How to view logs in Hadoop?

To view Hadoop logs, you can follow these steps:

1. Log in to the node server running Hadoop.
2. Navigate to the log directory of Hadoop, which is typically located in the subdirectory of the installation directory called logs.
3. Under this directory, you can find log files for various components such as NameNode, DataNode, and ResourceManager.
4. Open the necessary log file in a text editor to view its contents.

In addition, Hadoop also provides a convenient log viewing tool called Hadoop Log Aggregator. By configuring the Hadoop Log Aggregator, logs from various nodes can be aggregated onto one server for easier viewing and analysis. To use the Hadoop Log Aggregator, follow these steps:

1. Locate the relevant log aggregator configuration options in the Hadoop configuration files, such as yarn.log-aggregation-enable and yarn.log-aggregation.retain-seconds.
2. Adjust the values of these configuration settings as needed.
3. Restart the Hadoop cluster.
4. On a server within the Hadoop cluster, use the Hadoop command line tools to run the following command to view aggregated logs:
5. Please provide the application id when viewing Hadoop logs.
6. The is the identifier for the application you want to view, which can be found on the web interface of the Hadoop Resource Manager.

The above method allows for easy viewing of Hadoop log information.