No datanode running in hadoop 2.9.2 - hadoop

Question

I'm very new to hadoop, so I've started following the hadoop 2.9.2 getting started. When I run the command
bin/hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.9.2.jar grep input output 'dfs[a-z.]+'
it returns a success, but when I look at the output/part-r-00000.txt file, which is meant to show the result, it is empty, even though the input directory contains the .xml files of etc/hadoop as it is supposed to.
I've started the whole process over and over again, reading all the logs, in order to understand where the error might be. Anyway, when I run the bin/hdfs namenode -format, it shows me this error:
ERROR common.Util: Syntax error in URI file://path to temp_directory/dfs/name. Please check hdfs configuration.
java.net.URISyntaxException: Illegal character in authority at index 7: file://path to temp_directory/dfs/name
at java.base/java.net.URI$Parser.fail(URI.java:2915)
at java.base/java.net.URI$Parser.parseAuthority(URI.java:3249)
at java.base/java.net.URI$Parser.parseHierarchical(URI.java:3160)
at java.base/java.net.URI$Parser.parse(URI.java:3116)
at java.base/java.net.URI.<init>(URI.java:600)
at org.apache.hadoop.hdfs.server.common.Util.stringAsURI(Util.java:49)
at org.apache.hadoop.hdfs.server.common.Util.stringCollectionAsURIs(Util.java:99)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getStorageDirs(FSNamesystem.java:1466)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getNamespaceEditsDirs(FSNamesystem.java:1511)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getNamespaceEditsDirs(FSNamesystem.java:1480)
at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:1137)
at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1614)
at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1741)
and also this occurs when I run bin/hdfs dfs -put etc/hadoop input:
WARN hdfs.DataStreamer: DataStreamer Exception
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /user/federico/input/hadoop/capacity-scheduler.xml._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 0 datanode(s) running and no node(s) are excluded in this operation.
it seems pretty clear that there are no datanodes running. So, assumed this situation, how can I initialize a datanode to make things work, and how do I know if my datanode is running as it is expected to?
EDIT: I've tried to follow some suggestion fro different users experiencing a similar problem and tihs error came out:
WARN org.apache.hadoop.hdfs.server.datanode.checker.StorageLocationChecker: Exception checking StorageLocation [DISK]file:/dfs/data
java.io.FileNotFoundException: File file:/dfs/data does not exist
and thus the datanode creation fails. How do I deal with it?

Answer 1

Please update you hdfs-site.xml as follows where dfs.datanode.data.dir value should be set as per your expectations. You can find this file in /etc/hadoop under Hadoop installation directory.
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
<property>
<name>dfs.datanode.data.dir</name>
<value>/Users/myname/data/hdfs/data</value>
</property>
</configuration>
Use similar paths for linux as /home/myname/data/hdfs/data