How to resolve the issue when the namenode is not shown in jps after starting Hadoop.
If you do not see the namenode process appear in the output of the jps command when starting Hadoop, it may be due to a failed namenode startup. You can try the following methods to resolve this issue:
- Check Hadoop log files: Examine Hadoop log files, especially the namenode log file, to identify any error messages and try to resolve them.
- Check the configuration files: Ensure that the configuration files for Hadoop (such as core-site.xml, hdfs-site.xml, etc.) are set up correctly, especially for the namenode-related configurations.
- Check the port status to ensure that the ports required by the namenode (such as dfs.namenode.rpc-address, dfs.namenode.http-address, etc.) are not being used by other processes.
- Try rebooting the entire Hadoop cluster to see if it resolves the issue.
- Check hardware resources: Ensure that the host where the namenode is located has enough hardware resources (memory, CPU, etc.) to support the running of the namenode process.
If the above methods still do not resolve the issue, it may be necessary to conduct further investigation or try reinstalling Hadoop to fix the problem.