Notes
How to make a bundle from COMODO SSL certificates
$ cat COMODORSAAddTrustCA.crt COMODORSADomainValidationSecureServerCA.crt \
AddTrustExternalCARoot.crt > domain_name.ca-bundle
$ cat COMODORSAAddTrustCA.crt COMODORSADomainValidationSecureServerCA.crt \
AddTrustExternalCARoot.crt > domain_name.ca-bundle