...
- Shutdown Bamboo
Edit the log4j.properties file under <bamboo-installation-directory>/atlassian-bamboo/WEB-INF/classes and change the line:
log4j.appender.filelog=com.atlassian.bamboo.log.BambooRollingFileAppender
To:
log4j.appender.filelog=org.apache.log4j.DailyRollingFileAppender
Then add an additional:
log4j.appender.filelog.DatePattern='.'yyyy-MM-dd-a