Make a copy of openssl.cnf:

<code>
cd /var/tmp
mkdir mySSL
cp /usr/share/ssl/openssl.cnf /var/tmp/mySSL/myssl.cnf

</code>

Insert SAN names into myssl.cnf.
Edit the custom openssl.cnf file (/var/tmp/mySSL/myssl.cnf) and add the following information to the end of the file:
<file>  
   [ req_ext ]
   subjectAltName    = @alt_names
   
   [ alt_names ]
   DNS.1    = <FQDN>
   DNS.2    = <host.domain1>
   DNS.3    = <host.domain2>
   DNS.4    = <host.domain3>
   ...
   DNS.x    = <host.domainx>
</file>

For example:  
<file>
  [ req_ext ]
   subjectAltName    = @alt_names
   
   [ alt_names ]
   DNS.1    = www.example.com
   DNS.2    = test.example.com
   DNS.3    = mail.example.com
   DNS.4    = www.example.net
</file>

Create the certificate request:

<code>
openssl req -new -nodes -newkey rsa:2048 -config /var/tmp/mySSL/myssl.cnf -reqexts req_ext -keyout /var/tmp/mySSL/www.example.com.key -out /var/tmp/mySSL/www.example.com.csr
</code>