hdfs - Hadoop pseudo distributed mode - Datanode and tasktracker not starting

Question

I am running a Red Hat Enterprise Linux Server release 6.4 (Santiago) distribution with Hadoop 1.1.2 installed on it. I have made the required configurations to enable the pseudo distributed mode. But on trying to run hadoop, the datanode and tasktracker don't start.

I am not able to copy any files to hdfs.

[hduser@is-joshbloom-hadoop hadoop]$ hadoop dfs -put README.txt /input
Warning: $HADOOP_HOME is deprecated.

13/05/23 16:42:00 WARN hdfs.DFSClient: DataStreamer Exception: org.apache.hadoop.ipc.RemoteException: java.io.IOException: File /input could only be replicated to 0 nodes, instead of 1

Also after trying hadoop-daemon.sh start datanode I get the message:

starting datanode, logging to /usr/local/hadoop/libexec/../logs/hadoop-hduser-datanode-is-joshbloom-hadoop.out

same goes for tasktracker. But when I try the same command for namenode, secondarynamenode, jobtracker they are seem to be running.

namenode running as process 32933. Stop it first. 

I tried the following solutions:

1. Reformatting namenode
2. Reinstalling hadoop
3. Installing different version of hadoop (1.0.4)

None seem to work. I have followed the same installation steps on my Mac and on amazon ubuntu VM and it works perfectly.

How can I get hadoop working? Thanks!

*UPDATE**

Here is the log entry of namenode

2013-05-23 16:27:44,087 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting DataNode
STARTUP_MSG:   host = java.net.UnknownHostException: is-joshbloom-hadoop: is-joshbloom-hadoop
STARTUP_MSG:   args = []
STARTUP_MSG:   version = 1.1.2
STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1 -r 1440782; compiled by 'hortonfo' on Thu Jan 31 02:03:24 UTC 2013
************************************************************/
2013-05-23 16:27:44,382 INFO org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties
2013-05-23 16:27:44,432 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source MetricsSystem,sub=Stats registered.
2013-05-23 16:27:44,446 ERROR org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Error getting localhost name. Using 'localhost'...
java.net.UnknownHostException: is-joshbloom-hadoop: is-joshbloom-hadoop
        at java.net.InetAddress.getLocalHost(InetAddress.java:1438)
        at     org.apache.hadoop.metrics2.impl.MetricsSystemImpl.getHostname(MetricsSystemImpl.java:463)
        at org.apache.hadoop.metrics2.impl.MetricsSystemImpl.configureSystem(MetricsSystemImpl.java:394)
        at org.apache.hadoop.metrics2.impl.MetricsSystemImpl.configure(MetricsSystemImpl.java:390)
        at org.apache.hadoop.metrics2.impl.MetricsSystemImpl.start(MetricsSystemImpl.java:152)
        at org.apache.hadoop.metrics2.impl.MetricsSystemImpl.init(MetricsSystemImpl.java:133)
        at org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.init(DefaultMetricsSystem.java:40)
        at org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.initialize(DefaultMetricsSystem.java:50)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1589)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1608)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1734)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1751)
Caused by: java.net.UnknownHostException: is-joshbloom-hadoop
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:866)
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1258)
        at java.net.InetAddress.getLocalHost(InetAddress.java:1434)
        ... 11 more
2013-05-23 16:27:44,453 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled     snapshot period at 10 second(s).
2013-05-23 16:27:44,453 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: DataNode     metrics system started
2013-05-23 16:27:44,768 INFO org.apache.hadoop.metrics2.impl.MetricsSourceAdapter: MBean for source ugi registered.
2013-05-23 16:27:44,914 INFO org.apache.hadoop.util.NativeCodeLoader: Loaded the native-hadoop library
2013-05-23 16:27:45,212 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode:     java.net.UnknownHostException: is-joshbloom-hadoop: is-joshbloom-hadoop
        at java.net.InetAddress.getLocalHost(InetAddress.java:1438)
        at org.apache.hadoop.security.SecurityUtil.getLocalHostName(SecurityUtil.java:271)
        at org.apache.hadoop.security.SecurityUtil.login(SecurityUtil.java:289)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:301)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1651)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1590)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:1608)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:1734)
        at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:1751)
Caused by: java.net.UnknownHostException: is-joshbloom-hadoop
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
        at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:866)
        at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1258)
        at java.net.InetAddress.getLocalHost(InetAddress.java:1434)
        ... 8 more

2013-05-23 16:27:45,228 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down DataNode at java.net.UnknownHostException: is-joshbloom-hadoop: is-joshbloom-hadoop
************************************************************/

*UPDATE***

content of /etc/hosts

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Answer 1

Amend your /etc/hosts to include a hostname loopback mapping:

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
127.0.1.1   is-joshbloom-hadoop
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Your problem is your machine doesn't know how to resolve the hostname is-joshbloom-hadoop to a specific IP address. There are typically two places/methods resolution occurs - either via a DNS server or using a local hosts file (hosts file takes precedence).

The above amendment to your hosts file allows you machine to resolve the machine name is-joshbloom-hadoop to the IP address 127.0.1.1. The OS has an internal loopback address for the range 127.0.0.0/8, so you could name any address in here. On my Ubuntu laptop, it uses the 127.0.1.1 and i'm sure it changes between OS's, but my guess is by not using 127.0.0.1 you don't have to search for it in the localhost line if you change your machine name in future.