Try in this possible dirs if you can find the files to find out:
For Apache:
/etc/apache2/sites-enabled
And look for your/srv/www/redmine/public
For Nginx
/etc/nginx/conf.d
or/etc/nginx/sites-enabled
or/opt/nginx/conf/conf.d
or something like that
That would do it under any standard setup, but you know every master has its own recipes.
If the app is up and running, another easy option if there is no complex situation to find out which services are running 'ps aux', do it while browsing the app.