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in networkd man page, the search domains are used to handle single-label names:

The domains without the prefix are called "search domains" and are first used as search suffixes for extending single-label host names (host names containing no dots) to become fully qualified domain names (FQDNs). If a single-label host name is resolved on this interface, each of the specified search domains are appended to it in turn, converting it into a fully qualified domain name, until one of them may be successfully resolved.

Both "search" and "routing-only" domains are used for routing of DNS queries: look-ups for host names ending in those domains (hence also single label names, if any "search domains" are listed), are routed to the DNS servers configured for this interface.

I wonder if a single-label name lookup request is handled by LLMNR or by the specified dns severs or both?

Solaroi Zeng
  • 105

1 Answers1

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A single-label name is only handled by LLMNR, if solved.

If not solved, each of the list of words in Domains=:

Domains=domainA.example domainB.example ~example

is added at the end of the single-label and an attempt to resolve it is done. If it gets resolved at any trial, that is the end, if not resolved, try with the next word.

To resolve, different name resolution resources might be used: Avahi, resolved, LLMNR, or (usually at last) several DNS servers.