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04.Hidden_Directories.md

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04.Hidden_Directories.md

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Hidden Files and Hidden Directories

In Linux, hidden files and directories are those whose names begin with a dot (.). They are not displayed by default when listing files.

  • To list all files (including hidden files), use: 
    ls -a

File System Navigation Commands

Every directory in Linux implicitly contains two special directories:

  • . represents the current directory.
  • .. represents the parent directory.

Navigation Commands:

  • $ cd .
    Changes to the current directory (rarely used as it has no effect).

  • $ cd ..
    Changes to the parent directory.

  • $ cd
    Changes to the user's home directory (if no argument is passed).

  • $ cd ~
    The tilde ~ represents the user's home directory; this command changes to the home directory.

  • $ cd -
    Changes to the previous working directory.

Example Commands:

# Check current directory
pwd
# List all files, including hidden ones
ls -a
# Navigate up three levels
cd ../../..
# Return to the home directory
cd ~
# Return to the previous directory
cd -

Sample Output:

akshay@Ubuntu:~/Documents/DurgaSoft_Linux/tempdirectory$ pwd
/home/akshay/Documents/DurgaSoft_Linux/tempdirectory
akshay@Ubuntu:~/Documents/DurgaSoft_Linux/tempdirectory$ ls -a
.  ..
akshay@Ubuntu:~/Documents/DurgaSoft_Linux/tempdirectory$ cd ../../..
akshay@Ubuntu:~$ pwd
/home/akshay

Linux File System Hierarchy

The Linux file system is organized as a tree-like structure, starting with the root directory (/). This root directory contains several important subdirectories, each serving a specific purpose:

  1. /bin Directory

    • Contains binary executables related to basic Linux commands.
    • Example commands: ls, touch, mkdir
    which touch  # Output: /usr/bin/touch
which ls     # Output: /usr/bin/ls
which mkdir  # Output: /usr/bin/mkdir

  2. /sbin Directory

    • Contains binary executables for system administration tasks, used primarily by the superuser (root).
    • Example tasks: Disk partitioning, network management.

    Difference between /bin and /sbin:

    • /bin is for commands accessible to all users.
    • /sbin is for commands used by the superuser.

  3. /etc Directory

    • Contains system configuration files that control the behavior of Linux.
    • Important files:
      • /etc/passwd: Contains user information.
      • /etc/group: Contains group information.
      • /etc/hosts: Contains IP and DNS mapping.

Checking File Type

In Ubuntu, directories are often color-coded in blue, while other colors are used for different types of files. However, color conventions vary by distribution, so they are not a reliable method for checking file types.

To check the file type, use:

ls -l

Output Example:

-rw-rw-r-- 1 akshay akshay   342 Aug 29 07:52 directory-hierarchy-linux.mermaid
-rw-rw-r-- 1 akshay akshay   463 Aug 29 07:15 flow-example.mermaid
-rw-rw-r-- 1 akshay akshay    25 Aug 30 14:32 img.durga

The first character in the output indicates the file type:

  • d: Directory
  • -: Normal file
  • l: Link file
  • c: Character special file
  • b: Block special file
  • s: Socket file

Note: c, b, and s represent system files, which are primarily used by the superuser.