Understanding Basic Linux Commands

In Linux, commands are the building blocks for interacting with the system through the terminal. The terminal (or command line) is a powerful tool that allows users to perform tasks efficiently, from simple file management to complex system configurations.

Here’s an overview of some of the most essential basic Linux commands you'll use regularly:

1. Navigating the Filesystem

These commands are used to move around the system's file structure.

• pwd (Print Working Directory):
  Shows the current directory you are in.

  $ pwd
  /home/user
  

• cd (Change Directory):
  Changes the current directory.

  • cd ~ – Takes you to your home directory.
  • cd / – Takes you to the root directory.
  • cd .. – Moves up one directory level.
  • cd - – Takes you to the previous directory.

  $ cd /home/user/Documents
  

• ls (List):
  Lists the contents of the current directory.

  • ls -l – Displays a detailed list (including permissions, owner, file size).
  • ls -a – Lists all files, including hidden files (files starting with a dot).

  $ ls
  $ ls -l
  $ ls -a
  

2. Working with Files and Directories

These commands help you manage files and directories.

• mkdir (Make Directory):
  Creates a new directory.

  $ mkdir new_folder
  

• rmdir (Remove Directory):
  Removes an empty directory.

  $ rmdir empty_folder
  

• rm (Remove):
  Deletes files or directories.

  • rm file.txt – Deletes a file.
  • rm -r folder – Deletes a directory and its contents recursively.
  • rm -f – Forces deletion without prompting for confirmation.

  $ rm file.txt
  $ rm -r folder_name
  

• cp (Copy):
  Copies files or directories.

  • cp source_file destination_file – Copies a file.
  • cp -r source_directory destination_directory – Copies a directory recursively.

  $ cp file.txt copy_file.txt
  $ cp -r folder_name backup_folder
  

• mv (Move/Rename):
  Moves or renames files or directories.

  • mv old_file new_file – Renames a file.
  • mv file.txt /path/to/directory/ – Moves a file to another directory.

  $ mv old_file.txt new_file.txt
  

• touch:
  Creates an empty file or updates the timestamp of an existing file.

  $ touch new_file.txt
  

3. Viewing File Contents

These commands allow you to view the contents of files.

• cat (Concatenate):
  Displays the contents of a file.

  $ cat file.txt
  

• more:
  Displays the contents of a file one page at a time.

  $ more file.txt
  

• less:
  Similar to more but allows both forward and backward navigation.

  $ less file.txt
  

• head:
  Displays the first few lines of a file (default is 10 lines).

  $ head file.txt
  

• tail:
  Displays the last few lines of a file (default is 10 lines).

  $ tail file.txt
  

4. Managing Permissions

These commands are used to manage file and directory permissions.

• chmod (Change Mode):
  Changes the permissions of a file or directory.

  • chmod 755 file – Sets permissions to read, write, execute for the owner, and read-execute for others.
  • chmod +x file – Adds executable permissions.

  $ chmod 755 file.txt
  $ chmod +x script.sh
  

• chown (Change Owner):
  Changes the ownership of a file or directory.

  • chown user:group file – Changes the owner and group of a file.

  $ chown user:group file.txt
  

• chgrp (Change Group):
  Changes the group ownership of a file or directory.

  $ chgrp group_name file.txt
  

5. Searching for Files

These commands help you search for files and text within files.

• find:
  Finds files and directories by criteria such as name, type, or size.

  $ find /home/user -name "*.txt"
  

• grep (Global Regular Expression Print):
  Searches for a pattern within files.

  $ grep "search_term" file.txt
  

• locate:
  Quickly finds files by name (using a prebuilt database).

  $ locate file.txt
  

6. System Information

These commands provide useful system-related information.

• uname:
  Displays system information (kernel version, architecture, etc.).

  • uname -a – Displays detailed information.

  $ uname -a
  

• top:
  Displays real-time system resource usage (CPU, memory, processes).

  $ top
  

• df (Disk Free):
  Displays disk space usage for all mounted file systems.

  $ df -h
  

• du (Disk Usage):
  Displays the disk space used by files and directories.

  $ du -sh /path/to/directory
  

• free:
  Displays memory usage (RAM).

  $ free -h
  

7. Process Management

These commands are used to view and manage running processes.

• ps (Process Status):
  Displays information about running processes.

  • ps aux – Lists all running processes.

  $ ps aux
  

• kill:
  Terminates a process by its PID (process ID).

  $ kill 1234
  

• killall:
  Terminates processes by name.

  $ killall process_name
  

• htop:
  A more advanced and interactive version of top that shows resource usage and allows you to manage processes.

  $ htop
  

8. Networking Commands

These commands allow you to manage and troubleshoot network connections.

• ping:
  Tests network connectivity to a host.

  $ ping google.com
  

• ifconfig (Interface Configuration):
  Displays or configures network interfaces.

  $ ifconfig
  

• ip:
  A more modern tool for managing network interfaces and addresses.

  $ ip addr show
  

• netstat (Network Statistics):
  Displays network connections, routing tables, interface statistics, etc.

  $ netstat -tuln
  

9. Archiving and Compression

These commands allow you to compress and decompress files.

• tar:
  Archives multiple files into a single file.

  • tar -czf archive.tar.gz folder – Compresses a folder into a .tar.gz archive.
  • tar -xzf archive.tar.gz – Extracts a .tar.gz archive.

  $ tar -czf archive.tar.gz folder_name
  $ tar -xzf archive.tar.gz
  

• zip and unzip:
  Compresses files into .zip format and extracts .zip archives.

  $ zip archive.zip file.txt
  $ unzip archive.zip
  

Conclusion

These basic Linux commands form the foundation of your interactions with the Linux operating system. Mastery of these commands will greatly enhance your efficiency and ability to manage and navigate a Linux-based system. Once you become comfortable with these, you can dive into more advanced commands and tasks.