Overview of Linux

Linux File system Hierarchy

  • What are file systems?
    • Data structure and behavior that an operating system implements to keep track of files on a disk or partition to organize of files and directories [1].
    • Before a disk can be used, it should be formatted with certain file system, which initialized data structures need to be written to the disk.
    • Unlike Windows file system (NTFS/FAT), there is only one root in the file system hierarchy of many Unix clones i.e. /, known as root.
    • Unlike in Windows, Unix system don’t have the concept of Drives (e.g. C: or D:), so each partition in physical hard disk should be associated or linked with some directories, also know as mounting file system.
    • In unix Every think is a file or process. So device can also be represented with file located in /dev directory.
  • Directories in Root (/)
  • /bin: Essential Command binaries like cp, mv
  • /boot: contains files related to boot loader
  • /dev: Contains device files
  • /lib: Essential shared libraries and kernel modules
  • /media: mount point for removable media
  • /mnt: Mount point for mounting a file system temporarily
  • /opt: Add-on application software packages
  • /sbin: Essential system binaries
  • /srv Data for services provided by the system (usually found in Suse and Debian system)
  • /tmp: temporary files
  • /usr secondary hierarchy, most of the application programs are installed in /usr directories
  • /var: variable data.
  • /proc: virtual files system, which is used to store kernel parameter files temporarily
  • Accessing into Linux System
    • Two type of logins:
      • Virtual Consoles (6 text base terminals available)
      • Graphical logins (1 GUI Display manager)
    • Requires user name and password (root is a super user or administrator)
    • Each user has a home directory
    • Switching Terminal:
      • Press “Alt+F1 to F6” to access Text mode or virtual terminal in most Linux system.
      • Press “Ctrl+Alt+ F1 to F6” from GUI mode to access virtual terminal.
      • Press “Alt+F7” to access GUI, (in some Linux system like Fedora, “Alt+F1” will switch to GUI mode. Alternatively, starx command can be typed in console to access GUI screen or “init 5” can be executed in console.
    • Switching between users
    • A user can switch to another by typing ‘su – <username>’, where – option will reset the OS environment as per setting for switched user <username>. For example, “su – shiba” will switched to user name shiba. However, switching to root user don’t require to provide user’s name (i.e. “su -”).
  • Note: in Lab environment where students don’t have their own Linux system can access Linux Virtual Machine with SSH clients like Putty, Xshell and SecureShell etc. for following Lab exercises.
  • What is shell
    • Shell is a interactive user interface between the user and the kernel to execute program or application in an OS. BASH is one of the most popular shell available in Linux/Unix system.
  • Starting with shell
    • pwd: prints name of current working directory.
    • ls: list files in current directory.
  • Using help
    • man <command_name>: provides detail manual of particular command (e.g. #man ls)
    • <command_name> –help : provides brief command options and parameters. (e.g. #ls –help). Most of the unix command also accesp -h option for help, but in some commands like in ls command. In some commands like ls and du, -h options is provided for human readable content display.
    • Info <command_name>: it is an alternative help line for man and –help option.
    • Documentation: most of the document available with application are stored in /usr/share/doc directory


  • Linux command and configurations based on RHCE certification:
  • Linux Note 1 Linux Note 2 Linux Note 3 Linux Note 4 Linux Note 5 Linux Note 6 Linux Note 7


  •  Source [1]: http://www.tldp.org/LDP/Linux-Filesystem-Hierarchy/html/c23.html

  • Source [2]: RH033 Red Hat Linux Essentials.


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