DNS Troubleshooting with dig: The Commands DevOps Engineers Actually Need

A surprising share of "the app is down" pages resolve to a name-resolution problem, not a broken service. The service is fine; the client can't turn a name into an address. dig is the precision tool for proving that in seconds instead of guessing. Think about it as a resolution chain, not "is DNS broken" When a name fails, work the chain: which resolver did the client ask, what did that resolver return, and does it match what authoritative DNS actually says? Most incidents live in the gap between those three. The method is boring and reliable: observe the symptom, form a hypothesis about where in the chain it breaks, test with one query, read the evidence, fix, then validate. The single most important habit: query the name from the same host and the same resolver the app uses. Running dig from your laptop proves nothing about what the pod or VM sees. The record types worth knowing You don't need all of them, but you need to recognize them: A / AAAA — name to IPv4 / IPv6 address. The usual suspect. CNAME — an alias pointing at another name. A stale or wrong CNAME sends traffic somewhere unexpected. MX — mail routing. TXT — SPF, DKIM, domain verification, and other metadata. NS — which servers are authoritative for a zone. SOA — the zone's serial and TTL defaults; the serial tells you whether a change has propagated. PTR — reverse lookup, IP back to name. The commands that actually earn their place Start with the quick answer, then get precise. dig +short api.internal.example.com +short strips everything except the answer. If it prints an IP, resolution works from this host. If it prints nothing, you have a real failure to chase. Empty output is a signal, not an error. dig api.internal.example.com A The full form. Read the status in the header: NOERROR with an ANSWER section is good; NXDOMAIN means the name genuinely doesn't exist; SERVFAIL points at a broken upstream or DNSSEC issue. Also note which SERVER answered at the bottom — that's the resolver you're actually