Introduction to Centos By Mohd Yasin Abd Karim firstname.lastname@example.org
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:• $ iduid=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.
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