INTRODUCTION TO LINUX


Linux is said to be the world's fastest growing operating systems because of it's diverse functionality, effeciency and capabilities.
Linux was developed from another operating system called UNIX.
Linux was first developed in USA by Linus in the early 80's.
However, today Liux is the most common operating system used by high end servers.
Linux was developed because Unix was not user friendly, it had no GUI(Graphical User Interface) hence it could only work with the Command line and to do anything with it some had to execute only commands.
Unlike for Microsoft Windows, Linux comes as both a desktop and a network opearating system ,the system incorporates tool which can be used for diverse activities like computer programing, software development and other heavy computing operations while for Windows, it developes different operating systems for different tasks.
UNIX has various flavours.
They include:
Caldera


Linux also has various flavours/brands. They include
Linux Red Hat
Suse Linux
Sam Linx
Fedora
Ubuntu
Mubuntu Linux
Linux Mint
Debian
Cairos Linux
e.t.c
 The brands of Linux can never get exhausted in that, Linux is open source meaning that any one can edit anything in the operating sytem but the task is to advertise world over, if the change is liked by the people it will become acceptable and coppies of that editorial will circulate all over the world.
This is the very reason why there are so many Linux flavours on the market today.
LINUX KEYBOARD SHORTCUT KEYS

Linux usage in everyday life

You can use Linux as a server operating system or as a stand alone operating system on your PC. As a server operating system it provides different services/network resources to a client. A server operating system must be:

• Stable
• Robust
• Secure
• High Performance

Linux offers all of the above characteristics plus it is free and open source. It is an excellent operating system for:

• Desktop computer
• Web server
• Software development workstation
• Network monitoring workstation
• Workgroup server
• Killer network services such as DHCP, Firewall, Router, FTP, SSH, Mail, Proxy, Proxy Cache server etc

What is the Linux Kernel?

The kernel is heart of the Linux operating system. It manages the resources of Linux. Resources include:

• File management
• Multitasking
• Memory management
• I/O management
• Process management
• Device management
• Networking support including IPv4 and IPv6
• Advanced features such as virtual memory, shared libraries, demand loading, shared copy-on-write executables etc

The kernel decides who will use these resources and for how long and when. It runs your programs or sets up to execute binary files.

The kernel acts as an intermediary between the computer hardware and various applications.

BASIC COMPUTER REQIREMENTS FOR LINUX
Because we don’t live in an ideal world, we’ll assume you know little about your PC and need a primer on its components. We’ll run down both the minimal and ideal Linux PC configurations and then give a compatibility list.

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NOTE:  When buying a PC, the temptation is to spend as little as possible or to try to squeeze by with lesser or inferior components. We understand the need to live on a budget—we certainly don’t have thousands of dollars worth of computer equipment sitting around our home offices. But there comes a point when you need to make the necessary investment if you want to run Linux effectively. Too often we see people complaining in the Usenet newsgroups that Linux doesn’t run properly on their PCs or that XFree86 won’t run in higher resolutions on their unsupported graphics cards. You can avoid this by either taking an inventory of your PC before installing Linux (which may mean actually taking off the cover and physically poking through the components) or making sure a new PC meets the compatibility guidelines. Either action is a real pain, we admit; but by spending some time up front, you’ll avoid many problems later in the installation and configuration process. You may be pleased with yourself after saving some cash buying a new graphics card from NoNameClone Corp., but in the end you’re better off paying a little more for hardware that’s been thoroughly tested by the huge number of existing Linux users.

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Table 1.1 lists the minimum and ideal configuration guidelines for Linux.

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NOTE:  If you’re not sure about your particular hardware setup and Linux compatibility, check out the Hardware Compatibility List from Google or the the appropriate Linux flavour you are using on their website.

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WARNING:  Watch out for hardware advertised as “plug-and-play.” Most of this hardware is extremely difficult to use with Linux, although it can be done by first booting DOS and then “warm booting” into Linux with Loadbin. Some experimental kernel patches and a plug-and-play configuration tool are included in Slackware, but in general, if you can avoid plug-and-play devices (at least until Linux support improves) you’ll be better off.

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The Core Components

In the rest of this chapter, we’ll run down the various PC components and warn you about any potential downfalls if you want to use Linux. In addition, you’ll want to check out Chapter 3 for a discussion of supported graphics cards—support that becomes vitally important if you’re looking to run XFree86 (the implementation of the X Window System) with Linux.

In this section, we’ll begin with a rundown of the basic components of your computer: bus, processor, and so on.

Bus

Linux runs on all the major bus architectures—ISA, VLB, PCI, EISA—except for the nonstandard Micro Channel Architecture, found on most IBM PS/2 models. (Not every IBM PC features an MCA bus, luckily; the ValuePoint and PS/1 models feature an industry-standard ISA bus.)

Processor

Linux needs at least an Intel 80386-based processor in order to run efficiently. Don’t bother with a 80286-based PC. If you’ve got an older PC sitting in the closet and you think it might be neat to recycle by using Linux, leave it there, donate it to your local charity, or give it to the kids to bang on. It won’t be useful in your Linux adventure.

Basically, any PC built around the Intel 80386 or better (including the i486, and Pentium, and chips from AMD and Cyrix) is capable of running Linux. If there is no math coprocessor (which may be an issue in older 80386-based PCs), Linux has built-in FPU emulation.

A Few CPU Problems

There are a few reported instances of Linux conflicting with a CPU or math coprocessor:

•  Some AMD 486DX CPUs may hang in very specific situations, a problem that’s not unique to Linux. If this happens to you, contact your PC vendor and get a replacement chip.

•  Some older math coprocessors from Cyrix, IIT, and ULSI (the Math*Co series) have problems with the FSAVE and FRSTOR instructions, which may cause problems with Linux. Again, you can get a replacement chip from your PC vendor.

An A-Z Index of the Linux BASH command line

alias    Create an alias
apropos  Search Help manual pages (man -k)
awk      Find and Replace text, database sort/validate/index
break    Exit from a loop
builtin  Run a shell builtin
bzip2    Compress or decompress named file(s)

cal      Display a calendar
case     Conditionally perform a command
cat      Display the contents of a file
cd       Change Directory
cfdisk   Partition table manipulator for Linux
chgrp    Change group ownership
chmod    Change access permissions
chown    Change file owner and group
chroot   Run a command with a different root directory
cksum    Print CRC checksum and byte counts
clear    Clear terminal screen
cmp      Compare two files
comm     Compare two sorted files line by line
command  Run a command - ignoring shell functions
continue Resume the next iteration of a loop
cp       Copy one or more files to another location
cron     Daemon to execute scheduled commands
crontab  Schedule a command to run at a later time
csplit   Split a file into context-determined pieces
cut      Divide a file into several parts

date     Display or change the date & time
dc       Desk Calculator
dd       Data Dump - Convert and copy a file
ddrescue Data recovery tool
declare  Declare variables and give them attributes
df       Display free disk space
diff     Display the differences between two files
diff3    Show differences among three files
dig      DNS lookup
dir      Briefly list directory contents
dircolors Colour setup for `ls'
dirname  Convert a full pathname to just a path
dirs     Display list of remembered directories
du       Estimate file space usage

echo     Display message on screen
egrep    Search file(s) for lines that match an extended expression
eject    Eject removable media
enable   Enable and disable builtin shell commands
env      Environment variables
ethtool  Ethernet card settings
eval     Evaluate several commands/arguments
exec     Execute a command
exit     Exit the shell
expand   Convert tabs to spaces
export   Set an environment variable
expr     Evaluate expressions

false    Do nothing, unsuccessfully
fdformat Low-level format a floppy disk
fdisk    Partition table manipulator for Linux
fgrep    Search file(s) for lines that match a fixed string
file     Determine file type
find     Search for files that meet a desired criteria
fmt      Reformat paragraph text
fold     Wrap text to fit a specified width.
for      Expand words, and execute commands
format   Format disks or tapes
free     Display memory usage
fsck     File system consistency check and repair
ftp      File Transfer Protocol
function Define Function Macros

gawk     Find and Replace text within file(s)
getopts  Parse positional parameters
grep     Search file(s) for lines that match a given pattern
groups   Print group names a user is in
gzip     Compress or decompress named file(s)

hash     Remember the full pathname of a name argument
head     Output the first part of file(s)
history  Command History
hostname Print or set system name

id       Print user and group id's
if       Conditionally perform a command
ifconfig Configure a network interface
import   Capture an X server screen and save the image to file
install  Copy files and set attributes

join     Join lines on a common field

kill     Stop a process from running

less     Display output one screen at a time
let      Perform arithmetic on shell variables
ln       Make links between files
local    Create variables
locate   Find files
logname  Print current login name
logout   Exit a login shell
look     Display lines beginning with a given string
lpc      Line printer control program
lpr      Off line print
lprint   Print a file
lprintd  Abort a print job
lprintq  List the print queue
lprm     Remove jobs from the print queue
ls       List information about file(s)
lsof     List open files

make     Recompile a group of programs
man      Help manual
mkdir    Create new folder(s)
mkfifo   Make FIFOs (named pipes)
mkisofs  Create an hybrid ISO9660/JOLIET/HFS filesystem
mknod    Make block or character special files
more     Display output one screen at a time
mount    Mount a file system
mtools   Manipulate MS-DOS files
mv       Move or rename files or directories

netstat  Networking information
nice     Set the priority of a command or job
nl       Number lines and write files
nohup    Run a command immune to hangups
nslookup Query Internet name servers interactively

passwd   Modify a user password
paste    Merge lines of files
pathchk  Check file name portability
ping     Test a network connection
popd     Restore the previous value of the current directory
pr       Prepare files for printing
printcap Printer capability database
printenv Print environment variables
printf   Format and print data
ps       Process status
pushd    Save and then change the current directory
pwd      Print Working Directory

quota    Display disk usage and limits
quotacheck Scan a file system for disk usage
quotactl Set disk quotas

ram      ram disk device
rcp      Copy files between two machines.
read     read a line from standard input
readonly Mark variables/functions as readonly
remsync  Synchronize remote files via email
return   Exit a shell function
rm       Remove files
rmdir    Remove folder(s)
rsync    Remote file copy (Synchronize file trees)

screen   Terminal window manager
scp      Secure copy (remote file copy)
sdiff    Merge two files interactively
sed      Stream Editor
select   Accept keyboard input
seq      Print numeric sequences
set      Manipulate shell variables and functions
sftp     Secure File Transfer Program
shift    Shift positional parameters
shopt    Shell Options
shutdown Shutdown or restart linux
sleep    Delay for a specified time
sort     Sort text files
source   Run commands from a file `.'
split    Split a file into fixed-size pieces
ssh      Secure Shell client (remote login program)
strace   Trace system calls and signals
su       Substitute user identity
sum      Print a checksum for a file
symlink  Make a new name for a file
sync     Synchronize data on disk with memory

tail     Output the last part of files
tar      Tape ARchiver
tee      Redirect output to multiple files
test     Evaluate a conditional expression
time     Measure Program running time
times    User and system times
touch    Change file timestamps
top      List processes running on the system
traceroute Trace Route to Host
trap     Run a command when a signal is set(bourne)
tr       Translate, squeeze, and/or delete characters
true     Do nothing, successfully
tsort    Topological sort
tty      Print filename of terminal on stdin
type     Describe a command

ulimit   Limit user resources
umask    Users file creation mask
umount   Unmount a device
unalias  Remove an alias
uname    Print system information
unexpand Convert spaces to tabs
uniq     Uniquify files
units    Convert units from one scale to another
unset    Remove variable or function names
unshar   Unpack shell archive scripts
until    Execute commands (until error)
useradd  Create new user account
usermod  Modify user account
users    List users currently logged in
uuencode Encode a binary file 
uudecode Decode a file created by uuencode

v        Verbosely list directory contents (`ls -l -b')
vdir     Verbosely list directory contents (`ls -l -b')
vi       Text Editor

watch    Execute/display a program periodically
wc       Print byte, word, and line counts
whereis  Report all known instances of a command    
which    Locate a program file in the user's path. 
while    Execute commands
who      Print all usernames currently logged in
whoami   Print the current user id and name (`id -un')
Wget     Retrieve web pages or files via HTTP, HTTPS or FTP

xargs    Execute utility, passing constructed argument list(s)
yes      Print a string until interrupted

.        Run a command script in the current shell
###      Comment / Remark