The Gentics CMS writes several log files for different tasks in /cms/logs. An overview of all logfiles can be found in the Gentics CMS documentation.
Gentics Mesh uses Logback and logs errors to stderr and other messages to stdout by default, but this can be configured in the config/logback.xml file. More details on this can be found in the Gentics Mesh documentation.
Gentics Portal | php uses Laravel logging, and it’s default path is in the portal/storage/logs/laravel.log. Other logging settings can be configured via the portal/config/logging.php and via its environment variables or .env file.
Gentics Portal | java also uses Logback for logging and therefore the configuration options for its config/logback.xml are the same as the ones mentioned above for Gentics Mesh.