[HADOOP-8008] Document how to change the default loglevels

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: documentation
• Labels: newbie
• Target Version/s: 2.0.0-alpha
• Assignee: Tomohiko Kinebuchi
• Reporter: Eli Collins
• Created: 31/Jan/12 04:30
• Updated: 20/May/12 07:55

Description

The hadoop.root.logger defined in log4j.properties is only used by applications. The scripts (bin and daemons) always set it to HADOOP_ROOT_LOGGER or "INFO,console" so the installed log4j.properties appears to be ignored. The wiki doesn't cover this:
http://wiki.apache.org/hadoop/HowToConfigure

We should update the cluster setup docs to indicate how the loglevel is configured and also add a comment in log4j.properties that the hadoop.root.logger defined there is not used by Hadoop itself, that HADOOP_ROOT_LOGGER must be set. This is relevant for commands and daemons, though the latter also has daemonlog (http://hadoop.apache.org/common/docs/current/commands_manual.html#daemonlog).