In general, plain Unix permissions aren’t sufficient when you have permission requirements that don’t map cleanly to an enterprise’s natural hierarchy of users and groups , HDFS ACLs is be available in Apache Hadoop 2.4.0, HDFS ACLs give you the ability to specify fine-grained file permissions for specific named users or named groups, not just the file’s owner and group. HDFS ACLs are modeled after POSIX ACLs , Best practice is to rely on traditional permission bits to implement most permission requirements, and define a smaller number of ACLs to augment the permission bits with a few exceptional rules. To use ACLs, first we’ll need to enable ACLs on the NameNode by adding the following configuration property to hdfs-site.xml and restarting the NameNode. Dfs.Namenode.Acls.Enabled True Most users will interact with ACLs using 2 new commands added to the HDFS CLI: setfacl and getfacl. For examples of how HDFS ACLs can help implement complex security requirements. EXAMPLE 1: G...