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Introduction to Linux

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

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Introduction to Linux

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  1. Introduction to Linux

  2. Overview • Linux Overview • Accessing Linux System • Managing User and Group • How Linux Organize Data

  3. Linux Overview • What is Linux • Features and Performance • Linux Distributions • Red Hat Linux Distribution

  4. 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

  5. Features and Performance Technical characteristics of Linux : • Cross-platform • Cost • Power • Availability • Reliability

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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)

  12. 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

  13. The Display Manager: GDM (cont…) • 4 pop-up menus at the Login screen • Session • Language • Shutdown • Restart

  14. The Display Manager: GDM (cont…) • 3 choice in GDM Logout window : • Logout • Shutdown • Reboot

  15. Using Command Line Interface • Command line interface facilities • Logging In and Out • Shutting Down Linux • Starting a GUI from the Command Line

  16. 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

  17. 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

  18. Starting a GUI from the CLI • 2 related commands to start X Window from CLI # startx or # switchdesk

  19. 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

  20. 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

  21. 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

  22. Managing User and Group • User Account • Adding and Removing Users • Adding and Removing Group • The Red Hat User Manager • User Private Groups (UPG)

  23. User Account • 2 kinds of users in Linux • Root • Regular user • For safety, log in as the root user only when performing privileged operations

  24. 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

  25. 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

  26. 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

  27. The Red Hat User Manager • Add, remove, and modify any user and groups easily with the Red Hat User Manager

  28. 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

  29. How Linux Organizes Data • Devices • Filesystems • Directories and Paths • File Permissions

  30. 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

  31. 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

  32. Directories and Paths • Files and directories work as they do under MS-DOS • Users’s current directory after login process is called home directory

  33. Directories and Paths (cont…)

  34. Directories and Paths (cont…) • 2 kinds of pathnames • Absolute • Relative • 2 special directory name • Single dot (.) – current directory • Two dots (..) – parent directory

  35. 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

  36. 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

  37. Configuration Directories • Configuration directories hold most Linux configuration files • /etc – common configuration files • /etc/sysconfig –more specific device & service configuration files

  38. 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

  39. 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

  40. 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

  41. 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

  42. 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

  43. 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

  44. 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

  45. 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

  46. File Permissions (cont…)

  47. Permissions on GNOME • With GNOME you can set permissions graphically

  48. Summary • In this module, you have learned about : • Linux Overview • Accessing Linux System • Managing User and Group • How Linux Organize Data

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