Step 7: Configure Secure HDFS

When following the instructions in this section to configure the properties in the hdfs-site.xml file, keep the following important guidelines in mind:

  • The properties for each daemon (NameNode, Secondary NameNode, and DataNode) must specify both the HDFS and HTTP principals, as well as the path to the HDFS keytab file.
  • The Kerberos principals for the NameNode, Secondary NameNode, and DataNode are configured in the hdfs-site.xml file. The same hdfs-site.xml file with all three of these principals must be installed on every host machine in the cluster. That is, it is not sufficient to have the NameNode principal configured on the NameNode host machine only. This is because, for example, the DataNode must know the principal name of the NameNode in order to send heartbeats to it. Kerberos authentication is bi-directional.
  • The special string _HOST in the properties is replaced at run-time by the fully-qualified domain name of the host machine where the daemon is running. This requires that reverse DNS is properly working on all the hosts configured this way. You may use _HOST only as the entirety of the second component of a principal name. For example, hdfs/_HOST@YOUR-REALM.COM is valid, but hdfs._HOST@YOUR-REALM.COM and hdfs/_HOST.example.com@YOUR-REALM.COM are not.
  • When performing the _HOST substitution for the Kerberos principal names, the NameNode determines its own hostname based on the configured value of fs.default.name, whereas the DataNodes determine their hostnames based on the result of reverse DNS resolution on the DataNode hosts. Likewise, the JobTracker uses the configured value of mapred.job.tracker to determine its hostname whereas the TaskTrackers, like the DataNodes, use reverse DNS.
  • The dfs.datanode.address and dfs.datanode.http.address port numbers for the DataNode must be below 1024, because this provides part of the security mechanism to make it impossible for a user to run a map task which impersonates a DataNode. The port numbers for the NameNode and Secondary NameNode can be anything you want, but the default port numbers are good ones to use.

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To configure secure HDFS

Add the following properties to the hdfs-site.xml file on every machine in the cluster. Replace these example values shown below with the correct settings for your site: path to the HDFS keytab, YOUR-REALM.COM, fully qualified domain name of NN, and fully qualified domain name of 2NN

<!-- General HDFS security config -->
<property>
  <name>dfs.block.access.token.enable</name>
  <value>true</value>
</property>

<!-- NameNode security config -->
<property>
  <name>dfs.namenode.keytab.file</name>
  <value>/etc/hadoop/conf/hdfs.keytab</value> <!-- path to the HDFS keytab -->
</property>
<property>
  <name>dfs.namenode.kerberos.principal</name>
  <value>hdfs/_HOST@YOUR-REALM.COM</value>
</property>
<property>
  <name>dfs.namenode.kerberos.internal.spnego.principal</name>
  <value>HTTP/_HOST@YOUR-REALM.COM</value>
</property>

<!-- Secondary NameNode security config -->
<property>
  <name>dfs.secondary.namenode.keytab.file</name>
  <value>/etc/hadoop/conf/hdfs.keytab</value> <!-- path to the HDFS keytab -->
</property>
<property>
  <name>dfs.secondary.namenode.kerberos.principal</name>
  <value>hdfs/_HOST@YOUR-REALM.COM</value>
</property>
<property>
  <name>dfs.secondary.namenode.kerberos.internal.spnego.principal</name>
  <value>HTTP/_HOST@YOUR-REALM.COM</value>
</property>

<!-- DataNode security config -->
<property>
  <name>dfs.datanode.data.dir.perm</name>
  <value>700</value> 
</property>
<property>
  <name>dfs.datanode.address</name>
  <value>0.0.0.0:1004</value>
</property>
<property>
  <name>dfs.datanode.http.address</name>
  <value>0.0.0.0:1006</value>
</property>
<property>
  <name>dfs.datanode.keytab.file</name>
  <value>/etc/hadoop/conf/hdfs.keytab</value> <!-- path to the HDFS keytab -->
</property>
<property>
  <name>dfs.datanode.kerberos.principal</name>
  <value>hdfs/_HOST@YOUR-REALM.COM</value>
</property>

<!-- Web Authentication config -->
<property>
  <name>dfs.web.authentication.kerberos.principal</name>
  <value>HTTP/_HOST@YOUR_REALM</value>
 </property>

To enable SSL for HDFS

Add the following property to hdfs-site.xml on every machine in your cluster. 
<property>
<name>dfs.http.policy</name>
<value>HTTPS_ONLY</value>
</property>