RH030 Linux Computing Essentials

1. RH030 Linux Computing Essentials Understanding the Basic Linux Structure

2. Objectives • Structure of the Linux OS • Use of shells and their relationship to C.L • Use of the system directories • FSH = hierarchical filesystem structure • FSH = structure of the directory tree structure • Navigation using absolute / relative pathnames • Structure of the command line. • Basic navigation commands Linux+ Guide to Linux Certification, 2e

3. Linux / UNIX - Interfaces User Applications User mode Desktop– GNOME, KDE XWindows – intel = xfree86 SHELL – Command line Interface Standard Utility Programs - Kernel - Standard library Programs Kernel mode Hardware Linux+ Guide to Linux Certification, 2e

4. Applications XWindows shells Kernel Hardware Main Elements of Linux/Unix OS • Kernelmanages memory manages system resources manages processes schedules programs manages file system - data/file access and storage - enforces security mechanismsperforms all hardware access Linux+ Guide to Linux Certification, 2e

5. Applications XWindows shells Kernel Hardware Main Elements of Linux/Unix OS • ShellThere are many different shell programs: - Bourne (sh), Korn (ksh), C (csh) Bourne Again (bash) It acts as the interface between the user and the kernel presents each user with a command promptinterprets commands typed by a userexecutes user commandssupports a custom environment for each user • Utilitiesfile management -rm, cat, ls, rmdir, mkdiruser management - passwd, chmod, chgrpprocess management - kill, pscompression – tar, cpio, gzipadministrative – useradd, groupadd, who, su Linux+ Guide to Linux Certification, 2e

6. Difference between the Windows & Linux Directory Structure Figure 4-1: The Windows filesystem structure Figure 4-2: The Linux filesystem structure Linux+ Guide to Linux Certification, 2e

7. Linux FSH = Directory Tree Structure Linux+ Guide to Linux Certification, 2e

8. Under the \ are the System Directories Table 5-1: Linux directories defined by FHS Linux+ Guide to Linux Certification, 2e

9. 2 Types of Unix/Linux users Superuser # = There is only one system administrator account, created during installation They always log onto the system as root. Regular User $= These are created by the superuser • All accounts have a home directory. • The hierarchical filesystem starts from the top of the tree “ /” which is called the “root” directory . • Immediately under which are the system directories. • 2 of these are: • /root directory which is the home directory for the superuser /home directory which contains a separate home directory for each of the regular user accounts.

10. You have to Login to Linux • Multiuser environments require you to have a users account. • You can log in thru command-line interface or a GUI interface. • The Command-line interface is always available. • You need to install the GUI interface during installation to use it. • Login will also require a password. Linux+ Guide to Linux Certification, 2e

11. Even after you login Linux still offers the user many choices for their Interfaces 1. Command-line using shell • There are multiple CL screens available for the use of the user. • You access them by using the Crtl+Alt+F key combinations to change to separate terminal screens. 2. Graphical Interface using Xwindows • You can start a GUI interface on any of these multiple screens . • You can access a GUI interface with the Crtl+Alt+F7 key combination • You can use the Crtl+Alt+Bkspace key to shutdown the GUI • You can have access to both GUI & CL interfaces. • Load the GUI by default and use terminal program for CL • Or load CL by default and switch to a GUI by typing startx • This will start a GUI environment on top of the shell Linux+ Guide to Linux Certification, 2e

12. Linux has a wonderful GUI environment. • But we will not spend much time on the GUI. • Because anyone can easily learn to use a GUI. • CL is much harder. • And to be a Linux system administrators you use command-line. • The Linux certifications all focus on command-line. Linux+ Guide to Linux Certification, 2e

13. / FSH = Directory Tree Structure • FSH is just an inverted tree of containers & files • parent directories & child directories (subdirectories) • top the tree is always designated as a forward slash (/) • this is called the root directory Linux+ Guide to Linux Certification, 2e

14. FSH uses pathnames to access items • A pathname specifies the location of a file on disk. • Every file and directory on a system has a pathname. • The ‘/’ separates file and directory names in a pathname. • What is the pathname of the file pointed to by the red arrows? Linux+ Guide to Linux Certification, 2e

15. Pathname Components • Directory paths are important you navigate within the system using them. • Slashes within the pathname are delimiters between object names • Object names can be either sub-directories or files Linux+ Guide to Linux Certification, 2e

16. 2 Types of Pathnames • Absolute Pathname • Specifies the location of a file in relation to the entire file system. • Starts with the root (‘/’) directory. • Use the pwd (“Print Working Directory”) command to get the absolute pathname to the current directory. • Relative Pathname • Does not start with ‘/’. • Specifies the location of a file in relation to the current directory. • Can get to a file or directory in the current directory by simply using its name. Linux+ Guide to Linux Certification, 2e

17. Changing Location in the FSH • You use the cd(“Change Directory”) command to move to a different directory in the file system. • Accepts either absolute or relative pathnames. • Relative pathname symbols • Are used for navigational shortcuts /timesavers. • . (dot) The current directory. • .. (dot dot) The parent directory. • ~ Refers to your home directory Linux+ Guide to Linux Certification, 2e

18. Absolute verse Relative pathnames • Absolute pathname: always start from the top with a / cd /home/sheila/class-files/dir1 • Relative pathname:never starts with “/” cd class-files/dir1 cd ./class-files/dir1 cd ~/class-files/dir1 • Relative pathnames can also move up: • using a “..” per layer cd ../class-files/dir1 cd ../../../ class-files/dir1

19. Examples of Absolute Pathnames Absolute pathname to the user2 directory = /home/user2 Absolute pathname to the dir1 directory = /home/user2/dir1 Absolute pathname to the coffees directory = /home/user2/dir1/coffees Linux+ Guide to Linux Certification, 2e

20. Examples of Relative Pathnames If your current directory is /home: Relative pathname to the user2 directory = user2 Relative pathname to the dir1 directory = user2/dir1 Relative pathname to the coffees directory = user2/dir1/coffees Linux+ Guide to Linux Certification, 2e

21. Basic Structure of Command Syntax • Before you can use Unix commands effectively, you need to understand their general syntax. • $ command [option(s)][argument(s)] Shell Prompt Command Modifiers Executable Name Command Targets Linux+ Guide to Linux Certification, 2e

22. Example of command syntax <command> <options> <arguments> • First immediately after the prompt is the command $ ls • Commands are case sensitive and mostly in lowercase • A command may or may not have options • Options are used to modify the output. $ ls - l • A command may or may not have arguments • Arguments are usually files or directories $ ls - al /etc

23. Example of Basic Shell Commands • Linux Commands are case sensitive DOS LINUX PURPOSE cd cd change directory dir ls list the directory contents copy cp copy move mv move del rm delete/remove deltree rm -r remove directory + contents type cat display a file copy con cat > create a file md mkdir create a new directory rm rmdir delete a directory

24. Command Line Syntax • refers to the structure of the command • specifies allowable options and arguments Linux+ Guide to Linux Certification, 2e

25. Command Line Examples Linux+ Guide to Linux Certification, 2e

26. Command-Line Syntax Rules Linux+ Guide to Linux Certification, 2e

27. Viewing the contents of Directories • lscommand: • ls on it’s own display’s a brief listing of the contents of the directory – listing the items names only • Most commonly used options: • ls – l : detailed display or long listing of items. ll command: Is the default Alias for ls -l • ls – a : displays hidden files Linux+ Guide to Linux Certification, 2e

28. Viewing the contents of files • catcommand: cat dante displays dante in the cwd cat ./dante displays dante in the cwd cat ~/dante displays dante in your home directory • It can actually be used in many ways. • Which we will see later. Linux+ Guide to Linux Certification, 2e

29. Some really basic commands • Where am I in the FSH $ pwd • Moving around the FSH $ cd /etc $ cd thesis/fig $ cd .. • Displaying the contents of directories. $ ls $ ls -a $ ls -l $ ls -al $ ls -ald

30. Do you have a Redhat Academy Account yet? • Because from now on - you will need one! • Lets do todays’s exercises