1. Put the NameNode into safe mode and save the fsimage:
   1. Put the NameNode (or active NameNode in an HA configuration) into safe mode:

      $ sudo -u hdfs hdfs dfsadmin -safemode enter

   2. Perform a saveNamespace operation:

      $ sudo -u hdfs hdfs dfsadmin -saveNamespace 

      This will result in a new fsimage being written out with no edit log entries.

   3. With the NameNode still in safe mode, shut down all services as instructed below.
2. For each component you are using, back up configuration data, databases, and other important files.
3. Shut down the Hadoop services across your entire cluster:

   for x in `cd /etc/init.d ; ls hadoop-*` ; do sudo service $x stop ; done

4. Check each host to make sure that there are no processes running as the hdfs or mapred users from root:

   # ps -aef | grep java

  Important:

Do this step when you are sure that all Hadoop services have been shut down. It is particularly important that the NameNode service is not running so that you can make a consistent backup.

To back up the HDFS metadata on the NameNode machine:

  Note:

• Cloudera recommends backing up HDFS metadata on a regular basis, as well as before a major upgrade.
• dfs.name.dir is deprecated but still works; dfs.namenode.name.dir is preferred. This example uses dfs.name.dir.

1. Find the location of your dfs.name.dir (or dfs.namenode.name.dir); for example:

   $ grep -C1 dfs.name.dir /etc/hadoop/conf/hdfs-site.xml
   
   

   You should see something like this:

   <property>
   <name>dfs.name.dir</name>
   <value>/mnt/hadoop/hdfs/name</value>

2. Back up the directory. The path inside the <value> XML element is the path to your HDFS metadata. If you see a comma-separated list of paths, there is no need to back up all of them; they store the same data. Back up the first directory, for example, by using the following commands:

   $ cd /mnt/hadoop/hdfs/name
   # tar -cvf /root/nn_backup_data.tar .
   ./
   ./current/
   ./current/fsimage
   ./current/fstime
   ./current/VERSION
   ./current/edits
   ./image/
   ./image/fsimage

     Warning:

   If you see a file containing the word lock, the NameNode is probably still running. Repeat the preceding steps, starting by shutting down the Hadoop services.

On each node in the cluster:

1. Update the alternatives, for example:

   $ sudo update-alternatives --install /etc/hadoop/conf hadoop-conf /etc/hadoop/conf.my_cluster 50

2. Verify that the operation succeeded:

   $ sudo alternatives --display hadoop-conf

  Warning:

Do not proceed before you have backed up the HDFS metadata, and the files and databases for the individual components, as instructed in the previous steps.

To uninstall Hadoop:

Run this command on each host:

On Red Hat-compatible systems:

$ sudo yum remove  bigtop-utils bigtop-jsvc bigtop-tomcat sqoop2-client hue-common solr

On SLES systems:

$ sudo zypper remove bigtop-utils bigtop-jsvc bigtop-tomcat sqoop2-client hue-common solr

On Ubuntu systems:

sudo apt-get remove bigtop-utils bigtop-jsvc bigtop-tomcat sqoop2-client hue-common solr

Remove CDH 4 Repository Files

Remove all Cloudera CDH 4 repository files. For example, on a Red Hat or similar system, remove all files in /etc/yum.repos.d that have cloudera as part of the name.

  Important:

• Before removing the files, make sure you have not added any custom entries that you want to preserve. (To preserve custom entries, back up the files before removing them.)
• Make sure you remove Impala and Search repository files, as well as the CDH repository file.

  Note:

Skip this step and go to Install CDH 5 with MRv1 if you intend to use only MRv1.

1. Install and deploy ZooKeeper.
     Important:

   Cloudera recommends that you install (or update) and start a ZooKeeper cluster before proceeding. This is a requirement if you are deploying high availability (HA) for the NameNode or JobTracker.

   Follow instructions under ZooKeeper Installation.

2. Install each type of daemon package on the appropriate systems(s), as follows.

   Where to install	Install commands
   Resource Manager host (analogous to MRv1 JobTracker) running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-yarn-resourcemanager
   SLES	sudo zypper clean --all; sudo zypper install hadoop-yarn-resourcemanager
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-yarn-resourcemanager
   NameNode host(s) running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-hdfs-namenode
   SLES	sudo zypper clean --all; sudo zypper install hadoop-hdfs-namenode
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-hdfs-namenode
   Secondary NameNode host (if used) running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-hdfs-secondarynamenode
   SLES	sudo zypper clean --all; sudo zypper install hadoop-hdfs-secondarynamenode
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-hdfs-secondarynamenode
   All cluster hosts except the Resource Manager running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-yarn-nodemanager hadoop-hdfs-datanode hadoop-mapreduce
   SLES	sudo zypper clean --all; sudo zypper clean --all; sudo zypper install hadoop-yarn-nodemanager hadoop-hdfs-datanode hadoop-mapreduce
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-yarn-nodemanager hadoop-hdfs-datanode hadoop-mapreduce
   One host in the cluster running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-mapreduce-historyserver hadoop-yarn-proxyserver
   SLES	sudo zypper clean --all; sudo zypper install hadoop-mapreduce-historyserver hadoop-yarn-proxyserver
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-mapreduce-historyserver hadoop-yarn-proxyserver
   All client hosts, running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-client
   SLES	sudo zypper clean --all; sudo zypper install hadoop-client
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-client

     Note:

   The hadoop-yarn and hadoop-hdfs packages are installed on each system automatically as dependencies of the other packages.

3. If you are installing Llama, make sure that hadoop.proxyuser.llama.hosts and hadoop.proxyuser.llama.groups are configured in your core-site.xml as follows:

    <property>
       <name>hadoop.proxyuser.llama.hosts</name>
       <value>*</value>
     </property>
     <property>
       <name>hadoop.proxyuser.llama.groups</name>
       <value>*</value>
     </property>

  Note:

Skip this step if you intend to use only YARN. If you are installing both YARN and MRv1, you can skip any packages you have already installed in Step 6a.

To install CDH 5 with MRv1:

  Note:

If you are also installing YARN, you can skip any packages you have already installed in Step 6a.

1. Install and deploy ZooKeeper.
     Important:

   Cloudera recommends that you install (or update) and start a ZooKeeper cluster before proceeding. This is a requirement if you are deploying high availability (HA) for the NameNode or JobTracker.

   Follow instructions under ZooKeeper Installation.

2. Install each type of daemon package on the appropriate systems(s), as follows.

   Where to install	Install commands
   JobTracker host running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-0.20-mapreduce-jobtracker
   SLES	sudo zypper clean --all; sudo zypper install hadoop-0.20-mapreduce-jobtracker
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-0.20-mapreduce-jobtracker
   NameNode host(s) running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-hdfs-namenode
   SLES	sudo zypper clean --all; sudo zypper install hadoop-hdfs-namenode
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-hdfs-namenode
   Secondary NameNode host (if used) running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-hdfs-secondarynamenode
   SLES	sudo zypper clean --all; sudo zypper install hadoop-hdfs-secondarynamenode
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-hdfs-secondarynamenode
   All cluster hosts except the JobTracker, NameNode, and Secondary (or Standby) NameNode hosts, running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-0.20-mapreduce-tasktracker hadoop-hdfs-datanode
   SLES	sudo zypper clean --all; sudo zypper install hadoop-0.20-mapreduce-tasktracker hadoop-hdfs-datanode
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-0.20-mapreduce-tasktracker hadoop-hdfs-datanode
   All client hosts, running:
   Red Hat/CentOS compatible	sudo yum clean all; sudo yum install hadoop-client
   SLES	sudo zypper clean --all; sudo zypper install hadoop-client
   Ubuntu or Debian	sudo apt-get update; sudo apt-get install hadoop-client

Copy over the log4j.properties file to your custom directory on each node in the cluster; for example:

$ cp /etc/hadoop/conf.empty/log4j.properties /etc/hadoop/conf.my_cluster/log4j.properties

1. Install the JournalNode daemons on each of the machines where they will run.

   To install JournalNode on Red Hat-compatible systems:

   $ sudo yum install hadoop-hdfs-journalnode

   To install JournalNode on Ubuntu and Debian systems:

   $ sudo apt-get install hadoop-hdfs-journalnode 

   To install JournalNode on SLES systems:

   $ sudo zypper install hadoop-hdfs-journalnode

2. Start the JournalNode daemons on each of the machines where they will run:

   sudo service hadoop-hdfs-journalnode start 

Wait for the daemons to start before proceeding to the next step.

  Important:

The JournalNodes must be up and running CDH 5 before you proceed.

  Note:

What you do in this step differs depending on whether you are upgrading an HDFS HA deployment using Quorum-based storage, or a non-HA deployment using a secondary NameNode. (If you have an HDFS HA deployment using NFS storage, do not proceed; you cannot upgrade that configuration to CDH 5. Unconfigure your NFS shared storage configuration before you attempt to upgrade.)

• For an HA deployment, do sub-steps 1, 2, and 3.
• For a non-HA deployment, do sub-steps 1, 3, and 4.

1. To upgrade the HDFS metadata, run the following command on the NameNode. If HA is enabled, do this on the active NameNode only, and make sure the JournalNodes have been upgraded to CDH 5 and are up and running before you run the command.

   $ sudo service hadoop-hdfs-namenode -upgrade

     Important:

   In an HDFS HA deployment, it is critically important that you do this on only one NameNode.

   You can watch the progress of the upgrade by running:

   $ sudo tail -f /var/log/hadoop-hdfs/hadoop-hdfs-namenode-<hostname>.log 

   Look for a line that confirms the upgrade is complete, such as: /var/lib/hadoop-hdfs/cache/hadoop/dfs/<name> is complete

     Note:

   The NameNode upgrade process can take a while depending on how many files you have.

2. Do this step only in an HA configuration. Otherwise skip to starting up the DataNodes.

   Wait for NameNode to exit safe mode, and then re-start the standby NameNode.

   • If Kerberos is enabled:

     $ kinit -kt /path/to/hdfs.keytab hdfs/<fully.qualified.domain.name@YOUR-REALM.COM> && hdfs namenode -bootstrapStandby

     $ sudo service hadoop-hdfs-namenode start

   • If Kerberos is not enabled:

     $ sudo -u hdfs hdfs namenode -bootstrapStandby
     $ sudo service hadoop-hdfs-namenode start

   For more information about the haadmin -failover command, see Administering an HDFS High Availability Cluster.

3. Start up the DataNodes:

   On each DataNode:

   $ sudo service hadoop-hdfs-datanode start

4. Do this step only in a non-HA configuration. Otherwise skip to starting YARN or MRv1.

   Wait for NameNode to exit safe mode, and then start the Secondary NameNode.

   1. To check that the NameNode has exited safe mode, look for messages in the log file, or the NameNode's web interface, that say "...no longer in safe mode."
   2. To start the Secondary NameNode (if used), enter the following command on the Secondary NameNode host:

      $ sudo service hadoop-hdfs-secondarynamenode start 

   3. To complete the cluster upgrade, follow the remaining steps below.

You are now ready to start and test MRv1 or YARN.

Start MapReduce with YARN

  Important:

Make sure you are not trying to run MRv1 and YARN on the same set of nodes at the same time. This is not supported; it will degrade your performance and may result in an unstable MapReduce cluster deployment. Steps 10a and 10b are mutually exclusive.

After you have verified HDFS is operating correctly, you are ready to start YARN. First, create directories and set the correct permissions.

For more information see Deploying MapReduce v2 (YARN) on a Cluster.

Create a history directory and set permissions; for example:

sudo -u hdfs hadoop fs -mkdir /user/history
sudo -u hdfs hadoop fs -chmod -R 1777 /user/history
sudo -u hdfs hadoop fs -chown yarn /user/history

Create the /var/log/hadoop-yarn directory and set ownership:

$ sudo -u hdfs hadoop fs -mkdir /var/log/hadoop-yarn
$ sudo -u hdfs hadoop fs -chown yarn:mapred /var/log/hadoop-yarn

You need to create this directory because it is the parent of /var/log/hadoop-yarn/apps which is explicitly configured in the yarn-site.xml.

Verify the directory structure, ownership, and permissions:

$ sudo -u hdfs hadoop fs -ls -R /

You should see:

drwxrwxrwt   - hdfs supergroup          0 2012-04-19 14:31 /tmp
drwxr-xr-x   - hdfs supergroup          0 2012-05-31 10:26 /user
drwxrwxrwt   - yarn supergroup          0 2012-04-19 14:31 /user/history
drwxr-xr-x   - hdfs   supergroup        0 2012-05-31 15:31 /var
drwxr-xr-x   - hdfs   supergroup        0 2012-05-31 15:31 /var/log
drwxr-xr-x   - yarn   mapred            0 2012-05-31 15:31 /var/log/hadoop-yarn

To start YARN, start the ResourceManager and NodeManager services:

  Note:

Make sure you always start ResourceManager before starting NodeManager services.

On the ResourceManager system:

$ sudo service hadoop-yarn-resourcemanager start

On each NodeManager system (typically the same ones where DataNode service runs):

$ sudo service hadoop-yarn-nodemanager start

To start the MapReduce JobHistory Server

On the MapReduce JobHistory Server system:

$ sudo service hadoop-mapreduce-historyserver start

For each user who will be submitting MapReduce jobs using MapReduce v2 (YARN), or running Pig, Hive, or Sqoop in a YARN installation, make sure that the HADOOP_MAPRED_HOME environment variable is set correctly as follows:

$ export HADOOP_MAPRED_HOME=/usr/lib/hadoop-mapreduce

Verify basic cluster operation for YARN.

At this point your cluster is upgraded and ready to run jobs. Before running your production jobs, verify basic cluster operation by running an example from the Apache Hadoop web site.

  Note:

For important configuration information, see Deploying MapReduce v2 (YARN) on a Cluster.

1. Create a home directory on HDFS for the user who will be running the job (for example, joe):

   $ sudo -u hdfs hadoop fs -mkdir /user/joe
   $ sudo -u hdfs hadoop fs -chown joe /user/joe 

   Do the following steps as the user joe.

2. Make a directory in HDFS called input and copy some XML files into it by running the following commands in pseudo-distributed mode:

   $ hadoop fs -mkdir input
   $ hadoop fs -put /etc/hadoop/conf/*.xml input
   $ hadoop fs -ls input
   Found 3 items:
   -rw-r--r--   1 joe supergroup       1348 2012-02-13 12:21 input/core-site.xml
   -rw-r--r--   1 joe supergroup       1913 2012-02-13 12:21 input/hdfs-site.xml
   -rw-r--r--   1 joe supergroup       1001 2012-02-13 12:21 input/mapred-site.xml

3. Set HADOOP_MAPRED_HOME for user joe:

   $ export HADOOP_MAPRED_HOME=/usr/lib/hadoop-mapreduce 

4. Run an example Hadoop job to grep with a regular expression in your input data.

   $ hadoop jar /usr/lib/hadoop-mapreduce/hadoop-mapreduce-examples.jar grep input output23 'dfs[a-z.]+'

5. After the job completes, you can find the output in the HDFS directory named output23 because you specified that output directory to Hadoop.

   $ hadoop fs -ls
   Found 2 items
   drwxr-xr-x   - joe supergroup  0 2009-08-18 18:36 /user/joe/input
   drwxr-xr-x   - joe supergroup  0 2009-08-18 18:38 /user/joe/output23

   You can see that there is a new directory called output23.

6. List the output files.

   $ hadoop fs -ls output23
   Found 2 items
   drwxr-xr-x  -  joe supergroup     0 2009-02-25 10:33   /user/joe/output23/_SUCCESS
   -rw-r--r--  1  joe supergroup  1068 2009-02-25 10:33   /user/joe/output23/part-r-00000

7. Read the results in the output file.

   $ hadoop fs -cat output23/part-r-00000 | head
   1    dfs.safemode.min.datanodes
   1    dfs.safemode.extension
   1    dfs.replication
   1    dfs.permissions.enabled
   1    dfs.namenode.name.dir
   1    dfs.namenode.checkpoint.dir
   1    dfs.datanode.data.dir

You have now confirmed your cluster is successfully running CDH 5.

  Important:

If you have client hosts, make sure you also update them to CDH 5, and upgrade the components running on those clients as well.

Start MapReduce (MRv1)

  Important:

Make sure you are not trying to run MRv1 and YARN on the same set of nodes at the same time. This is not supported; it will degrade your performance and may result in an unstable MapReduce cluster deployment. Steps 9a and 9b are mutually exclusive.

After you have verified HDFS is operating correctly, you are ready to start MapReduce. On each TaskTracker system:

$ sudo service hadoop-0.20-mapreduce-tasktracker start

On the JobTracker system:

$ sudo service hadoop-0.20-mapreduce-jobtracker start

Verify that the JobTracker and TaskTracker started properly.

$ sudo jps | grep Tracker

If the permissions of directories are not configured correctly, the JobTracker and TaskTracker processes start and immediately fail. If this happens, check the JobTracker and TaskTracker logs and set the permissions correctly.

  Important:

For each user who will be submitting MapReduce jobs using MapReduce v1 (MRv1), or running Pig, Hive, or Sqoop in an MRv1 installation, set the HADOOP_MAPRED_HOME environment variable as follows:

$ export HADOOP_MAPRED_HOME=/usr/lib/hadoop-0.20-mapreduce

Verify basic cluster operation for MRv1.

At this point your cluster is upgraded and ready to run jobs. Before running your production jobs, verify basic cluster operation by running an example from the Apache Hadoop web site.

1. Create a home directory on HDFS for the user who will be running the job (for example, joe):

   $ sudo -u hdfs hadoop fs -mkdir /user/joe
   $ sudo -u hdfs hadoop fs -chown joe /user/joe

   Do the following steps as the user joe.

2. Make a directory in HDFS called input and copy some XML files into it by running the following commands:

   $ hadoop fs -mkdir input
   $ hadoop fs -put /etc/hadoop/conf/*.xml input
   $ hadoop fs -ls input
   Found 3 items:
   -rw-r--r--   1 joe supergroup       1348 2012-02-13 12:21 input/core-site.xml
   -rw-r--r--   1 joe supergroup       1913 2012-02-13 12:21 input/hdfs-site.xml
   -rw-r--r--   1 joe supergroup       1001 2012-02-13 12:21 input/mapred-site.xml

3. Set HADOOP_MAPRED_HOME for user joe:

   $ export HADOOP_MAPRED_HOME=/usr/lib/hadoop-0.20-mapreduce/

5. Run an example Hadoop job to grep with a regular expression in your input data.

   $ /usr/bin/hadoop jar /usr/lib/hadoop-0.20-mapreduce/hadoop-examples.jar grep input output 'dfs[a-z.]+'

6. After the job completes, you can find the output in the HDFS directory named output because you specified that output directory to Hadoop.

   $ hadoop fs -ls
   Found 2 items
   drwxr-xr-x   - joe supergroup  0 2009-08-18 18:36 /user/joe/input
   drwxr-xr-x   - joe supergroup  0 2009-08-18 18:38 /user/joe/output

   You can see that there is a new directory called output.

7. List the output files.

   $ hadoop fs -ls output
   Found 2 items
   drwxr-xr-x  -  joe supergroup     0 2009-02-25 10:33   /user/joe/output/_logs
   -rw-r--r--  1  joe supergroup  1068 2009-02-25 10:33   /user/joe/output/part-00000
   -rw-r--r-   1  joe supergroup     0 2009-02-25 10:33   /user/joe/output/_SUCCESS

8. Read the results in the output file; for example:

   $ hadoop fs -cat output/part-00000 | head
   1       dfs.datanode.data.dir
   1       dfs.namenode.checkpoint.dir
   1       dfs.namenode.name.dir
   1       dfs.replication
   1       dfs.safemode.extension
   1       dfs.safemode.min.datanodes

   You have now confirmed your cluster is successfully running CDH 5.

     Important:

   If you have client hosts, make sure you also update them to CDH 5, and upgrade the components running on those clients as well.

For security reasons Cloudera strongly recommends you set the sticky bit on directories if you have not already done so.

The sticky bit prevents anyone except the superuser, directory owner, or file owner from deleting or moving the files within a directory. (Setting the sticky bit for a file has no effect.) Do this for directories such as /tmp. (For instructions on creating /tmp and setting its permissions, see these instructions).

To install the CDH 5 components, see the following sections:

• Crunch. For more information, see "Crunch Installation" in this guide.
• Flume. For more information, see "Flume Installation" in this guide.
• HBase. For more information, see "HBase Installation" in this guide.
• HCatalog. For more information, see "Installing and Using HCatalog" in this guide.
• Hive. For more information, see "Hive Installation" in this guide.
• Hue. For more information, see "Hue Installation" in this guide.
• Impala. For more information, see "About Impala" in this guide.
• Llama. For more information, see "Llama Installation" in this guide.
• Mahout. For more information, see "Mahout Installation" in this guide.
• Oozie. For more information, see "Oozie Installation" in this guide.
• Pig. For more information, see "Pig Installation" in this guide.
• Search. For more information, see "Search Installation" in this guide.
• Sentry. For more information, see "Sentry Installation" in this guide.
• Snappy. For more information, see "Snappy Installation" in this guide.
• Spark. For more information, see "Spark Installation" in this guide.
• Sqoop 1. For more information, see "Sqoop Installation" in this guide.
• Sqoop 2. For more information, see "Sqoop 2 Installation" in this guide.
• Whirr. For more information, see "Whirr Installation" in this guide.
• ZooKeeper. For more information, "ZooKeeper Installation" in this guide.

  Important:

During uninstall, the package manager renames any configuration files you have modified from <file> to <file>.rpmsave. During re-install, the package manager creates a new <file> with applicable defaults. You are responsible for applying any changes captured in the original CDH 4 configuration file to the new CDH 5 configuration file. In the case of Ubuntu and Debian upgrades, a file will not be installed if there is already a version of that file on the system, and you will be prompted to resolve conflicts; for details, see Automatic handling of configuration files by dpkg.

For example, if you have modified your CDH 4 zoo.cfg configuration file (/etc/zookeeper.dist/zoo.cfg), RPM uninstall and re-install (using yum remove) renames and preserves a copy of your modified zoo.cfg as /etc/zookeeper.dist/zoo.cfg.rpmsave. You should compare this to the new /etc/zookeeper/conf/zoo.cfg and resolve any differences that should be carried forward (typically where you have changed property value defaults). Do this for each component you upgrade to CDH 5.

To finalize the HDFS metadata upgrade you began earlier in this procedure, proceed as follows:

1. Make sure you are satisfied that the CDH 5 upgrade has succeeded and everything is running smoothly. This could take a matter of days, or even weeks.
     Warning:

   Do not proceed until you are sure you are satisfied with the new deployment. Once you have finalized the HDFS metadata, you cannot revert to an earlier version of HDFS.

     Note:

   If you need to restart the NameNode during this period (after having begun the upgrade process, but before you've run finalizeUpgrade) simply restart your NameNode without the -upgrade option.

2. Finalize the HDFS metadata upgrade: use one of the following commands, depending on whether Kerberos is enabled (see Configuring Hadoop Security in CDH 5).
     Important:

   In an HDFS HA deployment, make sure that both the NameNodes and all of the JournalNodes are up and functioning normally before you proceed.

   • If Kerberos is enabled:

     $ kinit -kt /path/to/hdfs.keytab hdfs/<fully.qualified.domain.name@YOUR-REALM.COM> && hdfs dfsadmin -finalizeUpgrade

   • If Kerberos is not enabled:

     $ sudo -u hdfs hdfs dfsadmin -finalizeUpgrade

     Note:

   After the metadata upgrade completes, the previous/ and blocksBeingWritten/ directories in the DataNodes' data directories aren't cleared until the DataNodes are restarted.