Host Reachable Through cURL but Cannot Be Resolved by nslookup
Recently I was doing some weird shit with docker and docker compose that required a weird DNS setup. While debugging a problem with DNS resolution in nginx I came across a strange issue: I could reach a host by curl and ping but wasn’t able to resolve it using nslookup and dig.
A quick Google search wasn’t really helpful so I decided to run strace on both
tools and see if there’s an obvious difference in how they handle name resolution.
After looking at the trace I finally spotted the difference: curl was opening
/etc/hosts and dig wasn’t!
Turns out extra_hosts
is adding hostnames to the /etc/hosts file which isn’t checked by the DNS tools or
nginx resolver.
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