CI "curl: (6) Could not resolve host" - DNS Failure on Runner

By Kaveh Alemi·Latchkey

curl exit code 6 is CURLE_COULDNT_RESOLVE_HOST - the name never resolved, so no connection was even attempted. On a runner this is usually a transient resolver blip that clears on retry.

What this error means

A curl download or API call fails immediately with curl: (6) Could not resolve host: <name>. Nothing connected because DNS returned nothing. The same step typically passes on a re-run with no change.

curl: (6) Could not resolve host: api.github.com

Common causes

Transient DNS resolver blip

The upstream resolver briefly failed or timed out. DNS is best-effort UDP, so a momentary blip yields a hard "could not resolve" that clears on retry.

Missing or broken resolver configuration

A container with an empty or wrong /etc/resolv.conf, or a runner whose DNS was not yet configured, cannot resolve any name until it is fixed.

How to fix it

Confirm resolution and config

getent hosts api.github.com || nslookup api.github.com
cat /etc/resolv.conf

Retry, then fix config if it persists

1. Re-run the step or wrap curl in a bounded retry - a one-off blip clears.
2. If it persists, set a working nameserver in /etc/resolv.conf.
3. For containers, pass --dns or fix the daemon DNS settings.

How to prevent it

• Wrap network steps in bounded retry-with-backoff (curl --retry).
• Ensure runners and containers ship a valid resolver config.
• Cache or mirror dependencies to cut external DNS lookups.

Frequently asked questions

Related guides

References

• GitHub Actions documentation