An optional configuration file uses TOML and by default should be saved at ~/.opendexd/opendex.conf on Linux or AppData\Local\OpenDEX\opendex.conf on Windows. Run opendexd at least once for this folder to be created. The opendexd repository contains an up-to-date sample-opendex.conf which serves as template for creating opendex.conf. It is possible to overwrite the default data directory by launching opendexd with opendexd --opendexdir=/path/to/custom/opendexdir.
The precedence order in which configuration option values are applied is as follows (high to low):
Option given on the command line
Option read from the config file
Option default value (as seen in the output of opendexd --help)