How to create a CSR (Certificate Signing Request) in Linux using OpenSSL

Before you can purchase or create your own self signed SSL certificate, you must first create a CSR (Certificate Signing Request) and a Private Key. These two files much be created simultaneously or the resulting SSL certificate will not work.

As root, Run the following command:

openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout SUB.DOMAIN.TLD.key -out SUB.DOMAIN.TLD.csr

Or try this to auto-complete filling the questions:

openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout SUB.DOMAIN.TLD.key -out SUB.DOMAIN.TLD.csr -subj="/C=US/ST=Texas/L=Austin/O=How To Web Host.com/OU=Development/CN=SUB.DOMAIN.TLD"

Finally, Use this script to create certs as you need them

#! /bin/bash

if [ -z "$1" ]
then
	echo "ERROR: No domain specified."
	echo "You must run this command followed by the sub.domain.tld you wish to create certs for."
	echo "Example: ./mkcert.sh cisco.eflashcards.org"
else
	openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout $1.key -out $1.csr -subj "/C=US/ST=Texas/L=Austin/O=How To Web Host.com/OU=Development/CN=$1"
	echo "Add the following lines to the /etc/apache2/sites-available/$1.conf file"
	echo " "
        echo "SSLCertificateFile  `pwd`/$1.csr"
        echo "SSLCertificateKeyFile  `pwd`/$1.key"
fi

Generating a 2048 bit RSA private key
............+++
.......................+++
writing new private key to 'sub.domain.com.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [XX]:US
State or Province Name (full name) []:State
Locality Name (eg, city) [Default City]:City
Organization Name (eg, company) [Default Company Ltd]:Business Name or Domain.com
Organizational Unit Name (eg, section) []:optional
Common Name (eg, your name or your server's hostname) []:sub.domain.com
Email Address []:optional

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:Enter
An optional company name []:Enter

With the above command, both the CSR (sub.domain.com.csr) and Private Key (sub.domain.com.key) files are created.