3. introduction of centos

Introduction to Centos

By
Mohd Yasin Abd Karim
yasin@yasin.my

Topics
• Overview
• Using Centos
• Administration
• Networking

Overview
• Is not associated by Red Hat Inc.
• Centos takes freely available Red Hat
Enterprise Linux source code
• A set of packages and ISO images for
installing centos or running it as live CD
• Freely distributed without paying
subscription fees
• Doesn’t achieve 100% compatibility with
RHEL

Stepping Stone to RHEL
• As learning tools to become familiar
• The Backing of a Major Linux Vendor
• Technical Support
• Certified Hardware and Software
• Timely Security patches and Updates
• Certification and Training

Installation
• Media – Centos installation DVD
• PC
– A Pentium class PC ( > 400MHz)
– 128Mb RAM(text), 512MB RAM(GUI)
• Disk Space
– Depending on packages
– 1.5GB to 10GB
• Keyboard & Monitor

Begin Installation
• Insert DVD
• Start your Computer
• Start the Boot Procedure – Press Enter
– Media Check
– Continue
– Choose Language
– Choose keyboard
– Choose Fresh Install

Begin Installation
• Choose your partioning Stratetgy
• Review and Modify partioning and Modify
Partioning Layout
• Configure Boot Loader
• Change Device
• Set Hostname
• Choose a Time Zone

Begin Installation
• Set Root Password
• Install Classes
• Customise categories
• About Install
• Finish Installing

Running Centos Firstboot
• Firewall – allow or deny access
• SELinux – additional layer security
• Date and Time
• Create User
• Sound Card
• Additional CDs
• Get Updates

Getting Started With Desktop
• Checking out Your Home Folder
• Open With
• Side panel
• Background
• Organise your Work – move, delete, rename
• Minimize
• Maximize
• Close

Getting Started With Desktop
• Change Background
• Choose Browser and Others Apps
• Add a Screensaver
• Change the theme
• Configure your Panel
• Workspaces

Using Linux Command
• Shell is command line interpreter
• The shell is powerful, complex

id
• To find out information about your identity,
use the id command as follows:
• $ id
uid=500(timothy) gid=500(timothy)
groups=10(wheel),100(users),500(timothy
)
context=user_u:system_r:unconfined_t

who
• You can see information about your
current login session by using the who
command.
$ who -u -m -H
• NAME LINE TIME IDLE PID COMMENT
• timothy pts/1 2009-04-02 14:12 . 7264
(:0.0)

pwd
• To find out what your current directory is,
type the pwd command:
• $ pwd
• /usr/bin

$HOME
• To find out the name of your home
directory, type the echo command,
followed by the $HOME variable:
• $ echo $HOME
• /home/timothy

cd
• To get back to your home directory, you
can simply type the change directory (cd)
command.
• You can also use the tilde (~) character to
indicate the home directory:
• $ cd ~

ls
• list the contents of your home directory,
using the ls command.
• $ ls -la /home/timothy

ps
• The most common utility for checking
running processes is the ps command.
• $ ps u
• $ ps au
• To see and thereby monitor all the
processes
• $ ps aux | less

Exiting the Shell
• To exit the shell when you are done, type
exit or press [Ctrl]+D.
• There are also administrative commands
in /sbin or /usr/sbin directories.

Getting Help with Shell
• help command
• man command

Linux Filesystems
• /bin —Contains common Linux user
commands, such as ls, sort, date, and
chmod.
• /boot— Has the bootable Linux kernel
and boot loader configuration files
(GRUB).

Linux Filesystems
• /dev—Contains files representing access points
to devices on your systems. These include
terminal devices (tty*), floppy disks (fd*), hard
disks (hd* or sd*), RAM (ram*), and CD-ROM
(cd*). (Applications normally access these
devices directly through the device files, but
end-users rarely access them directly.)
• /etc— Contains administrative configuration
files.
• /home—Contains directories assigned to each
user with a login account.

Linux Filesystems
• /media —Provides a location for mounting devices, such
as remote file systems and removable media (with
directory names of cdrom, floppy, etc.). In CentOS,
many removable media are mounted automatically in
this directory when the media is inserted (CD or DVD) or
connected (USB pen drives or cameras).
• /proc —Provides a mechanism for the kernel to send
information to processes.
• /root—Represents the root user’s home directory.
• /sbin —Contains administrative commands and daemon
processes.

Linux Filesystems
• /sys —A /proc-like file system, added with
the Linux 2.6 kernel and intended to
contain files for getting hardware status
and reflecting the system’s device tree as
it is seen by the kernel. It pulls many of its
functions from /proc.
• /tmp —Contains temporary files used by
applications.

Linux Filesystems
• /usr—Contains user documentation, games,
libraries (lib), and a variety of other user and
administrative commands and files.
• /var—Contains directories of data used by
various applications. In particular, this is where
you would place files that you share as an FTP
server (/var/ftp) or a Web Server (/var/www). It
also contains all system log files (/var/log). In
time, FTP, HTTP, and similar services will move
to the /srv directory to adhere to the Linux
Standards Base (www.freestandards.org/spec).

Creating Files and Directories
• cd— Change to another directory.
• pwd—Print the name of the current
working directory.
• mkdir— Create a directory.
• chmod— Change the permission on a file
or directory.
• ls— List the contents of a directory.

Moving, Copying, and Deleting
Files
• $ mv abc def
• $ mv abc ∼ $ cp abc def
• $ cp abc ∼ $ rm abc
• $ rm *

Using the vi Text Editor
• $ vi /tmp/test

Exploring Other Text Editors
• emacs—Most experienced Linux and UNIX users traditionally have
used vi or emacs as their text editor. Many extensions are available
with emacs to handle editing of many different file types.
• gedit—The GNOME text editor that runs in the GUI
• joe— The joe editor is similar to many PC text editors. Use control
and arrow keys to move around. Press [Ctrl]+C to exit with no save
or [Ctrl]+X to save and exit.
• kate— A nice-looking editor that comes in the kdebase package. It
has lots of bells and whistles, such as highlighting for different types
of programming languages and controls for managing word wrap.
• kedit—A GUI-based text editor that comes with the KDE desktop
• nedit—A good tool for editing source code

Accessing and Running
Applications
• Running yum to Download and Install
RPMs
• # yum install gcc
• Using yum to Install Packages Locally
• yum localinstall /media/disk/CentOS/gftp-*

Using the rpm Command
• The rpm command has the following modes of
operation:
• ■ Install (-i)
• ■ Upgrade (-U)
• ■ Freshen (-F)
• ■ Query (-q)
• ■ Verify (-V)
• ■ Signature check (--checksig)
• ■ Uninstall (-e)
• ■ Rebuild database (--rebuilddb)
• ■ Fix permissions (--setperms)
• ■ Set owners/groups (--setugids)
• ■ Show RC (--showrc)

Linux Applications
• OpenOffice.org
• Firefox
• Thunderbird
• The GIMP (gimp)
• Quanta (html editor)
• GnuCash

Using SSH
• Putty
• winscp

Thank You
• http://www.yasin.my

3. introduction of centos

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