Standard Linux file permissions are applicable for file owners, groups of files, or everyone else in the system. Using standard permissions, we cannot give multiple users or multiple groups different permissions for a single file. This kind of delicate control is provided using ACLs in Linux. We can give permissions to more than one user or one group for the same file.

File owners or root can set ACLs on individual files or on directories if the filesystem is mounted with ACL support enabled. CentOS 7's default filesystem is XFS, which has built-in ACL support. Although not all applications (such as tar) support ACL, it is still a great functionality available in the Linux system.