Last night, I installed my Comodo Positive SSL certificate for Pixel Jumble. This went relatively smoothly. I did run into one problem though; figuring out in which order to consolidate the certificates into one .pem file. I checked Comodo’s documentation, however the names it says the root and intermediate are called weren’t what I had. However, through some digging online and trial and error, I found the correct combination. That combination is:
www_domain_com.crt, COMODORSADomainValidationSecureServerCA.crt, COMODORSAAddTrustCA.crt, and AddTrustExternalCARoot.crt
After combining the certificates into one .pem file in this order, it worked perfectly. Nginx was able to start just fine with no errors, and I was able to get SSL implemented on Pixel Jumble.
Combining the certificates in this order should also work with any web server or configuration.
Source: Ben’s Pro Tips