Understanding file permissions and ownership is crucial for managing a Linux system securely and efficiently. This section will cover the basics of file permissions, how to view and modify them, and the concept of file ownership.

• Read (r): Permission to read the contents of the file.
• Write (w): Permission to modify the contents of the file.
• Execute (x): Permission to execute the file as a program.

• User (u): The owner of the file.
• Group (g): A group of users who share the same permissions.
• Others (o): All other users.

• Symbolic Notation: rwxr-xr--
• Octal Notation: 755

To view the permissions and ownership of a file, use the ls -l command.

Example output:

Explanation:

• -rw-r--r--: File type and permissions.
• 1: Number of hard links.
• user: Owner of the file.
• group: Group owner of the file.
• 1234: File size in bytes.
• Jan 1 12:34: Last modification date and time.
• filename: Name of the file.

The chmod command is used to change the permissions of a file or directory.

Symbolic Mode

Octal Mode

The chown command changes the ownership of a file or directory.

The chgrp command changes the group ownership of a file or directory.

1. Create a file:

   $ touch example.txt
   

2. View the current permissions:

   $ ls -l example.txt
   

3. Change the permissions to rwxr-xr--:

   $ chmod 754 example.txt
   

4. Verify the changes:

   $ ls -l example.txt
   

1. Create a file:

   $ touch example.txt
   

2. Change the owner to newuser and group to newgroup:

   $ sudo chown newuser:newgroup example.txt
   

3. Verify the changes:

   $ ls -l example.txt
   

1. Create a file named testfile.txt.
2. View the permissions and ownership of testfile.txt.

1. Change the permissions of testfile.txt to rwxr-xr--.
2. Verify the changes.

1. Change the owner of testfile.txt to yourusername and group to yourgroup.
2. Verify the changes.

• Mistake: Forgetting to use sudo when changing ownership.

  • Tip: Use sudo to ensure you have the necessary permissions to change ownership.

• Mistake: Incorrectly setting permissions using octal notation.

  • Tip: Double-check the octal values to ensure they match the desired permissions.

In this section, you learned about file permissions and ownership in Linux. You now know how to view and modify permissions using chmod, chown, and chgrp commands. Understanding these concepts is essential for managing files securely and efficiently on a Linux system. In the next section, we will delve into advanced command line skills, starting with using wildcards and regular expressions.