experienced users – those that are annoyed by DEs.
Fluxbox and the WM it was based off of, Blackbox, are minimalistic to some
degree. This means that it only does what is needed. Nothing more. There is
the toolbar, which only includes iconified (minimized) programs, the time,
and the workspace name. There is also the slit, where you can put dockapps –
small graphical programs that monitor time, CPU, Memory, I/O, Network, etc.
Most people that use these WMs rely on keybindings to open programs – in
addition to a small menu. A major selling point to these window managers is
that they’re very fast and very stable. Fluxbox, unlike Blackbox, also
heavily uses tabs – so that you can group windows together.


4.1.4. Enlightenment

Enlightenment is a popular window manager, with an almost cult-like following.
It is the inspiration for many current window managers. The window manager
however hasn’t seen a new release in nearly two years, and is dying out. It is
kind of like Blackbox, but more graphics heavy (prettier) with cool effects.


4.1.5. Window Maker

Window Maker offers a lightweight alternative to GNOME and KDE. It provides
a look-and-feel that mimics the NEXTSTEP user interface, but can be themed any
way you like. Features such as the Dock and Clip make Window Maker a popular
choice among system administrators.


4.2. Office/Productivity

  • OpenOffice
  • KOffice
  • Abiword
  • GnuCash
  • Siag


4.3. Editors

  • Vi/ViM
  • Emacs
  • Pico/Nano
  • SciTE


4.4. Web Browsing

  • Mozilla
  • Konqueror
  • Lynx


4.5. Email/News

  • Evolution
  • Sylpheed
  • KMail
  • Pine
  • Mutt
  • Tin/SLRN/Pan
  • KNews


4.6. Other Internet Stuff

  • Gaim
  • Everybuddy
  • XChat
  • BitchX
  • Kismet
  • P2P stuff
  • gFTP


4.7. Multimedia

  • GQView
  • xv
  • gPhoto2
  • XMMS
  • Timidity++
  • XawTV
  • TVTime
  • MPlayer
  • Xine
  • VLC
  • gCombust
  • gRip


4.8. Games

Sorry, no games for Linux. Just kidding :)

  • GnuChess
  • Quake1-3
  • Halflife
  • TuxRacer
  • BZFlag
  • Dopewars
  • Foobillard
  • Unreal
  • UT2003
  • RTCW
  • Freecraft
  • Freeciv
  • Penguin-command
  • GLTron


4.9. Servers/Databases

  • MySQL
  • PostgreSQL
  • Apache
  • Postfix
  • Sendmail
  • Qmail
  • Samba
  • Cups
  • ProFTPd
  • BIND


5. Useful Links


6. Screenshots

Screenshots can be seen at http://benmcmillan.com/lugpres/images/.

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