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12.6. Troubleshooting

This section describes the most common troubleshooting scenarios related to Hadoop and Red Hat Storage integration.
Exception stating that “job.jar changed on src file system” or "job.xml changed on src file system".

This error occurs if the clocks are not synchronized across the trusted storage pool. The time in all the servers must be uniform in the trusted storage pool. It is recommended to set up a NTP (Network Time Protocol) service to keep the bricks' time synchronized, and avoid out-of-time synchronization effects.

For more information on configuring NTP, see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Migration_Planning_Guide/sect-Migration_Guide-Networking-NTP.html
While running a Hadoop job, if FileNotFoundException exception is displayed with jobtoken does not exist message:

This error occurs when the user IDs(UID) and group IDs(GID) are not consistent across the trusted storage pool. For example, user "tom" has a UID of 1002 on server1, but on server2, the user tom has a UID of 1003. The simplest and recommended approach is to leverage LDAP authentication to resolve this issue. After creating the necessary users and groups on an LDAP server, the servers within the trusted storage pool can be configured to use the LDAP server for authentication. For more information on configuring authentication, see Chapter 12. Configuring Authentication of Red Hat Enterprise Linux 6 Deployment Guide.