MapR 4.0.x Documentation : Bringing Up the Cluster

The installation of software across a cluster of nodes will go more smoothly if the services have be pre-planned and each node has been validated. Referring to the cluster design developed in Planning the Cluster, ensure that each node has been prepared and meets the minimum requirements described in Preparing Each Node, and that the MapR packages have been installed on each node in accordance with the plan.

Bringing up the cluster involves setting up the administrative user, and installing a MapR license. Once these initial steps are done, the cluster is functional. You can use the MapR Control System Dashboard, or the MapR Command Line Interface, to examine nodes and activity on the cluster.

Initialization Sequence

On versions 3.1 and later of the MapR distribution for Hadoop, the script initializes the cluster automatically after a successful setup, and you can skip this process.

First, start the ZooKeeper service. It is important that all ZooKeeper instances start up, because the rest of the system cannot start unless a majority (or quorum) of ZooKeeper instances are up and running. Next, start the warden service on each node, or at least on the nodes that host the CLDB and webserver services. The warden service manages all MapR services on the node (except ZooKeeper) and helps coordinate communications. Starting the warden automatically starts the CLDB.

To bring up the cluster

  1. Start ZooKeeper on all nodes where it is installed, by issuing the following command:

    service mapr-zookeeper start

  2. Verify that the quorum has been successfully established. Issue the following command and make sure that one Zookeeper is the Leader and the rest are Followers before starting the warden:

    service mapr-zookeeper qstatus


    When the service mapr-zookeeper qstatus finds that a running ZooKeeper service is neither a leader nor a follower, the service issues an alarm that you can view with the maprcli alarm list command.

  3. Start the warden on all nodes where CLDB is installed by issuing the following command:
    service mapr-warden start

    Before continuing, wait 30 to 60 seconds for the warden to start the CLDB service. Calls to maprcli commands may fail if executed before the CLDB has started successfully.

  4. Verify that a CLDB master is running by issuing the maprcli node cldbmaster command. For example:

    # maprcli node cldbmaster
    ServerID: 4553404820491236337 HostName:

    Do not proceed until a CLDB master is active.

  5. Start the warden on all remaining nodes using the following command:
    service mapr-warden start

  6. Issue the following command to give full permission to the chosen administrative user:
    /opt/mapr/bin/maprcli acl edit -type cluster -user <user>:fc

Troubleshooting Initialization

Difficulty bringing up the cluster seems daunting, but most cluster problems are easily resolved. For the latest support tips, visit

  • Can each node connect with the others? For a list of ports that must be open, see Ports Used by MapR.
  • Is the warden running on each node? On the node, run the following command as root:

    $ service mapr-warden status
    WARDEN running as process 18732

    If the warden service is not running, check the warden log file, /opt/mapr/logs/warden.log, for clues
    To restart the warden service:

    $ service mapr-warden start
  • The ZooKeeper service is not running on one or more nodes
    • Check the warden log file for errors related to resources, such as low memory
    • Check the warden log file for errors related to user permissions
    • Check for DNS and other connectivity issues between ZooKeeper nodes
  • The MapR CLI program /opt/mapr/bin/maprcli won't run
  • Permission errors appear in the log
    • Check that MapR changes to the following files have not been overwritten by automated configuration management tools:


      Allows the mapr user to invoke commands as root


      Allows MapR services to increase limits on resources such as memory, file handles, threads and processes, and maximum priority level


      Covers permissions and ownership of raw disk devices

Before contacting MapR Support, you can collect your cluster's logs using the mapr-support-collect script.

Installing the Cluster License

MapR Hadoop requires a valid license file, even for the free M3 Community Edition.

Click on the thumbnail images to view them full-size.

Using the web-based MCS to install the license

  1. On a machine that is connected to the cluster and to the Internet, perform the following steps to open the MapR Control System and install the license:
    1. In a browser, view the MapR Control System by navigating to the node that is running the MapR Control System: https:/<webserver>/:8443
      Your computer won't have an HTTPS certificate yet, so the browser will warn you that the connection is not trustworthy. You can ignore the warning this time.
    2. The first time MapR starts, you must accept the Terms of Use and choose whether to enable the MapR Dial Home service.
    3. Log in to the MapR Control System as the administrative user you designated earlier.
      Until a license is applied, the MapR Control System dashboard might show some nodes in the amber "degraded" state. Don't worry if not all nodes are green and "healthy" at this stage.

  2. In the navigation pane of the MapR Control System, expand the System Settings Views group and click Manage Licenses to display the MapR License Management dialog.
  3. Click Add Licenses via Web
  4. If the cluster is already registered, the license is applied automatically. Otherwise, click OK to register the cluster on and follow the instructions there.

Installing a license from the command line

Use the following steps if it is not possible to connect to the cluster and the Internet at the same time.

  1. Obtain a valid license file from MapR
  2. Copy the license file to a cluster node
  3. Run the following command to add the license:
    maprcli license add [ -cluster <name> ] -license <filename> -is_file true

Verifying Cluster Status

To view cluster status using the web interface

  1. Log in to the MapR Control System.
  2. Under the Cluster group in the left pane, click Dashboard.
  3. Check the Services pane and make sure each service is running the correct number of instances, according to your cluster plan.

To view cluster status using the command line interface

  1. Log in to a cluster node
  2. Use the following command to list MapR services:
    $ maprcli service list
    name        state  logpath                        displayname
    fileserver  0      /opt/mapr/logs/mfs.log         FileServer
    webserver   0      /opt/mapr/logs/adminuiapp.log  WebServer
    cldb        0      /opt/mapr/logs/cldb.log        CLDB
    hoststats   0      /opt/mapr/logs/hoststats.log   HostStats
    $ maprcli license list
    $ maprcli disk list -host <name or IP address>

Next, start the warden on all remaining nodes using one of the following commands:

service mapr-warden start
/etc/init.d/mapr-warden start

Adding Volumes

Referring to the volume plan created in Planning the Cluster, use the MapR Control System or the maprcli command to create and mount distinct volumes to allow more granularity in specifying policy for subsets of data.

If you do not set up volumes, and instead store all data in the single volume mounted at /, it creates problems in administering data policy later as data size grows.

Next Step

Now that the MapR Hadoop cluster is up and running, the final installation step is to install Hadoop Ecosystem Components. If you will not install any Hadoop components, see Next Steps After Installation for a list of post-install considerations.




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