Don't Panic

If users report a problem, always start by dividing it: Verify if the problems exists at all.

Also take a note when the problem occurred (ideally when the user had it and when you reproduced it), so you can reduce the amount of log data you have to analyze.

Once it's sure there is a problem, narrow it down. Never ever forget about basics like cables, network connectivity, DHCP servers, DNS, and especially firewalls and proxies.

Once it seems clear where the problem lies, read the log files. Carefully. Twice. Again.

Karaf log file: karaf.log

Karaf only uses one log file: karaf.log.

In Windows installations you find it in the data\log\ subdirectory of the Karaf installation directory, i.e. usually C:\Program Files\apache-karaf\data\log resp. /var/lib/apache-karaf/data/log/karaf.log.

Configuring logging details like log levels

Log levels can be changed editing Karaf's config file org.ops4j.pax.logging.cfg, which directly configures Karaf's Log4J.

For instance, to extend the logging of the login services to DEBUG, add these lines:

# all login parts
log4j.logger.org.clazzes.login=DEBUG

# LDAP/ADS login parts
log4j.logger.org.clazzes.login.ldap=DEBUG

This configuration file also allows to configure the name of the log file, the rotation pattern, and so on.