The management of users and permissions in a Linux system is crucial for security and data integrity. Each file is associated with a owner, which has specific access rights, dictated by a set of permissions. These permissions generally fall into three categories: reading, writing And execution.
To modify the permissions, use the command chmod, which facilitates management using a system of symbolic or numerical notations. For example, a permission represented by rwx for the owner, rx for the group and r for other users. To ensure security when making changes, it is recommended to save the original permissions before making changes.
The order chown allows you to change the owner of a file, while the command groups helps to list users by group. For effective rights management, it is essential to understand the concepts of property and of extended permissions.
Finally, applying permissions in a way recursive can also be done, making it easier to manage permissions on entire directories.
Managing users and permissions on Linux
User management and permissions in a Linux operating system is an essential skill for ensuring file security and organization. In this article, we will discuss the different ways to manage users, as well as access permissions to files and directories. You will learn how to use key commands and understand how access rights work in Linux.
Understanding users and groups
user has specific rights that define what he can do with files and directories. It is important to note that users can be grouped into groups, which allows permissions to be assigned or modified collectively rather than individually. To display the list of all users, you can consult the file /etc/passwd.
Users
Each user has their own unique identity represented by a name and a numeric identifier (UID). When you create a new user, you can specify various settings, including their default password and group. This ensures that each user is clearly defined in the system.
Groups
THE groups allow you to group users to simplify permission management. Each group has a numerical identifier (GID) and can contain several users. Groups allow you to grant access rights to multiple users simultaneously, simplifying operations in a multi-user environment.
Permission Fundamentals
Permissions in Linux are fundamental to file security. Each file and directory has three access levels: owning user, owning group, and other users. The rights of each category include reading (r), writing (w) and execution (x).
Symbolic and octal notation
Permissions can be represented in two ways: in notation symbolic And octal. In symbolic notation, permissions are written in the form of rwx for the user owner, rx for the group and r for other users. Octal notation uses numbers 0 through 7 to represent the same permissions.
Change permissions
To modify the permissions of a file or directory, use the command chmod. This command allows you to add or remove permissions to users, groups or other users. Using numeric values for permissions can also simplify management. For example, we can define the permissions of a file using a simple octal value.
Recursive application
In many cases, it is desirable to change the permissions of a directory and all the files it contains. To do this, simply add the option -R to order chmod, which applies the changes recursively.
User privilege management
User privileges can also be managed through role assignment. For example, users can be added to groups specific, thus offering them varied levels of access without having to modify their individual permissions.
Saving permissions
In a sensitive context, it may be useful to save the permissions of a file or directory before making changes. This allows you to restore the original permissions in case of accidental modification. You can use tools like getfacl to back up and restore access control lists (ACLs).
View current permissions
To view the permissions of a file or directory, use the command ls -l. This will display a detailed list of files, including their permissions, owner and associated group. A good understanding of this command is essential for any Linux administrator.
Useful links to deepen your knowledge
To learn more about how Linux works and how it is managed, feel free to consult these resources: