nginx.conf.sigil

The nginx.conf.sigil file is used to configure the nginx server for an application. The default template can be found here. Dokku uses a tool named sigil to generate the nginx configuration based on the template provided.

Validation

A custom nginx.conf.sigil is pre-validated at the start of every deploy, immediately after it is extracted from the source tree and before the build phase runs. Pre-validation renders the template via sigil with the same parameters used at deploy time, wraps the rendered config in a minimal events/http scaffold, and runs nginx -t against the result. The deploy is aborted if either the sigil render or the nginx -t check fails, so build work is not wasted on a syntactically invalid template. When no app listeners exist yet (typical for first deploys), pre-validation injects a placeholder 127.0.0.1:5000 listener for DOKKU_APP_WEB_LISTENERS so that the rendered upstream block has a static server entry and nginx -t does not bail out on "host not found in upstream".

Pre-validation is skipped when the proxy type is not nginx or when disable-custom-config is set to true for the app.