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August 31, 2023
Updated August 31, 2023

File permissions in Linux

Debian Maintenance VPS


Access and permission control for files serve critical purposes in the realm of data management and security:

  • Enhanced Security: The implementation of access control mechanisms ensures that files can only be accessed by individuals who possess the necessary permissions. This bolstered security prevents unauthorized parties from gaining entry to sensitive or confidential data.
  • Preservation of Confidentiality: By instituting precise permission settings, confidentiality is safeguarded. Unauthorized exposure of sensitive information to unintended users, which could result in breaches or leaks, is effectively averted.
  • Safeguarding Integrity: Permission control plays a pivotal role in maintaining the integrity of files. Unauthorized alterations or tampering with crucial files are thwarted, ensuring the reliability and accuracy of data.
  • Adherence to Regulations: Numerous industries and organizations are mandated to adhere to regulatory standards that mandate stringent access controls. The establishment of proper permission structures aids in meeting these compliance requisites and evading legal ramifications.
  • Mitigation of Data Loss: Through access control, the inadvertent loss of data is mitigated. Instances where users lacking appropriate permissions accidentally delete or overwrite vital files are curtailed.
  • Resource Optimization: Permission management optimizes the allocation of resources. By limiting access to specific users or groups, unnecessary resource consumption is averted, and pertinent parties are granted access.

In summation, access and permission control are instrumental in upholding the security, confidentiality, and soundness of files and data. They thwart unauthorized access, prevent data breaches and losses, and contribute to regulatory compliance.


  • Root rights;
  • Debian 12 or higher version;
  • Several knowledge about work OS ;
  • Internet connection.

Permission and attributes on Linux

In the Linux environment, the management of files and permissions is a thorough and intricate process, designed to ensure the utmost security and precision in handling data. Here's a more in—depth look. Linux recognizes a spectrum of file types, including regular files, directories, symbolic links, and devices. Each type possesses unique attributes and permissions. In the Debian 12 we can check all attributes and permission of all users by the command below:

ls -l
List of permission
Screenshot №1 — List of permission

But if we want to chek out determine file, then we need to use command below, indicate file that you want to check:

ls -l /etc/network/interfaces
Single file
Screenshot №2 — Single file

Let's be clear and explain every parameter in that screen:

  • The -rw-r--r-- raw means the initial trio corresponds to the owner's permissions, the second to the group, and the third to other users. That file is not directory or link, because first sign is dash. The rw- means owner have right to read, write, but has not for execute. The r-- means group of owner have only read rights, also at the last triplet of other users;
  • The means that file have one hard link;
  • The root:root in that case parameter indicates owner and group for that file;
  • The size of that file 175 bites;
  • Data of last changes November, 8 2022 and name if file Interfaces.

Each file is linked to an individual user (owner) and a designated group. The act of creating a file establishes the creator as its owner, while a specific group is assigned to the file. Linux segments permissions into three categories: user, group, and others. Every category can be assigned distinct read, write, and execute permissions. And we can change all of that if we have right and straight permission to that by the chmod utility.

Permissions are also translatable into numeric forms, where read (r) equates to 4, write (w) to 2, and execute (x) to 1. The cumulative sum represents the numerical permission, such as 755.

chmod 755 interfaces
Chmod numeric
Screenshot №3 — Chmod numeric

But if we want to deny all permissions to the all type of users, we need to write command below:

chmod 000 interfaces
Chmod numeric deny
Screenshot №4 — Chmod numeric deny

The chmod command serves to modify permissions. This command accepts both symbolic and numeric notations. For instance, chmod u+w filename confers write permission to the owner. The u means owner, g assign to group, o for others and a for all . Then we indicate + or - or = to add, delete, indicate explicitly permission for users:

chmod u+rwx interfaces && chmod go-rwx interfaces
Chmod symbolic
Screenshot №5 — Chmod symbolic

Or we can use equal command:

chmod u=rwx, go= interfaces

If you want to save write permission for other and group users, but you need protect them from delete, then use command below:

chmod +t interfaces

That's basics of permission on the system, but what if we need more?

Utility for addition control permission

In Linux, the core kernel provides a solid foundation for the operating system, but it doesn't include all possible features and functionalities by default. The reason additional modules and packages are required for controlling access and file permissions is to give system administrators and users the flexibility to tailor the system's behavior to their specific needs. Here are a few reasons why this approach is taken:

  • Modularity: The Linux kernel is designed to be modular, which means that various functionalities can be compiled as loadable modules rather than being directly integrated into the core kernel. This keeps the core kernel relatively lightweight and allows users to add only the specific modules they need. This approach improves system efficiency and reduces the risk of unnecessary code affecting the stability of the kernel.
  • Flexibility: Not all users and systems require the same level of access control and file permissions. By offering additional modules and packages, Linux distributions allow administrators to choose the appropriate tools for their specific security requirements. This flexibility ensures that systems can be fine—tuned to meet various needs, whether it's a simple desktop system or a complex server environment.
  • Security: Offering access control and file permission modules as separate packages ensures that users only install what they need. This reduces the attack surface of the system, as unnecessary features are not present. It also allows for regular updates and security patches to be applied specifically to these modules, enhancing the overall security of the system.

As you could highlight standart access control system have several lack: there isn't system protect by random deletion significant file, integrity file system and etc. Let's upgrade system!

Umask Usage: The umask command regulates default permissions for novel files and directories. It achieves this by deducting the specified mask from the maximum permission value to set defaults. By the default we can see that list of permission:

Default permission
Screenshot №6 — Default permission

You can see default list of permission for file, lets change it:

umask u=rwx,go=
Screenshot №7 — Umask

That solution will help for time before you turn of machine or connection, for more long working that system you can add to the .bashrc or bash_login needed raw!


The combination of well—defined access controls, precise permission settings, and the flexibility to add supplementary tools empowers system administrators to create a secure and tailored environment for managing files and data in the Linux ecosystem.

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