Introduction:
In the world of Linux systems, file permissions play a crucial role in ensuring the security and privacy of files and directories. They regulate who can access certain files and what actions they can perform on them. In this blog, we will explore the various types of file permissions, how to assign them and delve into Access Control Lists (ACLs) for more flexible access management.
Creating and Checking File Details:
To start, let's create one file using the 'touch' command:
Managing File Permission With Alphabetical:
File permissions are at the core of the Linux security model, governing access to files and directories. There are three types of permissions:
Basic Permission:
The owner (u): Permissions for the owner of the file.
Group (g): Permissions for the members of the file's group.
Others (o): Permissions for all other users.
Each type of permission can be granted in three modes:
Read (r): Allows viewing the content of the file.
Write (w): Permits modifying the file and its content.
Execute (x): Enables execution of the file if it is executable.
Let's create a file named "test1" and check its permissions using the ls -ltr command:
Changing File Permissions:
To modify file permissions, we use the chmod command. To grant permissions, we use the + symbol, and to remove permissions, we use the - symbol.
For example, to give read, write, and execute access to the user for the "test1" file:
Managing File Permission With Numerically:
Linux also allows setting permissions numerically using three-digit numbers. Each permission (read, write, execute) is assigned a numeric value:
Read (r): 4
Write (w): 2
Execute (x): 1
Permissions | Numeric | Meaning |
drwxr-xr-x | 755 | Directory, accessible by everyone but only writable by the owner |
-rw-r--r-- | 644 | File, readable by everyone but can only be modified by the owner |
-rwxrwxrwx | 777 | The file is readable (and executable) by anybody |
-rw------- | 600 | The file can only be accessed by the owner, inaccessible to everyone else |
Let's create another file named "test2" and check its permissions using ls -ltr command:
To give write and execute access to others and remove all access from user and group for the "test2" file:
Access Control List (ACL):
ACLs provide a more fine-grained permission mechanism. They allow granting permissions to specific users or groups that are not members of the file's group. Before using ACLs, you must install the acl package using sudo apt install acl command.
To view and modify ACLs, you can use getfacl and setfacl commands. Let's check the ACLs of the "test2" file.
Let’s create one user and assign the read, write, and execute access to the test2 file.
Conclusion:
Understanding file permissions is crucial for maintaining the security and integrity of your Linux system. Basic permissions and numeric modes provide a simple way to manage access, while ACLs offer more flexibility to grant permissions to specific users and groups. As a Linux user, mastering these concepts empowers you to control access to your files and directories effectively, ensuring the confidentiality and availability of your data.