Introduction to Linux
Overview • Linux Overview • Accessing Linux System • Managing User and Group • How Linux Organize Data
Linux Overview • What is Linux • Features and Performance • Linux Distributions • Red Hat Linux Distribution
What is Linux 3 major components of Linux OS : • Kernel • Manage hardware devices • Environment • An Interface for the user • File Structure • Organized the way files are stored on storage device
Features and Performance Technical characteristics of Linux : • Cross-platform • Cost • Power • Availability • Reliability
Linux Distributions • Linux distribution: a package that includes all the softwares needed to install and run Linux • Popular Distribution : • Debian • Fedora Core • Red Hat Enterprise Linux
Red Hat Linux Distribution • Red Hat recognize two different types of clients : • Business Clients • Experimental Clients • Red Hat decided to offer multiple distributions : • "Fedora Core" is freely downloadable version of the distribution • "Red Hat Enterprise" is licensed software
The Fedora Core • Maintained and developed by an Open Source project (Fedora Project) • Release will be issued every 6 months on average • Designed for experimental clients
Red Hat Enterprise Linux • Focus on reliability and stability • Releases issued every 2 years • 3 Enterprise versions • RHE AS • RHE ES • RHE WS • Designed for business clients
Accessing Linux System • Accessing Your Linux System • The Display Manager : GDM • Using Command Line Interface • Logging In and Out • Shutting Down Linux • Starting a GUI from the CLI • Terminal Windows and Pop Up Menu • Mouse Operations • Virtual Desktop
Accessing Your Linux System • The normal procedures are : • Turn on computer • Choose Linux OS in GRUB Boot Loader • Enter user id and password on Login screen using • Command line login prompts • Graphical interface (default)
The Display Manager: GDM • Graphical logins/logout are handled by the GNOME Display Manager • Combination key related with GDM Login window • CTRL-ALT-BACKSPACE • CTRL-ALT-F1 • CTRL-ALT-F7
The Display Manager: GDM (cont…) • 4 pop-up menus at the Login screen • Session • Language • Shutdown • Restart
The Display Manager: GDM (cont…) • 3 choice in GDM Logout window : • Logout • Shutdown • Reboot
Using Command Line Interface • Command line interface facilities • Logging In and Out • Shutting Down Linux • Starting a GUI from the Command Line
Logging In and Out • 2 kinds of prompts in the CLI after login • $ (regular user) • # (root) • To end session use these command • logout, or • exit
Shutting Down Linux • To turn off your computer, shut down Linux first • 2 ways to shut down Linux • halt • Shutdown –h now • To force Linux to reboot • CTRL-ALT-DEL
Starting a GUI from the CLI • 2 related commands to start X Window from CLI # startx or # switchdesk
Terminal Windows and Pop Up Menu • X enables you to open a console session using Terminal window • To access terminal window • right-click on the desktop • select Terminal from the pop-up menu
Mouse Operations • To copy text: Click and drag the mouse across the text to be copied • Text copied automatically into buffer • With some Windows-compatible window manager, press Ctrl-C • To paste text: Click middle mouse button • Or, simultaneously click the left and right buttons
Virtual Desktop • Desktop can be scrollable larger than the size of the monitor using virtual desktop • Use Pager to move around the virtual desktop • Provides a thumbnail view of your virtual desktop
Managing User and Group • User Account • Adding and Removing Users • Adding and Removing Group • The Red Hat User Manager • User Private Groups (UPG)
User Account • 2 kinds of users in Linux • Root • Regular user • For safety, log in as the root user only when performing privileged operations
Adding and Removing Users • useradd • Enter username and user-specific values (e.g. group, user ID) as options on the command line • Get default values from /etc/login.defs • Copies the /etc/skel directory to user’s new home directory • Password is not set • The new user must be given a password using the passwd command
Adding and Removing Users(cont.) • usermod • Takes the same options as useradd • Enables you to change the values for any user features (e.g. group, user ID, etc.) • userdel • Delete the user's login • With the -r option, the user's home directory will also be removed # userdel -r chris
Adding and Removing Group • groupadd • Used to create new groups • Only creates the group category. Users must be added individually • groupdel • Deletes a group • groupmod • Change the name of a group or its ID
The Red Hat User Manager • Add, remove, and modify any user and groups easily with the Red Hat User Manager
User Private Groups (UPG) • Traditionally, all users are assigned into one group named users • With UPG, a new user is assigned into a special group with the same name as the user • E.g., new user dylan is given a default group also called dylan
How Linux Organizes Data • Devices • Filesystems • Directories and Paths • File Permissions
Devices • Linux receives data from, sends data to, and stores data on devices • Generally corresponds to a hardware unit (keyboard, hard disk) • A device may have no hardware counterpart (pseudodevices) • Example • /dev/fd0 • /dev/cdrom • /dev/hda1
Filesystems • Main Task of Filesystem • Organizes the available space • Provides directories and files which is a set of stored data • Every storage device has a filesystem • Common process for new drives • Format • Create Partition • Create File System • Examples: • ext2, ext3, reiserfs, ntfs, vfat, nfs, smbfs
Directories and Paths • Files and directories work as they do under MS-DOS • Users’s current directory after login process is called home directory
Directories and Paths (cont…)
Directories and Paths (cont…) • 2 kinds of pathnames • Absolute • Relative • 2 special directory name • Single dot (.) – current directory • Two dots (..) – parent directory
System Directories • The / is the topmost parent directory • In Windows, we may call it C:\ • 3 Linux system directories : • Program directories where applications are kept • Configuration directories where most configuration files are placed • System log directory that holds the system logs
Program Directories • Program directories are where installed programs usually store their executables • /bin — basic user programs • /sbin — file system management and system operations • /usr/bin — program files designed for user tasks • /usr/sbin — user-related system operation
Configuration Directories • Configuration directories hold most Linux configuration files • /etc – common configuration files • /etc/sysconfig –more specific device & service configuration files
Configuration Files: /etc • /etc holds your system, network, server, and application configuration files • Sample contents: • fstab — a list of file systems • grub.conf — boot systems supported by GRUB
The /usr Directory • Contains subdirectories used to support users • Some important subdirectories: • /usr/bin holds user-accessible applications & utilities • /usr/sbin holds user-accessible administrative utilities • /usr/share directory holds architecture-independent data, including documentation
The /mnt Directory • Contains the mount points for your CD-ROM, DVD, floppy, Zip drives, and other partitions • These are file systems you may be changing frequently • Example : • /mnt/floppy • /mnt/cdrom
The /home Directory • Contains users’ home directories • A subdirectory with same name as user name will automatically be created when a user account is set up • System administrators can access any user’s home directory
The /var Directory • Contains subdirectories for tasks whose files may change frequently • Sample subdirectories: • /var/www — holds Apache web server files • /var/tmp — holds any temporary files programs may need to perform a task
The /proc Directory • /proc is a special file system that is generated in system memory • Does not actually exist on any disk • Its files are interfaces to the kernel • Sample files : • /proc/devices – lists devices currently configured with the kernel • /proc/cpuinfo – holds information about the computer’s CPU processor
The /dev Directory • Contains device files that represents interfaces to actual system devices • Floppy devices (/dev/fd0) • Hard Disk devices (/dev/hda1, /dev/sdb1) • CD-ROM devices (/dev/cdrom) • Other devices • To mount a file system, you have to specify its device name
File Permissions • Restricts access to directories and files based on • The identity of the user • Access modes assigned to each directory and file • 3 kinds of permission
File Permissions (cont…)
Permissions on GNOME • With GNOME you can set permissions graphically
Summary • In this module, you have learned about : • Linux Overview • Accessing Linux System • Managing User and Group • How Linux Organize Data
