All you need is to write your logs to stdout in container. All containers in kubernetes are listened by another container fluentd for STDOUT.
Simply put consolappender to the config and logs will appear in
<configuration>
<!--Daily rolling file appender-->
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
<File>target/surefire-reports/blah-logback.log</File>
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<FileNamePattern>blah-logback.log.%d{yyyy-MM-dd}</FileNamePattern>
</rollingPolicy>
<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
<Pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%-10.10thread] %logger{36} - %msg%n%rEx</Pattern>
<immediateFlush>true</immediateFlush>
</encoder>
</appender>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%msg%n</pattern>
</encoder>
</appender>
<root level="INFO">
<appender-ref ref="FILE"/>
<appender-ref ref="STDOUT"/>
</root>
</configuration>