1. The UNIX File System

2. File System Definition
A file system is a hierarchy of directories, subdirectories, and files that organize and manage the information on hard disks.

3. Directories
Directories are created so users and applications can easily find files.
Without directories, all files would be in the same location with no organization to them.
Similar to using the backseat of your car to hold homework assignments and papers.

4. Hierarchical Directory Structure
Directories are organized in an ‘upside-down’ tree fashion.
The root is at the top.
Directories may contain other directories and files.
Analogous to file drawers and file folders

5. Directories
The root directory is often represented as / (the forward slash symbol).
Parent directories contain other directories (called children).
Child directories are located within other directories (called parent directories).

6. Path Names Each file can be represented by its path name.
The path name simply represents the file’s location in the file system.
Example: /home/user2/dir1/coffees/beans

7. Path Components
Directory paths allow users to navigate within the file system.
Slashes within the path name are delimiters between object names.
Object names can be directories, subdirectories or files
DOS and Windows uses a backward slash (\) to separate directories. UNIX and Linux use a forward slash (/).
A slash (/) in the first position of any path name represents the root directory.

8. Exploring the Root File System
The root directory contains sub-directories that contain files:
/bin contains binaries, or executables needed to start the system and perform system tasks available to all users
/boot contains files needed by the bootstrap loader as well as kernel images
/dev contains system device reference files
Continued…

9. Exploring the Root File System
Root subdirectories continued:
/etc contains configuration files that the system uses when the computer starts
/lib contains kernel modules, security information, and the shared library images
/mnt contains mount points for temporary mounts by the system administrator
/proc is a virtual file system allocated in memory only; it tracks the running processes on the system
Continued…

10. Exploring the Root File System
Root subdirectories continued:
/root is the home directory of the root user, or the system administrator
/sbin contains essential network programs used only by the system administrator
/tmp is a temporary place to store data during processing cycles
/var contains subdirectories which have sizes that often change, such as error logs, print jobs, and incoming

11. Absolute Path Names
An absolute path name specifies a file or directory in relation to the entire UNIX file hierarchy.
directory s

12. Relative Path Names
A relative path name describes the location of a file or directory as it relates to the current directory.
directory

13. Path Name Types Comparison
If the path name starts with /:
It is an absolute path name.
Ex: /etc/resolv.conf
If the path does not start with /:
It is a relative path name.
Ex: user01/file1
Absolute path names specify the exact location of a file or directory.
In Windows: C:\Windows\System32\file.dll
Relative path names specify where a file or directory is in relation to the current spot in the file system.
In the Windows folder: System32\file.dll

14. Useful File System Commands
pwd (print working directory)
Displays current directory location
cd (change directory)
Change to a specified directory
ls (list)
Display contents of directory

15. cd (by itself) places user in home directory
Using cd
cd /home
Absolute Path
In /home, cd user01/dir1
Relative Path
cd (by itself) places user in home directory

16. cd Shortcuts
cd ..
Moves the user up one directory to the parent directory
cd ../tmp
cd .
Keeps the user in the current directory
cd ./coffees
cd ~
Moves the user to the home directory
cd ~/file1

17. ls displays the directory contents.
The ls Command
ls displays the directory contents.
ls can be used by itself to list the contents of the current directory.
ls can be used with a directory path to display the contents of that directory. ls
ls /home

18. The ls –a Command
Use ls –a to list all files and directories, including hidden files, . and .. directories.

19. The ls –l Command
Use ls –l to display long directory listings.

20. The * and ? are also referred to as wildcard characters.
Metacharacters
Metacharacter are characters that have special meanings to UNIX and Linux commands.
Examples:
*, <, >, | (pipe), !, [, ], ? and others
The * and ? are also referred to as wildcard characters.

21. The * Wildcard
* is used to represent one or more characters

22. The ? Wildcard
? is used to represent one character

23. The [ ] Metacharacters
Using [ ], anything inside the brackets will be matched

24. The ; Metacharacter
; is used to separate multiple commands on one line