Troubleshooting

Cloudera Manager raises a timezone mismatch alert when the OS clock files disagree with the timezone CM expects. This post walks through the three key files to check and how to align them.

A quick two-step check to confirm the Kerberos key version number in your KDC database matches the value stored in a local keytab file. Mismatched KVNO values are a common cause of authentication failures in Hadoop and other Kerberized services.

Hue does not provide a built-in UI option to remove user accounts. This workaround uses the Hue Django shell to delete one or more users directly from the database, with a clear caveat that the process is unsupported.

A quick reference for calculating the exact timeout window before Hadoop marks a Datanode as dead, based on the heartbeat and recheck-interval settings.

When hostname -f returns a short name instead of a fully qualified domain name, the issue usually traces back to the HOSTNAME variable in /etc/sysconfig/network or a misconfigured /etc/hosts entry. Understanding the difference between the gethostname and gethostbyname system calls makes the fix straightforward.

Specific JDK 1.8.0 builds (u40, u45, u91, u92) are known to break SPNEGO authentication and Hadoop web interfaces. This post documents the affected versions, the symptoms, and the recommended downgrade path.