Guide: Protect your files and directories with Linux ACLs

In the Linux operating system, ACL (Access Control List) is a very powerful tool that can be used to more finely control access permissions to files and directories. Through ACL, users can set specific permissions for specific users or user groups, not just limited to the traditional read, write, and execute permissions for users and groups. This article will introduce you how to use ACL to protect your files and directories, and provide specific code examples for reference.

What is ACL?

In traditional Linux permission management, the permissions of files and directories are determined by the three identities of the owner, the group to which they belong, and other users. However, in some cases, this coarse-grained permission control may not meet the needs of users. At this time, you can use ACL for more detailed permission management.

ACL allows users to set specific permissions for specific users or user groups, including read, write, execute, etc. Through ACL, users can more precisely control access permissions to files and directories and improve file security.

Install the ACL tool

Most Linux distributions come with the ACL tool, but if your system does not have it installed, you can use the following command to install it:

sudo apt-get install acl    # 对于Debian/Ubuntu系统
sudo yum install acl        # 对于CentOS/RHEL系统

Install Once completed, you can start using ACLs to control permissions on files and directories.

Setting ACL Example

1. Setting ACL for a specific user

Suppose we want to set up an ACL named example. txt file, only user user1 can read and write this file, other users can only read it. First, we can use the setfacl command to set the ACL:

setfacl -m u:user1:rw example.txt

This command represents the user user1 setting of the example.txt file. Write permission.

2. Set ACL for a specific user group

If we want a certain user group to have full access to a directory, we can use the following Command:

setfacl -m g:group1:rwx /path/to/directory

This command means setting read, write, and execution permissions for the user group group1 of the /path/to/directory directory.

3. View ACL

To view the ACL settings for a specific file or directory, you can use the getfacl command:

getfacl example.txt

This will display the ACL information of the example.txt file, including the permissions of the user and user group.

Common operations of ACL

In addition to the above examples, ACL also has many other common operations, such as modifying ACL, removing ACL, applying ACL to subdirectories, etc. The following are some commonly used ACL operations:

• Modify ACL

setfacl -m u:user1:rx example.txt   # 为用户user1添加读取和执行权限

• Remove ACL

setfacl -x u:user1 example.txt      # 移除用户user1对example.txt的ACL设置

• Applying ACLs to subdirectories

setfacl -R -m g:group1:rwx /path/to/directory   # 递归应用ACL到目录及其子目录

Summary

By using ACLs, you have more flexibility in controlling files and Directory access permissions to improve system security. This article introduces the basic concepts, installation methods and common ACL operations of ACL, hoping to help you better protect your files and directories.

In Linux systems, ACL is a very powerful tool that can help users achieve more detailed permission management. If you need more precise control over file permissions, try using ACLs to achieve your goals.

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