How do I print hadoop properties in command line

Question

 I only find the way to set a property by Hadoop dfsadmin -D xx=yy ,

but how do I find the value of a specific property xx in command line?

Answer 1

You can dump Hadoop config by running:

$ hadoop org.apache.hadoop.conf.Configuration

You can use GenericOptionsParser to load Hadoop's setting to Configuration-typed object and iterate its properties. Here is an example demonstrating this approach through a utility class (Configured).

public class ConfigPrinter extends Configured implements Tool {
    static {
        // by default core-site.xml is already added
        // loading "hdfs-site.xml" from classpath
        Configuration.addDefaultResource("hdfs-site.xml");
        Configuration.addDefaultResource("mapred-site.xml");
    }

    @Override
    public int run(String[] strings) throws Exception {
        Configuration config =  this.getConf();
        for (Map.Entry<String, String> entry : config) {
            System.out.println(entry.getKey() + " = " + entry.getValue());
        }
        return 0;
    }

    public static void main(String[] args) throws Exception {
        ToolRunner.run(new ConfigPrinter(), args);
    }
}

I hope this answer helps :)