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Bad gateway Nginx proxy manager

Nginx Proxy Manager will try to install the Certbot DNS challenge package “certbot-dns-<provider>” after configuring SSL using DNS challenges. But however, the installation didn’t succeed and reported a few compilation errors. So we have managed to install the packages by running:

docker exec -it nginxpm_app_1 bash

Next, install many build dependencies :

apt-get install -y build-essential libssl-dev libffi-dev python3-dev cargo

Even though successfully installed the package, we couldn’t find the certificate to use for the domain. So shut down the compose and restart it so the installed build dependencies are cleared. While navigating to the admin board and trying to log in, it might give you the “Bad Gateway” error.

Solving the problem

The “Bad Gateway” error commonly means that the service is not available. And as well the Nginx Proxy Manager is not available. Since this keeps trying to install the certbot-dns-* package and failed.

The difficult part is that the error logs are not printed immediately, but after the attempt to install the certbot-dns-* package has failed. So it’s not obvious at the initial stage that there is some error installing the package.

The main common reason for 502 Gateways could be mistakes in the configuration due to incorrect HTTP / HTTPS settings or SSL not working. Couldn’t find anywhere were the following simple tips:

• While configuring the Proxy Host you still need to add the container port. Even if in case you are not exposing the ports in portainer. This didn’t work for things like Node-red or Airsonic as required 1880 and 4040 ports respectively.

• Needed to set the scheme to HTTP and NOT HTTPS. I was able to grab the SSL certificates without issue and always intended to use HTTPS on the actual site i.e. https://website.com so selected HTTPS as the scheme in the proxy host. This would not work no matter how many ways tried. Using HTTP as the scheme fixed this immediately.

• By not exposing ports to the containers in your docker stack you are not able to get into the container without using NPM. i.e. in the case of Airsonic, the only way can navigate to that container is to use website.com. I am unable as per the setup above to use servers.ip.address:4040.

• I am unable to access portainer on rafflemove.com:9000 only via my.servers.ip.address:9000

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Conclusion

The “Bad Gateway” error commonly means that the service is not available. From the Bad gateway Nginx proxy manager we have seen common reason for 502 Gateways.