The configuration lives in /system/settings/lighttpd/ and is not overwritten if already present when lighttpd is installed or upgraded.
Template read-only configuration files are in /system/data/lighttpd/template-settings/ and correspond to the default configuration for the version of lighttpd being installed.

The default document root is /system/data/www/htdocs/.
It can be easily changed to an alternate directory, e.g. /var/www/htdocs/.
With the default configuration, access.log and error.log live in /var/log/lighttpd/.

lighttpd can be started with:
    lighttpd -f /system/settings/lighttpd/lighttpd.conf
and stopped with:
    kill $(cat /var/run/lighttpd.pid)
