Day 6 of the #90daysofdevops: Understanding File Permissions and Access Control Lists

Welcome to the sixth day of the #90DaysOfDevOps challenge! In this blog post, we will delve into the intricacies of File Permissions and Ownership in Linux, breaking down complex concepts into simple, understandable terms. Today, we'll not only learn how to modify permissions and ownership but also explore the realm of Access Control Lists (ACL) using powerful commands such as "getfacl" and "setfacl." Let's unravel the secrets of secure file management! ?????

Introduction

File permissions in Linux play a crucial role in determining who can access, modify, and execute files and directories. They are fundamental for ensuring security and control over sensitive data and system resources. There are three main categories of users with distinct permissions for a file:

• Owner (user) ??: The user who creates or owns the file.
• Group ??: A set of users sharing the same access permissions.
• Others ????: All users not included in the owner or group category.

Each category can have three types of permissions:

• Read (r) ??: Allows users to view the content of a file or the list of a directory.
• Write (w) ??: Permits users to modify or delete files and directories.
• Execute (x) ??♂?: Enables users to run executable files or access directories to list their contents.

File permissions are represented using a three-character string for each category. For instance, "rw-r—r—" means the owner has read and write permissions, while the group and others have only read permissions. To view and modify file permissions, you can use the "ls -l" command to display permissions and the "chmod" command to change them.

Task 1: Change the Permission of Files/Directories

In Linux, modifying file or directory permissions involves using the "chmod" command. There are two methods: the Symbolic method (ugo) and the Absolute method.

Symbolic Method (ugo):

• "u" stands for User
• "g" stands for Group
• "o" stands for Other

For example, to add execute permission for the user, add write permission for the group, and remove read permission for others, you can use:

chmod u+x, g+w, o-r file.txt 
ls -l file.txt        

Absolute Method:

In this method, numbers represent permissions (4 for Read, 2 for Write, 1 for Execute). For example:

chmod 632 test.txt 
ls -l file.txt        

Using numbers in the Absolute method provides a quick and precise way to manage permissions in Linux.

Task 2: Change the Ownership of Files/Directories

To change the ownership of a file, the "chown" command is used, but only the root user can perform this action:

sudo chown ubuntu file.txt 
ls -l file.txt        

After executing the command, the user "ubuntu" becomes the owner of the "file.txt" file.

Task 3: Change the Group Permission of Files/Directories

The group ownership of a file or directory can be changed using the "chgrp" command, restricted to the root user:

chgrp ubuntu devtxt.txt 
ls -l file.txt        

With this command, the group ownership of "file.txt" changes to "ubuntu."

Access Control Lists (ACL)

ACLs provide precise control over file permissions, allowing specific access for users or groups. Two essential ACL commands are "getfacl" (??) to view ACL settings and "setfacl" (???) to modify entries.

To view ACL settings of a file:

getfacl file.txt        

To change ACL entries and grant specific permissions to users or groups:

sudo setfacl -m g::r--,o::r-- file.txt 
getfacl file.txt        

ACLs offer a sophisticated way to handle file permissions, especially in situations requiring special access for specific users or groups.

Conclusion

Congratulations on completing Day 6 of the #90DaysOfDevOps challenge! Today, we delved into the essential aspects of file permissions, understanding their significance in ensuring secure and controlled access to files and directories in Linux. We explored tasks related to changing permissions, ownership, and group permissions, along with a deep dive into Access Control Lists (ACL) using the helpful commands "getfacl" and "setfacl." Armed with this knowledge, you can confidently manage file access and uphold data security in your Linux environment. ????