Web Administration

Introduction to Linux

Linux – The Basics

Core component Kernel Kernel along with supporting

function libraries written in C Different software apps modify

appearance but all kernels are common to all distributions

Kernel is directly responsible for controlling the hardware (via device drivers)

Kernel Cont’d

Upgrade kernel Take advantage of new technologies Fix problems

www.kernel.org www.opensource.orgKernel is small – performs faster due to

less code for the processor to analyze.Developed first by Linus Torvalds.

More Sites

www.linuxdoc.org LUG Linux Users Groups (local to

area) www.gnu.org

Linux Basics Cont’d

Package Manager Red Hat RPM’s

Tarball compressed archive of files like zipped files

Linux iso’s downloaded from: www.linuxiso.org

Common Uses

Internet servers File & Print servers Application servers Super computers Scientific / Engineering

workstations Office workstations

Internet Server

Hundreds of network services that provide the framework for an internet server. Mail services Routing FTP services Firewalls & Proxy services Web services News services DNS services

Mail Services

E-mail is distributed via a network of e-mail servers, mail transfer agents (MTA’s). Sendmail, postfix, smail, and qmail.

An MDA (Mail Delivery Agent) downloads from the MTA for the user Procmail, fetchmail

MUA (Mail User Agent) user views e-mail Mutt, pine, printmail, elm, mail, Netscape,

Eudora

Routing

A core service that is necessary for the Internet to function.

Internet a large network of interconnected smaller networks.

Router provides interconnect – it contains information regarding the structure of the Internet sends this info from one network to another.

Linux is a good choice for routers: Linux router Project www.linuxrouter.org

FTP Services

Most common and efficient method for transferring files over Internet.

File Transfer Protocol Keep updated – security issues www.wu-ftpd.org

Firewalls & Proxy Services

Firewalls are placed between network and connection to the internet.

Linux has firewall support built directly into the kernel; utilities ipchains and netfilter/iptables used to configure rules.

netfilter.samba.org

Proxy Services

Requests Internet resources such as URL’s and FTP sites on behalf of the internal computers.

Keep track of the information passed to the client by maintaining a Network Address Translation (NAT) table.

Common linux proxy server is Squid. www.squid-cache.org

Web Services

Internet browser Basic level – web server is just a

server using HTTP provide information.

However – they can process programs CGI/ Perl scripts, PHP scripts

SSL (Secure Socket Layer) is a method for communicating with encrypted material.

www.apache.org

DNS Services

Uniquely identified computers – IP address is assigned. 204.26.82.3

DNS translates URL’s or FQDN such as www.linux.org into an IP address.

BIND (Berkely Internet Name Daemon)

www.isc.org

Typical Install Partitions

/boot -> contains Linux kernel and boot files -> 50MB

/home -> User home dir’s ->200 MB / user/usr -> System commands and utilities -> ~ 2GB/usr/local -> Location of add programs -> ~4GB/opt -> Alternate location of add programs ->

~4GB/var -> Logs and spools -> 2GB/tmp -> Temp files created by programs -> 500MBSwap -> typically twice installed RAM

Filesystem

Linux supports over 50 different filesystems.

ext2 is traditional filesystem used on most Linux systems.

Ext3 and REISER are much more robust as they perform a function called journaling.

A journaling filesystem is one that keeps track of the information written to the hard drive in a journal.

Boot Loader

Is a program started by the BIOS ROM after POST, which loads the Linux kernel into memory.

Can also be used to load other OS’s.

Two types: LILO (LInux LOader) GRUB (GRand Unified Bootloader

Basic Linux Usage

Recall that an OS is merely a collection of software that allows you to use the system hardware in a meaningful fashion.

Kernel in Linux is simply a file called “vmlinux”

There must exist a channel that allows a certain user to communicate with the kernel.

In Linux, called a terminal – allows login access.

Putty – ssh into our box from outside this lab

Shell

Once logged in the basic user interface is a shell – accepts input from user and passes into the kernel for processing.

Default shell – BASH shell (Bourne Again Shell)

It interprets all info the user enters onto the command line.

Commands indicate the name of the program to execute and are case sensitive.

Basic Shell Commands

Options are specific letters that start with a dash “_” appear after the command name and alter the way the command works.

Arguments do not start with a dash. Specify parameters that the command works upon.

Common Commands

clear clears terminal screenreset resets to default terminal settingsFinger displays info on system userswho displays current logged on userswhoami displays your login nameid displays the number associated with

your user acct namedate current date and timecal dispalys calendar for the current

monthexit exits the shell

Help

Linux contains manual pages that help you gather information about any command.

Can be accessed with man “command”

Command for shutdown: shutdown –h now halt reboot