DNS: A records and TTL

DNS turns a name like shiqi.si into an IP address. You manage the records at your registrar (or whichever DNS host the domain points to).

The records you need for one server

• A: name → IPv4 address. @ means the bare domain itself, www means www.shiqi.si.
• AAAA: the same for IPv6. Only add it if the server really has a public IPv6 address.
• CNAME: name → another name. www can be a CNAME to the bare domain instead of a second A record. The bare domain itself cannot be a CNAME.

Remove any parking-page A record on @ first; two A records on the same name mean visitors are split between them.

TTL

TTL (time to live) is in seconds: how long resolvers may cache the answer. 300 is five minutes. Use a short TTL while you are still moving things around, and a longer one (3600 or more) once the address is stable.

"Not yet propagated" just means caches around the world still hold the old answer (or none). New records usually show up within minutes; changes can take as long as the old TTL.

Checking

dig +short shiqi.si          # the A record your resolver sees
dig +short shiqi.si @1.1.1.1 # ask a specific public resolver
dig shiqi.si ANY +noall +answer

On a Mac without dig, nslookup shiqi.si works too.

Why HTTPS waits for DNS

Let's Encrypt proves you control a domain by connecting to it. Until the A record points at your server, the certificate request fails, so a web server with automatic HTTPS will keep retrying until DNS is right. See Automatic HTTPS with Caddy.