Fixing nginx: [emerg] BIO_new_file("/etc/nginx/ssl.crt/dhparams.pem") failed

If after an update of Nginx or because of any other reason you faced the issue with starting Nginx, which drops an error of the following kind:

Starting nginx: nginx: [emerg] BIO_new_file("/etc/nginx/ssl.crt/dhparams.pem") 
failed (SSL: error:02001002:system library:fopen:No such file or 
directory:fopen('/etc/nginx/ssl.crt/dhparams.pem','r') error:2006D080:BIO 
routines:BIO_new_file:no such file)

The error happens due to missing Diffie–Hellman (D-H) key located in /etc/nginx/ssl.crt/dhparams.pem (in your configuration its location might differ).

Here is a guide on how to solve it.

Directadmin and Custombuild

As of the moment of the publication [20.06.2015] we see they at Directadmin added these lines:

ssl_dhparam /etc/nginx/ssl.crt/dhparams.pem;

in to the following files:

/usr/local/directadmin/custombuild/configure/nginx/conf/nginx-defaults.conf
/usr/local/directadmin/custombuild/configure/nginx_reverse/conf/nginx-defaults.conf

But custombuild script does not create the file or check the existence of the file and that's the core of the issue.

A simple way to fix

Updated: 18.05.2016

The current version of Custombuild, checked with 2.0.0 (rev: 1549), has a code to make sure the correct Diffie–Hellman (D-H) key exists, and creates it if it's missing. So to fix the issue run the following commands as root:

cd /usr/local/directadmin/custombuild
./build update
./build rewrite_confs

An universal Fix

On old servers or on servers with custom installation, run the following commands as root in order to get it fixed. Of course make sure that you specified a correct path to the D-H key:

mkdir -p /etc/nginx/ssl.crt/
openssl dhparam -out /etc/nginx/ssl.crt/dhparams.pem 2048;
/etc/init.d/nginx start

Have a good day!