ACLs stands for Access Control Lists and it gives finer level access control over files. Without ACLs permissions are controlled at owner, group and others levels only.
To use ACLs in HDFS, we need to set dfs.namenode.acls.enabled to true as part of hdfs-site.xml.
We can use
hadoop fs -setfacl to set ACL at file or directory level.
hadoop fs -getfacl can be used to get details about ACL on a file or a directory.
First, let us see examples at the file level, then directory level and then deleting ACLs.