DNS translates domain names to IP addresses.
Resolution process:
. Check local cache . Query recursive resolver (usually ISP or corporate) . Resolver queries root servers → TLD servers → authoritative servers . Answer cached and returned
Record types:
- A: IPv4 address
- AAAA: IPv6 address
- CNAME: Alias to another name
- MX: Mail server
- TXT: Arbitrary text (SPF, verification)
Debugging: dig example.com, nslookup example.com
Interview question: "Service can't resolve a hostname. How do you debug?" Check /etc/resolv.conf, try dig, verify DNS server is reachable.