generate crt into pem

openssl x509 -in domain.crt -out domain.der -outform DER openssl x509 -in domain.der -inform DER -out domain.pem -outform PEM

refer: http://kbeezie.com/view/free-ssl-with-nginx/2/

convert from p12 to pem format

openssl pkcs12 -in file.p12 -out file.pem

reference : http://www.openssl.org/docs/apps/pkcs12.html