Temporary failure in name resolution (EAI_AGAIN)
The resolver received no usable answer at all, rather than a negative one, so the problem is the path to the resolver rather than the record. An empty or wrong /etc/resolv.conf, a container that inherited a host only nameserver, and UDP 53 dropped by a firewall all look like this while everything else works.
Quick fix
Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.
# Which resolver is in use, and does it answer directly?
resolvectl status | head -20
cat /etc/resolv.conf
dig @1.1.1.1 example.com +short
# Containers take resolv.conf from the daemon, not from your shell
docker run --rm alpine cat /etc/resolv.conf
docker run --dns 1.1.1.1 --rm alpine getent hosts example.com
# systemd-resolved: the stub file should point at 127.0.0.53
ls -l /etc/resolv.conf
sudo systemctl restart systemd-resolved
# Firewalls: 53 needs both UDP and TCP, and 853 if DNS over TLS is set
sudo nc -vzu 1.1.1.1 53How to diagnose DNS errors
DNS errors are best diagnosed by working down the delegation chain: root, TLD, authoritative nameserver, then the record itself. The most common mistake is testing only through your local resolver, which caches both good and bad answers and hides where the failure actually is. NXDOMAIN means the name definitively does not exist; SERVFAIL means the resolver could not get a valid answer, which is usually a DNSSEC or authoritative-server problem, not a typo.
If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.
- Query the authoritative nameserver directly, bypassing all caches:
dig @ns1.example.com example.com A. If that answers correctly, you have a caching or propagation issue, not a records issue. - Trace the full delegation with
dig +trace example.com. This shows exactly which level of the hierarchy stops returning answers. - Distinguish NXDOMAIN from SERVFAIL from timeout. They have three entirely different causes. Check the
status:line in dig output. - For SERVFAIL, test with DNSSEC validation disabled:
dig +cd example.com. If that succeeds, the problem is a broken DNSSEC chain, often after a key rollover. - Check TTLs before declaring propagation broken. A record with a 24-hour TTL genuinely will not update for resolvers that cached it, and there is no way to force them.
Tools worth reaching for
dig +tracedig @authoritative-nsdig +cd (DNSSEC bypass)kdigresolvectl status
Authoritative references
Primary documentation for this error, worth reading before applying any fix in production.
Related DNS errors
- Bad Gateway - DNS resolutionReverse proxy cannot resolve the upstream server's hostname to an IP address.
- DNS cache poisoning detectedDNS resolver returned suspicious results, possibly indicating cache poisoning attack.
- DNS lookup timeoutDNS query took too long to complete, often due to slow or unresponsive DNS servers.
- DNS NXDOMAINDomain name does not exist in DNS, the queried domain is not registered or configured.
- DNS resolution failedThe domain name could not be resolved to an IP address. DNS server may be unreachable or the…
- DNS server unreachableConfigured DNS servers are not responding, preventing domain name resolution.
- DNS: CNAME loop detectedA CNAME record points to another CNAME that eventually points back, creating a circular…
- DNS: SERVFAILThe DNS server failed to complete the query. The authoritative server may be down, DNSSEC…
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Something missing or wrong?
This entry is maintained by hand. If the fix is out of date, incomplete, or you have a better one, email a correction and it will be reviewed.