If you have trouble identifying which certificates you need, here the more detailed explanation:
You usually have a list of certificates in the PEM file you pass to lighttpd. The first certificate usually has a "Subject" pointing to your server name (CN), like: "Subject: CN=lighttpd.net". It also has a "Issuer" attribute (like "C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"). The issuer certificate needs a "Subject" matching that "Issuer", and should be the second certificate in the PEM file (unless it already is the root CA, in which case it is usually omitted).
@ocsptool@ will always use the first certificate in a file and ignore the others, so you can use the normal PEM file you pass to lighttpd as argument after @--load-cert@, but you need to extract the issuer certificate if you don't have it in a separate file. The following @awk@ script extracts the second PEM block from a file:
