when running tomcat, the slf4j library isn't correctly initialized, this is not a problem by itself since it simply turns off logging completely for the components that use slf, however if the logging output is needed for a component it would be better to provide the simple logger.
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
when I put the necessary jar into the war, the log output becomes this:
16 [NullIdDescriptorMonitor.verifyId] INFO org.apache.sshd.common.util.SecurityUtils - Trying to register BouncyCastle as a JCE provider
511 [NullIdDescriptorMonitor.verifyId] INFO org.apache.sshd.common.util.SecurityUtils - Registration succeeded
so this is used by the sshd module in the default installation.
Alternatively, the binding for jdk14 logging or log4j could be used (which ever is more fitting for the rest of jenkins).