1. Red Hat ® I NTERNET S YS A DMIN 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

18. 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

19.  2 related commands to start X Window from CLI # startx or # switchdesk Starting a GUI from the CLI

20. 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

21. 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

22. 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

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

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

25. 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

27. 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

28. 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

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

30. 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

31. How Linux Organizes Data  Devices  Filesystems  Directories and Paths  File Permissions

32. 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

35. 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

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

38. Directories and Paths (cont…)

39.  2 kinds of pathnames Absolute Relative  2 special directory name Single dot (.) – current directory Two dots (..) – parent directory

40. 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

41. 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

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

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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

51. 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

52. File Permissions ( cont… )

53. Permissions on GNOME  With GNOME you can set permissions graphically

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