There are other changes coming up in Hadoop 3, which are mainly to make it easier to maintain and operate. Particularly, the command-line tools have been revamped to better suit the needs of operational teams.
Other changes
Minimum required Java version
All Hadoop JARs are now compiled to target a runtime version of Java 8. Hence, users that are still using Java 7 or lower must upgrade to Java 8.
Shell script rewrite
The Hadoop shell scripts have been rewritten to fix many long-standing bugs and include some new features.
Incompatible changes are documented in the release notes. You can find them at https://issues.apache.org/jira/browse/HADOOP-9902.
There are more details available in the documentation at https://hadoop.apache.org/docs/r3.0.0/hadoop-project-dist/hadoop-common/UnixShellGuide.html. The documentation present at https://hadoop.apache.org/docs/r3.0.0/hadoop-project-dist/hadoop-common/UnixShellAPI.html will appeal to power users, as it describes most of the new functionalities, particularly those related to extensibility.
Shaded-client JARs
The new hadoop-client-api and hadoop-client-runtime artifacts have been added, as referred to by https://issues.apache.org/jira/browse/HADOOP-11804. These artifacts shade Hadoop's dependencies into a single JAR. As a result, it avoids leaking Hadoop's dependencies onto the application's classpath.
Hadoop now also supports integration with Microsoft Azure Data Lake and Aliyun Object Storage System as an alternative for Hadoop-compatible filesystems.
