Tutorial on Linux Introduction, Installation & Initial Setups

Speaker:

Faran Javed (BIT-5)

Abdul Lateef Khan (BIT-5)

Agenda

Introduction Planning to Install Installing Red Hat Linux Post Installation Configuration First Steps with Linux

Part – IGetting Started

Introduction

For x86 architecture Free implementation of UNIX Used for

Programming Productivity Distributed Computing Telecom & Networking

What is Linux ?

The core kernel of a free operating system first developed and released to the world by Linus Bendict Torvalds in 1991

What’s Red Hat Linux ?

Product of Red Hat Inc. Named after a Cornell university team

hat. Objective:

Develop release and market an easily managed, and easy to use Linux Distribution

Brief History

Initiated by Linux Torvalds Initially the little Clone of Unix Version 0.0.1 was never announced Version 0.0.2 announced October 5

1991 Aim was to build a MINIX look-a-like OS

for AT 386 machines

System Features

complete multitasking, multi-user operating system Complete Implementation of the TCP/IP stack and other

networking software is provided Variety of File systems supported

Ext2 Ext3 XENIX and UNIX System V Microsoft MS-DOS Windows 95 VFAT file systems on a hard drive or floppy. The ISO 9660 CD-ROM file system is also supported.

System Features

The kernel supports demand-paged, loaded executables. Only those segments of a program which are

actually in use are read into memory from disk.

unified memory pool for user programs and disk cache. All free memory is used by the cache, which is

reduced when running large programs.

Executables use dynamically linked, shared libraries

System Features

To facilitate debugging, the kernel generates core dumps for post-mortem analysis.

amount of available memory, Linux also implements disk paging

If several instances of a program are running at once, they share physical memory, which reduces overall usage.

Software Features

Coming Up in Later Slides

Preparing To Install

L inux

Linux Installation

Hardware Compatibility http://hardware.redhat.com/hcl/

Disk Space 400 MB – 5 GB depending on minimal,

personal, server etc. settings

Preparing for the Install Process

Most Common Installation Methods CD-ROM NFS

From a remotely mounted hard drive containing the red hat Linux software

FTP HTTP Hard Drive Partition

Preparing to Install from a CD-ROM

Just make sure System BIOS is set to BOOT from CD_ROM

Partitioning Your Hard Disk Space

If Linux is the only OS than we can auto partition

Assuming a machine with 20 GB Hard Disk & 256 MB RAM

Most basic Scheme Requires a native root partition & a swap partition

Typical Partitions

For a machine with only Linux on the system the scheme will look like: Hard Drive Partition Mount Point Size

/dev/hda1 / 19.14 GB /dev/hda2 swap 512 MB

For a machine already having windows: Hard Drive Partition Mount Point Size

/dev/hda1 /mnt/dos 9.74 GB/dev/hda2 / 8.14 GB

/dev/hda3 swap 512 MB

Hosting Parts of the Linux File System on Partitions /home

Our users home – will contain our personal files, /opt

Directory for additional software packages to be installed

/tmp Used as temporary storage for users

/usr Holds nearly all software on the red hat system

/var Security logs, mails, print spools are under this

directory

Kickstart Installation Method

Automation always saves time Use Red Hats KickStart Configurator A sample ks.cfg file

#System Language

Lang en-US

#Langugae Modules to Install

Langsupport en_US

Sample File

# System Keyboard

keyboard us

# System mouse

Mouse genericps/2

# System time zone

Timezone –utc America/NewYork

# Root password

Rootpw – iscrypted $1$shaldsgfakd3452435gjAJHSGDA/SAD324

The Installation Process Language Selection Keyboard and Mouse configuration Choice of installation type

Personal Desktop If new to the world of Linux

Workstation If you would like a graphical desktop environment, as

well as software development tools Server

If you would like your system to function as a Linux-based server

Custom Greatest flexibility

Upgrade

Installation Process (cont.)

Disk partitioning Automatic Partitioning Manual Partitioning

ext2, ext3, RAID, swap, vfat etc.

Configuring Boot Loader LILO GRUB

Network Configuration Firewall Configuration Language & Time Zone Configuration

Installation Process (cont.)

Authentication setup Package Selection Actual installation Boot Disk creation, VGA and monitor

configuration

First Steps In Linux

Viewing the red hat Linux file system

Ls

Tree

Basic Linux Directories

/ The root Directory /bin Essential Commands /boot Boot Loader Files /dev Device Files /etc System Configuration files /home User home directories /lib Shared libraries /mnt usual mount point /opt Add-on software packages Proc Kernel Information Process control /root Super user /sbin System commands mostly root only /tftpboot Network boot support /tmp temp files /Usr Secondary software file hierarchy /var Variable data (e.g. logos), spooled files

Files in the /etc directory

Fstab FILE SYSTEM TABLE. A text file listing each hard drive, Floppy drive or

other storage attached to your PC. Inittab

The system Initialization table. Defines default run level. Here we can define either to use text or GUI mode.

Modules.conf Contains directions and options used when loading kernel modules to

enable various types of hardware Passwd

The list of users of the system & their accnt info. Printcap

Systems printer capabilities database Shells

A list of approved shells (command line interfaces) Sysconfig

Tree –afx /etc/sysconfig

Interact with the kernel

Use the proc diractory Vi /proc/meminfo Or use the free command /proc/cpu -- cpu family,type & speed /proc/net – important networking info

/proc/net/netstat , /proc/net/route , /proc/net/dev

/proc/version – kernel version

Remote Login

Use SSH – secure shell Linux also supports :

Telnet Rlogin

Changing user Information

Chfn – change finger information Finger – get finger information

Accessing Documentation

Apropos partition Will display related commands

Using the Man pages

Man rm Will display manual pages for the rm

command

Grep

Grep alateef /etc/passwd This will search for alateef in /etc/passwd

Whereis fdisk

Using Environment Variables

PWD – current directory USER – declare user name LANG – To set language defaults SHELL – TO declare the name and location of the

current shell PATH – set default location of executable files LD_LIBRARY_PATH – location of important software

libraries TERM – set the type of terminal in use MACHINE – declare system type, architecture & so on

$env /etc/profile

Navigating & searching with shell Cd /home/….. Cd .. Whereis Locate Apropos Cat <filename>– contents of file Less <filename> - allows scrolling while reading contents of file

name Mv <file1> <file2> Mv <file> <dir> Cp <src> <dst> Rm <file> Rmdir <dir> Grep <string> <file>

Compressing & Decompressing Files

Bunzip2 - expands a compressed file Bzip2 – compresses or expands files &

directories Gunzip Gzip Shar Tar unshar

Using Text Editors

Ed Emacs Jed Joe Mcedit Pico Sed Vim Vi

Gedit Kate Kedit Nedit kwrite

Working with vi

H,j,k,l – cursor movement Delete character – x Delete line – dd Mode toggle – ESC, Insert (or i) Quit - :q Quit without saving - :q! Save file - :w Text search - / Run a shell command - :sh (use exit to return)

Mounting a Drive

Compiling a simple C Program

Internet Configuration

Ethernet Configuration Things you should know

IP address If you're configuring loopback mode, it is 127.0.0.1

Subnet mask It is always 255.0.0.0 for loopback address

Broadcast address It is equal to your subnet address with 255

replaced as the host address IP address of Gateway IP address of Name server

Configuration using system scripts Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=staticIPADDR=192.168.8.139NETMASK=255.255.255.0BROADCAST=192.168.8.255GATEWAY=192.168.8.1

Edit the file /etc/sysconfig/networkNETWORKING=yes HOSTNAME=linux.niit.edu.pk GATEWAY=192.168.8.1

Configuration of Static IP via command line

The shell provides two programs for NIC configuration, ifconfig & route ifconfig

For configuring the network device interface with certain parameters, such as the IP address, subnetwork mask etc.

Remember to bring the interface down & up when modifying Set IP Address

ifconfig lo 127.0.0.1ifconfig eth0 192.168.75.20 netmask 255.255.255.0

Verify Settingsifconfig eth0

route To show and manipulate the IP routing table Add default gateway

route add default gw 192.168.1.254route add –net 192.156.79.0 netmask 255.255.255.0 dev eth0

Important Configuration files

/etc/hosts Contains a list of IP addresses and the hostnames they

correspond to127.0.0.1 ENT localhost.localdomain

localhost

/etc/networks lists the names and addresses of your own and other

networks Used by the route command and allows you to specify a

network by name instead of by addressdefault 0.0.0.0 # default route - mandatory

loopnet 127.0.0.0 # loopback network - mandatory

niit-net 202.83.166.171 # Modify for your own network address

Important Configuration files

/etc/host.conf Specifies how your system resolves hostnames

order hosts,bind /etc/resolv.conf

Configures the name resolver specifies the address of your nameserver (if any) domains that you want to search by default if a

specified hostname is not a fully specified hostname

domain niit.edu.pk

nameserver 10.10.10.1

Network Configuration for DHCP Edit the file /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=dhcpIPADDR=NETMASK=BROADCAST=GATEWAY=

Edit the file /etc/sysconfig/networkNETWORKING=yes HOSTNAME=GATEWAY=

Basic PPP Configuration for Modems In Windows, modems and other serial devices are named

COM1, COM2 etc. In Linux, these are referred as /dev/ttyS0, /dev/ttyS1

At installation time a symbolic link called /dev/modem will be created for the modem

KDE graphical tool called “kppp” configures a dialup connection easily

Located in /usr/bin/kppp Red Hat requires the root password to be entered each

time kppp is executed for security reasons Some distributions allow any user to execute this

program such as SuSE

Configuring kppp

Start kppp

Click the Setup button and then click the Device Tab

In the Model tab, click Query Modem, it should come up with some results

Setting up your ISP Info Accounts button

You might need to add the line route add default ppp0 to the field Execute program upon connect: to ensure the default gateway is set to the default gateway from your ISP.

Enter your username and password for your ISP and Connect

Users Groups & Permissions

User Accounts

Personal Accounts AAA (Authentication, Authorization,

Accounting) Administrative Accounts

root Accessed using the su command

Daemon accounts e.g., news daemon

The passwd File Every account on the system has an entry in the file /etc/passwd

username:password:uid:gid:gecos:homedir:shell Username

A unique character string, identifying the account Password

An encrypted representation of the user's password UID

unique integer the system uses to identify the account GID

an integer referring to the user's default group, found in the file /etc/group

gecos Misc. information like user's real name, office address or

phone no. etc.

The passwd File

homedir user's home directory

shell name of the program to run when the user logs in e.g.,

/bin/bash or /bin/tcsh

root:ZxPsI9ZjiVd9Y:0:0:The root of all evil:/root:/bin/bash

Shadow Passwords

Encrypted passwords in /etc/passwd are potential security risk

Instead /etc/shadow is used Contains the real encrypted passwords Readable only by root Contain similar fields but empty or bogus values

passwd command -n : sets the minimum number of days between

changes -x : the maximum number of days between changes -w : the number of days a warning is issued before a

password expires -i the number of days of inactivity between the expiry

of a password and the time the account is locked

The Group File To logically organize sets of user accounts To allow users to share files within their group or groups Every user is assigned to at least one group The file /etc/group contains a one-line entry for each group on the

systemgroupname:password:gid:members

password is an optional encrypted password associated with the group, which allows users not in this group to access the group with the newgrp command

members is a comma-separated list of usernames identifying those users who are members of this group but who have a different gid in /etc/passwd

root:*:0: bin:*:1:root,daemon users:*:50: bozo:*:51:linus,mdw megabozo:*:52:kibo

Creating Accounts

Adding an entry to /etc/passwd Creating the user's home directory Setting up the user's default

configuration files

adduser or useradd

Deleting and Disabling Accounts To delete an account

remove the user's entry in /etc/passwd remove any references to the user in /etc/group delete the user's home directory any additional files created or owned by the user

userdel -r lateef Disabling a user account

add an asterisk to the first character of the password field of the /etc/passwd entry

kashif:*BjDf5hBysDsii:104:50:lateef Rao:/home/aclark:/bin/bash

Modifying User Accounts

Simply edit /etc/passwd and /etc/group To change a user's password, use the

passwd command Use chown command to change

ownership of files chown -R alateef

/home/alateef

File Ownership and Permissions Permissions refer to the ways in which

someone can use a file or directory For files

Read permission means you can look at the file's contents

Write permission means you can change or delete the file

Execute permission means you can run the file as a program

For directories Read permission means you can list the contents

of that directory Write permission means you can add or remove

files in that directory Execute permission means you can list

information about the files in that directory Who gets these permissions?

Linux has three levels of permissions Owner Group Other

File Ownership and Permissions

Owners and Groups

Each file has an owner and a group

Changing the Owner, Group

Common mistake when creating a directory under /home for a new user as root

chown command changes the owner of a file only root can use chown for changing ownership of a

file chgrp command changes the group

any user can change the group to another group to which he belongs

# chown root /home/lateef/apache.conf # chgrp bin /home/lateef/apache.conf

# chown root.bin /home/lateef/apache.conf

Changing the Permissions

The permissions are also called the file's "mode" The command that changes permissions is chmod Symbolic Mode

$ chmod +x header.c

$ chmod u-x header.c

$ chmod ug+rwx header.c

User permission is u, group permission is g, and other is o

Changing the Permissions Absolute Mode

in terms of bits and octal notation

$ chmod 400 header.c $ chmod 555 header.c

To set the default mode that is assigned to each file you create umask command

$ umask 027

Shutting down the machine

Shutdown –h now Or shutdown –h 0 Shutdown –h 18:30 “system is going

down for maintenance”

Shutdown –r now shutdown –r 0

References

http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/install-guide/

Red Hat Linux 9 Unleashed – Bill Ball & Hoyt Duff