1. cd - Change directory

    cd /home/user/Documents - changes the current directory to /home/user/Documents.

  2. ls - List directory contents

    ls - lists the contents of the current directory.

    ls /home/user/Documents - lists the contents of the directory /home/user/Documents.

  3. pwd - Print working directory

    pwd - prints the current working directory.

  4. mkdir - Make directory

    mkdir new_directory - creates a new directory named new_directory.

  5. rmdir - Remove directory

    rmdir old_directory - removes the directory named old_directory if it’s empty.

  6. touch - Create a file

    touch new_file.txt - creates a new file named new_file.txt.

  7. cat - Concatenate and print files

    cat file.txt - prints the contents of file.txt to the terminal.

  8. cp - Copy files or directories

    cp file.txt /home/user/Documents - copies file.txt to the directory /home/user/Documents.

  9. mv - Move or rename files or directories

    mv file.txt new_file.txt - renames file.txt to new_file.txt.

    mv file.txt /home/user/Documents - moves file.txt to the directory /home/user/Documents.

  10. rm - Remove files or directories

    rm file.txt - removes file.txt from the current directory.

    rm -r directory - removes directory and all its contents recursively.

  11. chmod - Change file permissions

    chmod 755 file.txt - sets the file permission for file.txt to read, write, and execute for the owner, and read and execute for others.

  12. chown - Change file ownership

    sudo chown user:group file.txt - changes the ownership of file.txt to user and the group to group.

  13. ps - Show current processes

    ps - displays a list of the current processes running in the terminal.

  14. top - Show system processes and resource usage

    top - displays a dynamic real-time view of the processes currently running in the system.

  15. kill - Send a signal to terminate a process

    kill process_id - terminates the process with the specified process_id.

  16. sudo - Run a command with elevated privileges

    sudo apt-get update - runs the command apt-get update with elevated privileges.

  17. su - Switch to another user account

    su - user - switches to the user account named user.

  18. ping - Check network connectivity

    ping google.com - sends a ping request to google.com to check network connectivity.

  19. traceroute - Trace the route taken by packets through an IP network

    traceroute google.com - displays the route taken by packets through the IP network to reach google.com.

  20. ifconfig - Show network interface configuration

    ifconfig - displays the configuration details of all the network interfaces in the system.

  21. netstat - Show network status

    netstat - displays the current network connections and their status.

  22. iptables - Configure firewall rules

    iptables -L - lists all the current firewall rules.

  23. wget - Download files from the web

    wget http://example.com/file.zip - downloads the file file.zip from the web.

  24. curl - Transfer data from or to a server

    curl http://example.com/api - sends an HTTP GET request to example.com/api and displays the server’s response.

  25. ssh - Connect to a remote server securely

    ssh user@remote_server - connects to remote_server as user.

  26. scp - Securely copy files between hosts

    scp file.txt user@remote_server:/home/user - copies file.txt to remote_server’s /home/user directory.

  27. tar - Archive files and directories
    • tar -cvf archive.tar file.txt - creates a new tar archive archive.tar containing file.txt.
  28. gzip - Compress files
    • gzip file.txt - compresses file.txt and renames it to file.txt.gz.
  29. unzip - Extract files from a ZIP archive
    • unzip archive.zip - extracts all the files from the ZIP archive archive.zip.
  30. find - Search for files and directories
    • find /home/user -name file.txt - searches for the file file.txt in the directory /home/user and its subdirectories.
  31. grep - Search for a pattern in a file
    • grep 'error' log.txt - searches for the word ‘error’ in the file log.txt.
  32. sed - Stream editor for filtering and transforming text
    • sed 's/old_text/new_text/g' file.txt - replaces all occurrences of old_text with new_text in file.txt.
  33. awk - Text processing and data extraction
    • awk '{print $1}' file.txt - prints the first column of file.txt.
  34. echo - Print a message to the terminal
    • echo 'Hello World!' - prints ‘Hello World!’ to the terminal.
  35. date - Display or set the system date and time
    • date - displays the current system date and time.
  36. cal - Display a calendar
    • cal - displays a calendar of the current month.
  37. history - Display the command history
    • history - displays the list of commands executed in the terminal.
  38. du - Estimate file space usage
    • du -h file.txt - displays the disk usage of file.txt in human-readable format.
  39. df - Show disk usage and free space
    • df -h - displays the disk usage and free space of all the mounted filesystems in human-readable format.
  40. free - Display system memory usage
    • free -h - displays the system memory usage in human-readable format.
  41. uname - Display system information
    • uname -a - displays all the system information, including the operating system, kernel version, and hardware architecture.
  42. whoami - Display the current user
    • whoami - displays the name of the current user.
  43. id - Display user and group information
    • id - displays the user and group information of the current user.
  44. passwd - Change user password
    • passwd - changes the password of the current user.
  45. useradd - Create a new user account
    • sudo useradd newuser - creates a new user account named newuser.
  46. usermod - Modify user account
    • sudo usermod -aG groupname username - adds the user username to the group groupname.
  47. userdel - Delete a user account
    • sudo userdel username - deletes the user account username.
  48. groupadd - Create a new group
    • sudo groupadd newgroup - creates a new group named newgroup.
  49. groupmod - Modify a group
    • sudo groupmod -n newname oldname - renames the group oldname to newname.
  50. groupdel - Delete a group
    • sudo groupdel groupname - deletes the group named groupname.