How to set up a 301 redirect from www to non-www in nginx for all pages?

Question

Nginx

Good afternoon. Please tell me, in fact, the redirect from www to without www works for me, but the 301 code does not give back, but it needs to give it back.
Here he wrote:

server {
    if ($host = www.dev.site.ru) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    if ($host = dev.site.ru) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    server_name dev.site.ru www.dev.site.ru;
    listen 80;
    return 404; # managed by Certbot

}

The whole file looks like this:

server {
    root /var/www/dev.site.ru/public_html/;
    server_name dev.site.ru www.dev.site.ru;
    index index.php;
    location ~* \.(js|css|png|jpg|jpeg|gif|ico|html)$ {
        access_log    off;
        log_not_found    off;
        expires max;
    }
    location / {
            # add_header Access-Control-Allow-Origin *;
            try_files $uri $uri/ /index.php?$query_string;
    }
    location ~ \.php$ {
        try_files $uri = 404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php/php7.4-fpm.sock;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }

    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/dev.site.ru/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/dev.site.ru/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

    include /var/www/dev.site.ru/public_html/nginx.conf;
}
server {
    if ($host = www.dev.site.ru) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    if ($host = dev.site.ru) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    server_name dev.site.ru www.dev.site.ru;
    listen 80;
    return 404; # managed by Certbot

}

If I add at the end:

server {
server_name www.dev.site.ru;
return 301 https://dev.site.ru$request_uri;
}

then error: nginx warn conflicting server name on 0.0.0.0 80 ignored

Answer 1

You need three sections server{}
One for port 80 with server_name dev.site.ru www.dev.site.ru ; and return 301 https://dev.site.ru$request_uri ;
One for port 443 with server_name www.dev.site.ru ;, certificates and return 301 https://dev.site.ru$request_uri ;
Another one at 443 from server_name dev.site.ru ; and the main part of your config.
In your case, the added section intersects by port (80) and the server_name(www.dev.site.ru) part with the section added by certbot.