Note
During upgrades from versions prior to 4.20, the logging configuration file may not be migrated automatically to the new Log4j2 format - especially if the original log4j configuration file was manually customized or modified.
It is strongly recommended to verify before starting the Management Server and the Usage Server that the configuration file (e.g. log4j-cloud.xml) under /etc/cloudstack/management and /etc/cloudstack/usage respectively uses the Log4j2 format.
If the file still uses legacy Log4j (version 1) syntax or structure, manually replace or update the configuration using the default Log4j2 configuration supplied with the latest package.
Failure to update may result in missing or incomplete log generation after upgrade.