The following is a list of environment variables that do control Geoserver behaviour.

• GEOSERVER_DATA_DIR: sets the location of you Geoserver data directory. For more details, see 4 GeoServer Data Directory documentation
• EPSG-HSQL.directory: sets the location where the EPSG database will be created and cached. Default location is the current temp directory, but this may be inappropriate on some systems because the creation requires up to 40MB and usage around 8MB (for examples, this may be an issue if your temp directory is a memory mapped disk, created for speed reasons).