Hadoop has a native implementation for certain components, but sometimes it does not load automatically.
This is mainly the case of Hadoop 2.
The issue
The message that indicates an issue.
$ hdfs dfsadmin -printTopology
21/05/13 21:35:08 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Rack: /default-rack 192.168.8.173:9866 (datanode1.example.org) 192.168.8.174:9866 (datanode2.example.org) 192.168.8.175:9866 (datanode3.example.org)
Check all available libraries.
$ hdfs checknative -a
21/05/13 21:41:20 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Native library checking: hadoop: false zlib: false snappy: false lz4: false bzip2: false openssl: false Cannot load libcrypto.so (libcrypto.so: cannot open shared object file: No such file or directory)! 2021-05-13 21:41:20,958 INFO util.ExitUtil: Exiting with status 1: ExitException
The solution
The solution is to provide a path for the native libraries using HADOOP_OPTS variable. Note, the path must match your installation.
$ export HADOOP_OPTS="-Djava.library.path=/opt/hadoop/hadoop-2.7.3/lib/native/"
$ hdfs dfsadmin -printTopology
Rack: /default-rack 192.168.8.173:9866 (datanode1.example.org) 192.168.8.174:9866 (datanode2.example.org) 192.168.8.175:9866 (datanode3.example.org)
Ensure that HADOOP_OPTS variable is defined at login.
$ echo 'export HADOOP_OPTS="$HADOOP_OPTS -Djava.library.path=/opt/hadoop/hadoop-2.7.3/lib/native/"' | sudo tee /etc/profile.d/hadoop_opts_native.sh
Check all available libraries.
$ hdfs checknative -a
Native library checking: hadoop: true /opt/hadoop/hadoop-2.7.3/lib/native/libhadoop.so.1.0.0 zlib: true /lib/x86_64-linux-gnu/libz.so.1 snappy: true /lib/x86_64-linux-gnu/libsnappy.so.1 lz4: true revision:99 bzip2: false openssl: false Cannot load libcrypto.so (libcrypto.so: cannot open shared object file: No such file or directory)! 2021-05-13 21:43:47,019 INFO util.ExitUtil: Exiting with status 1: ExitException
Now everything is clear, so you can fix the remaining issues.