Linux is a powerful operating system that provides users with a vast array of tools and commands to perform various tasks. Whether you are a beginner or an experienced user, it is essential to have a list of the most commonly used Linux commands to navigate and manage your system more efficiently.

Basic command

• whoami: This command displays the username of the current user.

  Example:

    (base) aadarsh-MacBook-Pro:~ aadarsh$ whoami
    aadarsh  ttys002  Apr 16 13:55
  

Navigation Commands

Navigation commands are used to move around the file system and access different directories. Here are some of the most commonly used navigation commands:

• cd: Change directory: This command allows you to change the current working directory to a specified directory. For example, cd /home/user will change the current directory to the user's home directory.

  cd and cd~ both act as same in the mac terminal.

  Example:

    (base) aadarsh-MacBook-Pro:~ aadarsh$ cd ~
    (base) aadarsh-MacBook-Pro:~ aadarsh$
  

• pwd: This will display the full path of the current working directory.

    (base) aadarsh-MacBook-Pro:~ aadarsh$ pwd
    /Users/aadarsh
  

• ls: List contents of a directory: This command lists the files and directories in the current working directory. You can also use ls with options to display additional information such as file permissions, ownership, and size.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls
    example.txt
  

  • ls -a: Lists all contents of a directory, including hidden files and directories.

Example:

    ls -a

• ls -l: List contents of a directory: This command lists the files and directories in the current working directory with additional information such as file permissions, ownership, and size.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -l
    total 0
    -rw-r--r--  1 aadarsh  staff  0 Apr 16 15:11 example.txt
  

• ls -al: This command lists all files and directories in the current working directory, including hidden files and directories, with additional information such as file permissions, ownership, size, and modification time.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -al
    total 0
    drwxr-xr-x  3 aadarsh  staff  96 Apr 16 15:11 .
    drwxr-xr-x@ 3 aadarsh  staff  96 Apr 16 14:29 ..
    -rw-r--r--  1 aadarsh  staff   0 Apr 16 15:11 example.txt
  

  In this example, the ls -al command lists all files and directories in the current working directory, including hidden files and directories. The output shows that the current working directory contains a file called example.txt, along with information about the file's permissions, ownership, size, and modification time.

• ls -R: List contents of a directory and subdirectories: This command lists the files and directories in the current working directory and all its subdirectories recursively.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -R
    .:
    docs        example.txt
  
    ./docs:
  

  In this example, the ls -R command lists the files and directories in the directory aditya and all of its subdirectories recursively. Since there is only one directory docs and it is empty, the output shows only the directory names.

• mkdir: Create a new directory: This command creates a new directory with the specified name.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ mkdir docs
    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls
    docs        example.txt
  

  • mkdir -p: Create a new directory and its parent directories if they do not exist: This command creates a new directory with the specified name and its parent directories if they do not exist. This option is useful for creating directory trees with a single command.

    Example:

      (base) aadarsh-MacBook-Pro:aditya aadarsh$ mkdir -p doc/newdoc/newnewdoc
      (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -R
      doc        example.txt
    
      ./doc:
      newdoc
    
      ./doc/newdoc:
      newnewdoc
    
      ./doc/newdoc/newnewdoc:
    

    In this example, the mkdir -p command creates a new directory called newnewdoc inside the directory newdoc. If any of these directories do not exist, the mkdir -p command creates them as well.

• rmdir: Remove an empty directory: This command removes an empty directory.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls
    docs        example.txt
    (base) aadarsh-MacBook-Pro:aditya aadarsh$ rmdir docs
    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls
    example.txt
  

  • rmdir -p :The rmdir -p command is used to remove a directory and its parent directories if they are empty. This option is useful for removing entire directory trees with a single command.

    For example, the command rmdir -p /home/user/testdir will remove the directory /home/user/testdir, as well as any parent directories that are empty.

    Note that the -p option is not available in all versions of the rmdir command. If you are using a version that does not support this option, you can use the rm command with the -r option to remove a directory and its contents recursively.

    Example:

      (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -R
      doc        example.txt
    
      ./doc:
      newdoc
    
      ./doc/newdoc:
      newnewdoc
    
      ./doc/newdoc/newnewdoc:
      (base) aadarsh-MacBook-Pro:aditya aadarsh$ rmdir -p doc/newdoc/newnewdoc/ 
      (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls -R
      example.txt
    

File Management Commands

File management commands are used to create, copy, move, rename, and delete files. Here are some of the most commonly used file management commands:

• touch: Create a new file: This command creates a new file with the specified name.

  Example:

    (base) aadarsh-MacBook-Pro:aditya aadarsh$ touch example.txt
    (base) aadarsh-MacBook-Pro:aditya aadarsh$ ls
    example.txt
  

• cp: Copy a file: This command copies a file from one location to another. You can use cp with options to preserve file attributes such as ownership, permissions, and timestamps.

  Example:

    cp file1.txt backup/
  

  • cp -r directory1 directory2: Copy a directory and its contents: This command copies a directory and all its contents to a new location. The r option is used to copy directories recursively.

    Example:

      cp -r directory1 directory2
    

    In this example, the cp command copies directory1 and all its contents to a new directory called directory2.

  • cp -u file1.txt file2.txt: Copy a file only if it is newer: This command copies file1.txt to file2.txt only if file1.txt is newer than file2.txt.

    Example:

      cp -u file1.txt file2.txt
    

    In this example, the cp command copies file1.txt to file2.txt only if file1.txt is newer than file2.txt.

  • cp -p file1.txt file2.txt: Copy a file with permissions and timestamps preserved: This command copies file1.txt to file2.txt and preserves the file's permissions and timestamps.

    Example:

      cp -p file1.txt file2.txt
    

    In this example, the cp command copies file1.txt to file2.txt and preserves the file's permissions and timestamps.

• mv: Move or rename a file: This command moves a file from one location to another or renames a file.

  • mv file1.txt directory: Move a file to a directory: This command moves a file to a specified directory.

    Example:

      mv file1.txt docs/
    

    In this example, the mv command moves file1.txt to a directory called docs.

  • mv file1.txt newfile.txt: Rename a file: This command renames a file.

    Example:

      mv file1.txt newfile.txt
    

    In this example, the mv command renames file1.txt to newfile.txt.

  • mv directory1 directory2: Move a directory: This command moves a directory to a new location.

    Example:

      mv directory1 docs/
    

    In this example, the mv command moves directory1 to a directory called docs.

  • mv -i file1.txt directory: Move a file with confirmation: This command moves a file to a specified directory and prompts for confirmation before overwriting an existing file.

    Example:

      mv -i file1.txt docs/
    

    In this example, the mv command moves file1.txt to a directory called docs and prompts for confirmation before overwriting an existing file.

  • mv -u file1.txt file2.txt: Move a file only if it is newer: This command moves file1.txt to file2.txt only if file1.txt is newer than file2.txt.

    Example:

      mv -u file1.txt file2.txt
    

    In this example, the mv command moves file1.txt to file2.txt only if file1.txt is newer than file2.txt.

  • mv -n file1.txt directory: Move a file if it does not exist: This command moves a file to a specified directory only if a file with the same name does not already exist in the directory.

    Example:

      mv -n file1.txt docs/
    

    In this example, the mv command moves file1.txt to a directory called docs only if a file with the same name does not already exist in the directory.

  • mv -b file1.txt directory: Move a file with backup: This command moves a file to a specified directory and creates a backup of any existing file with the same name.

    Example:

      mv -b file1.txt docs/
    

    In this example, the mv command moves file1.txt to a directory called docs and creates a backup of any existing file with the same name.

• rm: Remove a file: This command removes a file. You can use rm with options to force deletion or prompt for confirmation.

  Example:

  • rm file1.txt: Remove a file: This command removes the file file1.txt.

    Example:

      rm file1.txt
    

  • rm -i file1.txt: Remove a file with confirmation: This command prompts for confirmation before removing the file file1.txt.

    Example:

      rm -i file1.txt
    

  • rm -r directory1: Remove a directory and its contents recursively: This command removes the directory directory1 and all its contents recursively.

    Example:

      rm -r directory1
    

  • rm -f file1.txt: Remove a file without confirmation: This command removes the file file1.txt without prompting for confirmation.

    Example:

      rm -f file1.txt
    

  • rm -rf directory1: Remove a directory and its contents recursively without confirmation: This command removes the directory directory1 and all its contents recursively without prompting for confirmation.

    Example:

      rm -rf directory1
    

• nano: Open a text editor: This command opens a text editor to create or edit a file.

  Example:

    nano file4.txt
  

• cat: command in Linux is used to concatenate files and display the output on the terminal. Here are a few examples of using the cat command:

  • cat file.txt: Display the contents of a file: This command displays the contents of a file on the terminal.

    Example:

      cat file.txt
    

    In this example, the cat command displays the contents of the file file.txt on the terminal.

  • cat file1.txt file2.txt: Concatenate multiple files: This command concatenates the contents of multiple files and displays the output on the terminal.

    Example:

      cat file1.txt file2.txt
    

    In this example, the cat command concatenates the contents of file1.txt and file2.txt and displays the output on the terminal.

  • cat file1.txt > file2.txt: Redirect output to a file: This command redirects the output of the cat command to a file.

    Example:

      cat file1.txt > file2.txt
    

    In this example, the cat command reads the contents of file1.txt and writes them to file2.txt.

  • cat file1.txt >> file2.txt: Append output to a file: This command appends the output of the cat command to a file.

    Example:

      cat file1.txt >> file2.txt
    

    In this example, the cat command reads the contents of file1.txt and appends them to file2.txt.

  • cat -n file.txt: Display line numbers: This command displays the contents of a file with line numbers.

    Example:

      cat -n file.txt
    

    In this example, the cat command displays the contents of file.txt with line numbers.

  • cat file1.txt | grep "pattern": Search for a pattern: This command searches the contents of a file for a specified pattern.

    Example:

      cat file1.txt | grep "pattern"
    

    In this example, the cat command reads the contents of file1.txt and pipes them to the grep command, which searches for the pattern "pattern" in the file.

    • cat file1.txt | grep -v "pattern": Display lines not containing a pattern: This command displays the lines of a file that do not contain a specified pattern.

      Example:

        cat file1.txt | grep -v "pattern"
      

      In this example, the cat command reads the contents of file1.txt and pipes them to the grep command with the -v option, which displays the lines of the file that do not contain the pattern "pattern."

    • cat file1.txt | head -n 10: Display the first 10 lines of a file: This command displays the first 10 lines of a file.

      Example:

        cat file1.txt | head -n 10
      

      In this example, the cat command reads the contents of file1.txt and pipes them to the head command with the -n option, which displays the first 10 lines of the file.

    • cat file1.txt | tail -n 10: Display the last 10 lines of a file: This command displays the last 10 lines of a file.

      Example:

        cat file1.txt | tail -n 10
      

      In this example, the cat command reads the contents of file1.txt and pipes them to the tail command with the -n option, which displays the last 10 lines of

• grep: command is used to search for patterns within files. Here are some examples of using the grep command in Linux:

  • grep "pattern" file.txt: Search for a pattern in a file: This command searches for the specified pattern in the file and displays the lines that contain the pattern.

    Example:

      grep "example" file.txt
    

    In this example, the grep command searches for the pattern "example" in the file file.txt.

  • grep -i "pattern" file.txt: Search for a pattern in a case-insensitive manner: This command searches for the specified pattern in the file, ignoring case, and displays the lines that contain the pattern.

    Example:

      grep -i "example" file.txt
    

    In this example, the grep command searches for the pattern "example" in the file file.txt, ignoring case.

  • grep -r "pattern" directory: Search for a pattern recursively in a directory: This command searches for the specified pattern in all files within the directory and its subdirectories, and displays the lines that contain the pattern.

    Example:

      grep -r "example" directory
    

    In this example, the grep command searches for the pattern "example" in all files within the directory directory and its subdirectories.

  • grep -v "pattern" file.txt: Display lines not containing a pattern: This command displays the lines of a file that do not contain the specified pattern.

    Example:

      grep -v "example" file.txt
    

    In this example, the grep command displays the lines of the file file.txt that do not contain the pattern "example".

  • grep -c "pattern" file.txt: Count the number of lines containing a pattern: This command counts the number of lines in a file that contain the specified pattern.

    Example:

      grep -c "example" file.txt
    

    In this example, the grep command counts the number of lines in the file file.txt that contain the pattern "example".

  • grep -n "pattern" file.txt: Display line numbers: This command displays the lines of a file that contain the specified pattern, along with their line numbers.

    Example:

      grep -n "example" file.txt
    

    In this example, the grep command displays the lines of the file file.txt that contain the pattern "example", along with their line numbers.

File Permissions Commands

File permission commands are used to manage file and directory permissions. Here are some of the most commonly used file permission commands:

  read, write and execute permissions

• chmod: Change file permissions: This command changes the permissions of a file or directory. You can use chmod with options to set permissions for owner, group, and other users.

  Example:

    chmod 755 file.txt
  

  In this example, the chmod command sets the file permissions of file.txt to rwxr-xr-x, which means that the owner has read, write, and execute permissions, while the group and other users have read and execute permissions.

  • chmod u+x file.txt: This command adds execute permission for the owner of the file.

Example:

    chmod u+x file.txt

In this example, the chmod command adds execute permission for the owner of the file file.txt.

• chmod g+w file.txt: This command adds write permission for the group of the file.

Example:

    chmod g+w file.txt

In this example, the chmod command adds write permission for the group of the file file.txt.

• chmod o-r file.txt: This command removes read permission for other users of the file.

Example:

    chmod o-r file.txt

In this example, the chmod command removes read permission for other users of the file file.txt.

• chmod -R 755 directory: This command sets the permissions of all files and directories in the specified directory to rwxr-xr-x.

Example:

    chmod -R 755 directory

In this example, the chmod command sets the permissions of all files and directories in the directory directory to rwxr-xr-x.

System Information Commands

System information commands are used to display information about the system's hardware and software. Here are some of the most commonly used system information commands:

• top: Display system processes: This command displays the system processes' real-time status, including CPU and memory usage.

  Example:

    top
  

• du: Estimate file space usage: This command displays the disk space used by files and directories. By default, du displays the disk space used by the current directory and its subdirectories.

  Example:

    du -h
  

  In this example, the du command displays the disk space used by the current directory and its subdirectories in a human-readable format. The -h option stands for "human-readable."

  • du -h file.txt: This command displays the disk space used by the file file.txt.

Example:

    du -h file.txt

In this example, the du command displays the disk space used by the file file.txt in a human-readable format.

• du -sh directory: This command displays the total disk space used by the directory directory in a human-readable format.

Example:

    du -sh directory

In this example, the du command displays the total disk space used by the directory directory in a human-readable format.

• free: Display system memory usage: This command displays the system's available, used, and free memory.

  Example:

    free
  

• df: Display disk space usage: This command displays the disk space usage of the file system.

  Example:

    df
  

• uname: Display system information: This command displays the system's kernel version, operating system, and processor architecture.

  Example:

    uname -a
  

  • uname -s: This command displays the operating system name.

    Example:

      (base) aadarsh-MacBook-Pro:~ aadarsh$ uname -s
      Darwin
    

  • uname -r: This command displays the operating system release number.

    Example:

      (base) aadarsh-MacBook-Pro:~ aadarsh$ uname -r
      20.3.0
    

  • uname -m: This command displays the machine hardware name.

    Example:

      (base) aadarsh-MacBook-Pro:~ aadarsh$ uname -m
      x86_64
    

• history: Display command history: This command displays the command history of the current user.

  Example:

    history
  

Network Commands

Network commands are used to configure and troubleshoot network connections. Here are some of the most commonly used network commands:

• ping: Test network connectivity: This command tests the network connectivity to a specified network host.

  Example:

    ping 8.8.8.8
  

• ifconfig: Display network interface information: This command displays the network interface's configuration information.

  Example:

    ifconfig
  

• netstat: Display network connections and statistics: This command displays the network connections and statistics.

  Example:

    netstat
  

• ssh: Connect to a remote server: This command establishes a secure shell connection to a remote server.

  Example:

    ssh user@remote_host
  

• scp: Copy files securely between servers: This command securely copies files between servers.

  Example:

    scp /path/to/file user@remote_host:/path/to/destination
  

  • More examples

    Example 1:

      scp file.txt user@remote_host:/path/to/destination
    

    In this example, the file.txt is copied from the local machine to the remote server remote_host at /path/to/destination.

    Example 2:

      scp -r /path/to/directory user@remote_host:/path/to/destination
    

    In this example, the entire directory is copied recursively from the local machine to the remote server remote_host at /path/to/destination.

    Example 3:

      scp user@remote_host:/path/to/file.txt /path/to/destination
    

    In this example, the file.txt is copied from the remote server remote_host to the local machine at /path/to/destination.

    Example 4:

      scp -r user@remote_host:/path/to/directory /path/to/destination
    

    In this example, the entire directory is copied recursively from the remote server remote_host to the local machine at /path/to/destination. <insert-here/>

Remember, this is just a small selection of the many commands available in Linux. You can use the man command followed by the command name to display the command's manual page with detailed information about the command's usage, options, and examples. Learning these basics will help you navigate and manage your system more efficiently.

Linux is a powerful operating system that provides users with a vast array of tools and commands to perform various tasks. Whether you are a beginner or an experienced user, it is essential to have a list of the most commonly used Linux commands to navigate and manage your system more efficiently.

Summary

This document provides a cheat sheet of Linux commands for managing files, file permissions, system information, and network connections. The document includes examples of commonly used commands.

File Commands

File commands are used to manage files and directories. Here are some of the most commonly used file commands:

File Permissions Commands

File permission commands are used to manage file and directory permissions. Here are some of the most commonly used file permission commands:

System Information Commands

System information commands are used to display information about the system's hardware and software. Here are some of the most commonly used system information commands:

Network Commands

Network commands are used to configure and troubleshoot network connections. Here are some of the most commonly used network commands:

Try these Questions!

1. Create a new directory called "testdir" using the mkdir command.

2. Change the current directory to "testdir" using the cd command.

3. Create a new text file called "testfile.txt" using the touch command.

4. Open the text file "testfile.txt" in a text editor using the nano command.

5. Write the following text in the file:

Hello, World!
This is a test file.

1. Save and exit the text editor using the key combination Ctrl+X, Y, and Enter.

2. Display the contents of the file "testfile.txt" using the cat command.

3. Change the permissions of the file "testfile.txt" to read, write, and execute for the owner, and read-only for the group and others using the chmod command.

4. Display the permissions of the file "testfile.txt" using the ls -l command.

5. Copy the file "testfile.txt" to a new file called "testfile_copy.txt" in the same directory using the cp command.

6. Rename the file "testfile_copy.txt" to "newfile.txt" using the mv command.

7. Display the contents of the file "newfile.txt" using the cat command.

8. Remove the file "newfile.txt" using the rm command.

9. Remove the directory "testdir" using the rmdir command.

Few more questions

1. File Management: You need to copy a file named data.txt from /home/user1/ directory to /home/user2/ directory. Also, create a new directory named backup in /home/user2/ directory and move the copied file to this new directory.

2. File Permissions: You need to set the permissions of a file named confidential.txt to rw------- so that only the owner of the file can read and write to it.

3. System Information: You need to find out the amount of free memory available on the system.

4. Network Connections: You need to test the network connectivity to a remote server with IP address 192.168.1.10 using the ping command.