Basic knowledge of Linux advanced ACL permission Control

1. Advanced permission mechanism, allowing flexible and complex permission settings for files or folders
The most important Entry tag type, which has the following types:
ACL_USER_OBJ: equivalent to the permission of file_owner in Linux
ACL_USER: defines the permission that an additional user can possess for this file.
ACL_GROUP_OBJ: equivalent to permission of group in Linux
ACL_GROUP: defines the permission that an additional group can possess for this file.
ACL_MASK: defines the maximum permissions of ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP.
ACL_OTHER: equivalent to the permission of other in Linux
User: corresponds to ACL_USER_OBJ and ACL_USER
Group: corresponds to ACL_GROUP_OBJ and ACL_GROUP.
Mask: corresponds to ACL_MASK
Other: corresponds to ACL_OTHER
 
2. Open the ACL when you need to mount the file system.
Mount-o acl/dev/sda5/data
Add the acl after ults in/etc/fstab
Acl is enabled for the root partition by default.
 
3. ACL permission for viewing files or directories
Getfacl filename
 
4. Set ACL
Setfacl-m u: username: rwx filename
-M modify
-Delete x. No permission required.
U user
G group
 
5. mask
After ACL is set for the file, the permission of the Group in the file is displayed as a mask, which does not represent the permission of the group.
Mask specifies the maximum permissions of ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP. Excessive permissions are invalid.
The mask does not affect the permission of the object owner.