The log4j.properties files <GATEWAY_HOME>/conf can be used to change the granularity of the logging done by Knox. The Knox server must be restarted in order for these changes to take effect. There are various useful loggers pre-populated in that file but they are commented out.
log4j.logger.org.apache.hadoop.gateway=DEBUG # Use this logger to increase the debugging of Apache Knox itself. log4j.logger.org.apache.shiro=DEBUG # Use this logger to increase the debugging of Apache Shiro. log4j.logger.org.apache.http=DEBUG # Use this logger to increase the debugging of Apache HTTP components. log4j.logger.org.apache.http.client=DEBUG # Use this logger to increase the debugging of Apache HTTP client component. log4j.logger.org.apache.http.headers=DEBUG # Use this logger to increase the debugging of Apache HTTP header. log4j.logger.org.apache.http.wire=DEBUG # Use this logger to increase the debugging of Apache HTTP wire traffic.