openssl x509 -in ca.crt -noout -text
openssl x509 -in ca.crt -noout -enddate
openssl x509 -in ca.crt -days 3650 -out ca_new.crt -signkey ca.key
openssl req -new -out mycert.csr -keyout mycert.key
openssl x509 -req -in mycert.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out mycert.crt
(it will create mycert.crt, you can delete now the mycert.csr file)
(if needed)
openssl rsa -in mycert.key -out mycert_nopass.key
https://gist.github.com/webtobesocial/5313b0d7abc25e06c2d78f8b767d4bc3