I am going to setup https for my site. However, my site uses wildcard dns record. There are about 300,000 SLDs(automatically generated by site system).
So I am wondering if Let’s Encrypt supports wildcard dns record? I am using Linode Server, using Centos system.
Yes, wildcard DNS records work fine. The notion of a “wildcard” is purely implemented at your DNS server. From Let’s Encrypt’s perspective, it just looks up a DNS name and gets an answer.
You may be able to work out a rate limit exception from Let’s Encrypt – i don’t know – but honestly, paying $100 a year for a wildcard certificate from another CA may be your best option.