Target Goals

• History and Development of Linux
• Be familiar with the Linux Shell
• Classify Linux documentation by type and use
• Start and Stop the Linux system

Created in 1991 Linux is an OS with commands similar to UNIX

Linux is an open-source OS allowing for a low cost, easy licensing, easily customizable operation with excellent performance and stability.

However, there aren't as many applications and there is always overhead involved in switching operationg systems.

Cost
While free, there are other costs to consider:

• maintenance and support
• upgrading memory and other hardware
• finding people with technical expertise to provide support

How Linux can be used:

Type of box	Use
Server	Host websites and files, can control and secure network traffic
Workstation	Desktops in the buisness environment
Desktop	Focused on home use

*Can also be used for a DNS, Router, Database Server, Software Development, Parallel processing and as a Gateway

Common Linux Distributions (distros):
Red Hat - www.redhat.com
Fedora Core - www.fedora.redhat.com
SuSE - www.novell.com/linux/suse
Debian - www.debian.com
Mandrake - www.mandrakesoft.com


The Linux Shell

The shell interacts with the OS by allowing users to input commands and ensure the kernel executes them.

Commands in this guide are highlighted in blue and italic

Types of Linux Shells:

Shell	Explication
Bash	Default - Has flexibility of C Shell in a Bourne environment. command = bash
Bourne	Original UNIX shell command = sh
C shell	Designed to support C language and provide more inteactive use command = csh
Korn	Combination of C (shell) and Bourne (syntax) command = ksh

Multiple shells can be open simultaneously. You can close the shell with exit or Ctrl-D. You can view open processes including shells using ps.

The command echo $SHELL will show which shell is established at login. (echo prints and follows the commad to the sceen)

The more command is placed in front of a file you wish to view one page at a time.

The head command is similar to more but only displays the first 10 lines of the file. Conversely, the tail command displays only the last 10 lines of a file.

Shell Commands

The command syntax in linux is command -option argument

Linux is case sensitive
Like DOS you can access previous commands with the up and down arrow keys
The Tab key can be used to complete a complex command
Pipes ( | ) allow you to send from one command to the next
; can be used to combine commands

Help and Support
Using man before a command will display a reference manual

Create your own support page by documenting everything you do!

Use system documentation collected in log files. By default logs are stored in the /var/log directory.

The --help command can be used to show a summary, usage and syntax of the command

HOWTOs - Documents describing in detail various aspects of the Linux OS.

HOWTOs can be found in /usr/share/docs and at http://linuxdocs.org/HOWTOs/HOWTO-INDEX/howtos.org

Info Pages can be accessed with the info [topic] command. These documents can be used to access online documentation and printed documentation. An * precceding text indicates that it is linked. Moving the cursor to the text and pressing enter will access the linked info. Other internal info commands include:
U - return to previous document
D - return to the top
Q - exit to command prompt.

LUGs - Linux User Groups

Start and Stop Linux

Init Runlevels
Init reads the /etc/inittabfile to create processes at boot and set the system Runlevel
You can change the Runlevel using telinit

Runlevel options

0 - Halts the System	1 - Single User Mode	2 - Multiuser Mode / without Network File System (NFS)
3 - Full Multiuser Mode	5 - GUI Interface	6 - Reboots System

Shuttng Down
shutdown - warns users and shuts down OS
Shutdown Syntax: shutdown [-t seconds] [-options] time [warning messages]
Switches

Switch	Function
-k	Sends warning but doesn't shut down
-r	Reboot after shutdown
-h	Halt after shutdown
-n	Shutdown without calling init (not recommended)
-f	Skip file system check on reboot
-F	Force file system check on reboot
-c	Cancel shutdown in progress

Booting Up
In Red Hat the default bootloader is LILO below ver 7.1; ver 7.2 and above it's GRUB

Rescue disks can be used as should the kernel become unbootable.
3rd party utilities (e.g., System Commander) can be used as a boot manager