Debugging notes from building CentOS Hadoop2 images

24 Apr 2014

This documents the process I have followed to create a Sahara cluster using CentOS based Hadoop2 images.

Creating the Image

The images were created on a RHEL6 machine with SELinux disabled by changing /etc/selinx/config to contain SELINUX=disabled. This machine has access to the Optional channel as well as EPEL.

The trunk of sahara-image-elements was used for image creation. The last commit of the repo used was 28a76fd0c0e7b5431c26728fe60185d79d65eff6. The last commit of the diskimage-builder repo used by sahara-image-elements was 6b2a78f3abdcb7133ded96324f30907739f8f855. I ran the following command to create the image for testing:

$ sudo -p hdp -i centos -v 2 -d

I realize the -i centos isn’t strictly needed, but I wanted to be thorough when testing the image creation.

NOTE There is an issue currently being resolved with diskimage-builder when creating CentOS images without the base element, for more information see bug 1308224.

Loading the Image

I am using the tip of Devstack trunk, installed as per the “Quick Start” instructions. This is the local.conf file I am using:

All of the following step were performed using the standard Horizon dashboard interface in the Demo project. I have registered a newly created keypair that was created with $ ssh-keygen -t rsa.

  1. Create Images

    Imported using the Create Image button from the project’s Images tab. QCOW2 format selected, no architecture, minimum disk, or minimum ram were entered.

  2. Register Image

    Image registered using the Register Image button from the Sahara > Image Registry tab. The user name ec2-user was entered.

  3. Create Node Group Templates

    Templates created using the Create Template button from the Sahara > Node Group Templates tab.

    For this cluster I have created 2 node group templates, a “master” node, and a “worker” node.

    Both nodes use the m1.small OpenStack flavor, ephemeral drive storage location, and the public floating ip pool.


    The worker node processes selected were; DATANODE, HDFS_CLIENT, PIG, MAPREDUCE2_CLIENT, NODEMANAGER, and OOZIE_CLIENT.

  4. Create Cluster Template

    Template created using the Create Template button from the Sahara > Cluster Templates tab.

    The template was created with 1 master node and 2 worker nodes.

  5. Launching the Cluster

    From the Sahara > Cluster Templates tab, I used the Launch Cluster button from the freshly created template. I used the previously mentioned image as the base, the registered keypair, and the private network for management.

    At this point the cluster will stay in the Spawning status for a few minutes, moving into the Waiting state. In never seems to go past Waiting.

Debug Notes

I can log into the instances using ssh and the keypair, but only as root. If I try to ssh in as ec2-user I get disconnected immediately. This is resolved by setting SELinux to Permissive on the instance.

All the nodes produce the same errors at the end of boot:

Full boot log for master node

Full boot log for worker node

The JAVA_HOME error is being addressed in review 89515.

The Ambari server error seems to be based around the fact that these instances do not have access to the internet and the ambari-server setup command seems to want to download a jdk image by default. If I run the setup from an ssh shell I am able to select the jdk contained in /opt/jdk1.6.0_31 and the setup will complete.

The worker nodes appear to have an improper server hostname in their /etc/ambari-agent/conf/ambari-agent.ini. They all contain localhost for the server hostname, this may be due to the server not configuring properly but, if the value is changed to the IP for the configured server then their agents run properly.

Even with all the ambari processing running the cluster does not leave Waiting status. There may be additional steps required to get the cluster into a working state. This is still being investigated.


  • 2014-04-25

Attaching the log files for the ambari-agent from the master node, and the sahara log from the host machine. The file /var/log/ambari-agent/ambari-agent.out was empty as was the /var/log/ambari-server directory.



  • 2014-05-01

Setting the proper floating ip configuration in Sahara allowed me to get past the Waiting status. This involved ensuring that the following were set use_neutron=true, use_floating_ips=true, and use_namespaces=false.

In the version of devstack I am using these are mostly preconfigured. In the past I had been able to use the namespaces setting but apparently that is not working from my devstack.

With these settings in place my cluster was able to move to the Preparing status.

At this point I was able to ssh into the master node and run ambari-server setup as root. I chose the default options with the exception of the JDK. For that I chose the Custom JDK option and selected /opt/jdk1.6.0_31 directory. This allowed the ambari-server to finish setting up.

Next I ssh’d to the worker nodes and updated /etc/ambari-agent/conf/ambari-agent.ini to have the proper server address. All the workers had localhost as their server addresses.

With both of these fixes in place the cluster started moving along once again. It became stopped in the Configuring status.

Looking at the Sahara log files these is an exception happening with an attempt to get a repo file from the public internet. Here is the full exception stack:




  • 2014-05-08

Made more progress in getting the cluster to configure itself with the following changes:

Changed to using the cloud-user for logging into the instances as updates to sahara-image-elements have changed the default user.

Commented out the install_rpms call in the provision_ambari method in sahara/plugins/hdp/ New code looks like:

    def provision_ambari(self, ambari_info, cluster_spec):
        global_config = cluster_spec.configurations['global']
        jdk_path = global_config.get('java64_home')

Added a security group rule to allow ingress traffic on 8080 from

The next problem issue was the Nagios server installation which failed multiple times. Fortunately it seems that the cluster doesn’t necessarily need it for creation. Removing the NAGIOS_SERVER from the master node allowed the cluster creation to make it further.

After all the tasks were initialized the next step in the plugin is to install the Hadoop Swift integration. This attempts to download an rpm from Amazon S3 which fails in disconnected mode. The Hadoop Swift integration rpm is loaded on the image during creation from sahara-image-elemnts, it can be found in /opt/hdp-local-repos/hadoop-swift/. It is not installed by default.

  • 2014-05-09

I have added 2 patches to work around the remote installs. In the case of the rpm installed during provision_ambari, I have added a small piece to detect if the rpm is already installed. For the Hadoop Swift integration piece I have added a patch to detect the local version of the rpm and install that instead of hitting the internet.

Here is a summary of the patches.

With these patches in place the cluster has progressed to the Starting status.