Basic Linux Commands

1. 1. ls - List Files and Directories:

   • This command is used to list the files and directories in the current working directory.
   • Example: ls
   • Following are some frequently used options in Linux ls commands: Options Description ls -a list all files including hidden file starting with '.'. ls -d list directories - with ' */'. ls -l list with long format - show permissions. ls -F Append indicator (one of */=>@|) to entries. ls -lh This command will show you the file sizes in human readable format. ls -r list in reverse order. ls -i list file's inode(index) number. ls -ltr View Reverse Output Order by Date. ls -t sort by time & date. ls -n It is used to print group ID and owner ID instead of their names. ls -m A list of entries separated by commas should fill the width. ls -g This allows you to exclude the owner and group information columns. ls -q Force printing of non-graphic characters in file names as the character `?';. ls -Q Place double quotations around the entry names.
   


2. 2. touch - Create Empty File:

   • The touch command creates an empty file or updates the timestamp of an existing file.
   • Example: touch sample.txt

3. 3. vi - Text Editor:

   • The vi command is a text editor that allows you to create, edit, and manipulate text files. It operates in different modes: command mode and insert mode.
     • To open a file for editing: vi filename
     • Example: vi sample.txt
     • Switch between modes: Press i for insert mode, and Esc for command mode.
     • Basic navigation: Arrow keys, h, j, k, l.
     • Editing text: x (delete character), dd (delete line), yy (copy line), p (paste).
     • Save and exit: :w (save), :wq (save and exit), :q! (exit without saving).
     • Search text: Press /, type search term, and press Enter. To find the next occurrence, press n.
     • Replace text: :s/old/new/g (replace all occurrences of "old" with "new").
     • Undo and redo: u (undo), Ctrl + r (redo).

4. 4. cat - Concatenate and Display File Content:

   • Displays the content of a file.
   • Example: cat sample.txt

5. 5. mkdir - Make Directory:

   • Creates a new directory.
   • Example: mkdir new_directory

6. 1. 6. mv - Move or Rename Files or Directories:

      • Moves files or directories to a new location or renames them.
      • Example: mv file.txt new_location/ or mv old_name.txt new_name.txt
   2. 7. cd - Change Directory:
7. • Allows to change thecurrent working directory.
   • Example: cd /path/to/directory

8. 8. cp - Copy Files or Directories:

   • Copies files or directories from one location to another.
   • Example: cp file.txt /path/to/destination

9. 9. date - output the current date and time in the default format.

   • Example: Thu Dec 16 12:34:56 UTC 2023

   10. rm - Remove Files or Directories:

10. • Deletes files or directories.
    • Example:rm smaple.txt (remove a file),
    • rm -r directory/ (remove a directory and its contents)

11. 11. cd ../ - One step back in directory:

    • Example: cd ../ - Go to the the previous folder

12. 1. 12. ps - Display Information about Running Processes:

       • Shows information about currently running processes.
       • Example: ps aux
       • The aux options display a detailed list of all processes, including those of other users. This is one of the most commonly used options.

13. 13. cat /proc/cpuinfo:

14. Displays the System CPU information.

15. 14. df - Display Disk Space Usage:
1. Shows information about disk space usage.
2. Example: df -h
16. 15. sudo yum install package_name:
17. sudo: This is a command that allows a permitted user to execute a command as the superuser (root) or another user, as specified by the security policy.

1. • yum: This is the package management tool used on Red Hat-based systems for installing, updating, and removing software packages.
   • install: This is the action you want yum to perform, indicating that you want to install a package.

2. 16. pwd - Print Working Directory:

   • Displays the current working directory, showing the full path.
   • Example: pwd

3. 17. chmod - Change File Permissions:

   • Modifies the permissions (read, write, execute) of a file.
   • Example: chmod +x script.sh (adds execute permission to "script.sh")

4. 18. chown - Change File Owner:

   • Changes the owner and/or group of a file.
   • Example: chown user:group file.txt

5. 19. kill - Terminate a Process:

6. • Terminates a running process by sending a signal.
   • Example: kill process_id

7. 20. man - Display Manual Pages:

   • Displays the manual pages for a specific command, providing detailed information.
   • Example: man ls