How do accounts work in GNU/Linux?

How do accounts work in GNU/Linux?

In GNU/Linux systems, user accounts are a fundamental concept that plays a crucial role in controlling access to the system's resources and maintaining security. User accounts allow individuals to log in, execute processes, and perform various actions on the system, while maintaining isolation between users' activities and data.

Here's how accounts work in GNU/Linux:

1. Usernames: Each user account is identified by a unique username. Usernames are used to log in to the system and are associated with specific privileges and permissions.

2. User IDs (UIDs): Behind the scenes, each user is assigned a numeric User ID (UID). This UID is used by the system to uniquely identify users. Regular users typically have UIDs starting from 1000, while system users and services have lower UIDs.

3. Group IDs (GIDs): Users can also belong to one or more groups, which define their level of access to various resources. Each group has a numeric Group ID (GID). Group membership allows users to share access to files, directories, and other resources with other users in the same group.

4. Password Authentication: User accounts are protected by passwords. When a user logs in, they must provide their username and password to gain access to the system. Passwords are usually hashed and stored securely in the system's password database. Modern systems often use stronger authentication mechanisms like SSH keys, biometrics, or multi-factor authentication for enhanced security.

5. Home Directories: Each user account has a home directory where they can store their personal files and configuration settings. The home directory is typically located under the /home directory and is named after the user's username (e.g., /home/username).

6. Permissions and Ownership: The Linux filesystem uses a permissions model to control who can access files and directories. Each file and directory has an owner and a group associated with it. The owner and group determine who can read, write, and execute the file. Permissions can also be set for other users who are not the owner or in the group.

7. Root (Superuser) Account: In addition to regular user accounts, there is a special user account called "root" or the "superuser." The root account has unrestricted access to all system resources and can perform tasks that would otherwise be restricted for regular users. The root account should be used sparingly and only for system administration tasks, as misuse can lead to system instability or compromise.

8. sudo: Instead of directly logging in as the root user, modern Linux systems encourage the use of the sudo command to execute privileged commands. Users in the sudoers list (configured in the /etc/sudoers file) can use sudo to temporarily gain superuser privileges for specific commands.

9. Account Management: User accounts can be managed using various command-line tools like useradd, userdel, passwd, and graphical user management tools in desktop environments. System administrators are responsible for creating, modifying, and removing user accounts as needed.

Overall, user accounts in GNU/Linux systems provide a structured and controlled environment, allowing multiple users to work concurrently while maintaining security and isolation between their activities.