The following custom configurations are kept during the upgrade and rollback process:

Java Agent on Linux:

path: <zero agent path>/java/javaagent/ver***/conf/*.xml

Machine Agent:

path: <zero agent path>/zeroagent/agents/machineagent/conf/logging/log4j.xml
path: <zero agent path>/zeroagent/agents/machineagent/conf/controller-info.xml
path: <zero agent path>/zeroagent/agents/machineagent/monitors

For details on the Machine Agent configurations, see Configure the Machine Agent.