http://www.togaware.com/linux/survivor/Renew_SSL.html

Generate key

openssl genrsa -out file.key 1024
openssl req -new -key file.key -out file.csr

Renew a self-signed cert

openssl x509 -req -days 365 -in file.csr -signkey file.key -out file.crt
cat file.key file.crt > file.pem