# Error message: “502 Bad Gateway” An error message `502: Bad Gateway’ is displayed when attempting to access the user interface`. To ensure that all components are operational, execute “status\_datasentinel” while logged in as the owner of datasentinel. ``` $ status_datasentinel datasentinel_backend.service loaded active running Datasentinel backend API datasentinel_dispatcher.service loaded active running Datasentinel Agentless datasentinel_grafana.service loaded active running Datasentinel grafana daemon datasentinel_influxdb.service loaded active running InfluxDB service datasentinel_postgresql.service loaded active running Datasentinel PostgreSQL instance nginx.service loaded active running A high performance web server and a reverse proxy server ``` A 502 error from **nginx** indicates that the proxy server was unable to establish a connection to a local component on another port, either grafana or the backend. The most common reason is a firewall issue, especially [**SELINUX**](/manual/implementation/troubleshooting/selinux.md) Check to see if the firewall on the Linux machine is blocking traffic on the port you are trying to connect to. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.datasentinel.io/manual/implementation/troubleshooting/error-message-502-bad-gateway.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.