How to optimize and adjust file permission settings in Linux systems

How to optimize and adjust the file permission settings of the Linux system

With the continuous development and widespread application of the Linux operating system, there are increasing demands for file permission settings. Reasonable file permission settings can not only protect the security of the system, but also improve the performance and stability of the system. This article will introduce some methods to optimize and adjust file permission settings in Linux systems.

1. Understanding Linux file permissions
   In the Linux system, each file and directory has corresponding permissions. Permissions are divided into three levels: owner (Owner), group (Group) and other users (Other). Each level can set read (Read), write (Write) and execute (Execute) permissions. For example, if the permissions of a file are set to -rw-r--r--, it means that the owner has read and write permissions, and the group to which it belongs and other users only have read permissions.
2. Set appropriate file permissions
   Reasonable file permission settings are the basis for protecting system security. For regular user files, it can be set to 755 (rwxr-xr-x), which means that the owner has read, write, and execute permissions, and the group and other users have only read and execute permissions. For system configuration files and program files, it can be set to 644 (rw-r--r--), which means that only the owner has write permissions, and other users only have read permissions.
3. Set precise file permissions
   Sometimes, we need different users to have different permissions on files in a certain directory, rather than setting them uniformly. This can be achieved by setting the belonging group and user group. For example, create a user group dev, specify the file as the owner of the dev group, and set it to 770 (rwxrwx---), which means that members of the dev group have read, write, and execute permissions, and other users do not have permissions.
4. Use ACL (Access Control List) to control permissions
   ACL is a function for more granular permission control on files and directories. It can set individual permissions for each file or directory, making it more flexible. You can use the setfacl and getfacl commands to set and query ACL permissions. For example, you can use the setfacl command to add read and write permissions to a specific user or user group.
5. Regularly check and repair permission settings
   In order to ensure the security and stability of the system, it is recommended to regularly check and repair file permission settings. You can use commands such as find, chmod, and chown to repair permissions in batches. For example, you can use the find command to find all user directories, and use the chmod command to modify the permissions to 700 (rwx------) to ensure that only the owner has access permissions.
6. Reasonable use of SUID, SGID and sticky bits
   SUID (Set User ID) and SGID (Set Group ID) are special bits in file permissions. When a file has the SUID or SGID bit set, it will temporarily acquire the permissions of the owner or group it belongs to when executing. The sticky bit prevents other users from deleting or renaming files created by other users. Proper use of these special bits can improve system security and flexibility.

To sum up, optimizing and adjusting the file permission settings of the Linux system requires a full understanding and proficiency in the principles and usage of Linux file permissions. Properly setting file permissions can protect system security and improve system performance and stability. In addition, regularly checking and repairing file permissions, using ACL for more refined permission control, and rationally using SUID, SGID, and sticky bits are also important skills for operating file permissions in Linux systems.

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