[SOLVED] Docker container cannot resolve the subdomain defined in local machine

Docker container cannot resolve the subdomain defined in local machine

I have defined a subdomain on my local server and I want to request to subdomain from docker container but the container can not resolve the subdomain. local server uses nginx and is not a docker container.

Local nginx config

server {
    listen 80;

    root /data/www/html/sites/car/public;
    index index.php index.html index.htm;

    server_name car.localhost;

    location / {
        try_files $uri $uri/ /index.php$is_args$args;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php/php7.4-fpm.sock;
    }

    location ~ /\.ht {
        deny all;
    }
}

Local server hosts - /etc/hosts

127.0.0.1       car.localhost

Curl error in docker container

echo shell_exec("curl http://car.localhost 2>&1");
Fatal error: Uncaught Exception: [0] cURL error 6: Could not resolve host: car.localhost

Solution

Docker containers have their own hosts file and do not care what you have in your host's /etc/hosts.

If you want the container to have extra hosts you can pass that as an argument to the docker run see here: https://docs.docker.com/engine/reference/run/#managing-etchosts

Or in docker-compose file see here: https://docs.docker.com/compose/compose-file/#extra_hosts

Moreover depending on the network - the container's 127.0.0.1 might not point to the host machine. If you're using host network then it should work. But if you're using a bridge or the default config then it will be different. In this case you can use docker.internal on MAC/PC or host.docker.internal with the spceial --add-host=host.docker.internal:host-gateway on linux.