certificate_authority: unique_subject = no
"openssl ca" is keeping track of all generated certificates in its DB. If we try to regenerate a certificate that was already generated, openssl ca fails with :
ERROR:There is already a certificate for /C=XX/ST=(State,)/O=Company/CN=ca-shellinabox/emailAddress=xx@example.com
Changing "unique_subject" to no removes thie ERROR.