# 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**](https://docs.datasentinel.io/manual/implementation/troubleshooting/selinux)

Check to see if the firewall on the Linux machine is blocking traffic on the port you are trying to connect to.