diff --git a/man/systemd-resolved.service.xml b/man/systemd-resolved.service.xml index 32512fd6275..8f3494e36b0 100644 --- a/man/systemd-resolved.service.xml +++ b/man/systemd-resolved.service.xml @@ -183,7 +183,9 @@ domain configured, in which case the query is sent to all of them in parallel). In case of single-label names, when search domains are defined, the same logic applies, except - that the name is first suffixed by each of the search domains in turn. + that the name is first suffixed by each of the search domains in turn. Note that this search logic + doesn't apply to any names with at least one dot. Also see the discussion about compatiblity with + the traditional glibc resolver below. If a query does not match any configured routing domain (either per-link or global), it is sent to all DNS servers that are configured on links with the DefaultRoute= @@ -216,6 +218,63 @@ for information about the D-Bus APIs systemd-resolved provides. + + Compatibility with the traditional glibc stub resolver + + This section provides a short summary of differences in the stub resolver implemented by + nss-resolve8 together + with systemd-resolved and the tranditional stub resolver implemented in + nss-dns8. + + + Some names are always resolved internally (see Synthetic Records above). Traditionally + they would be resolved by nss-files, and only if provided in + /etc/hosts. + + Single-label names are not resolved for A and AAAA records using unicast DNS (unless + overriden with ResolveUnicastSingleLabel=, see + resolved.conf5). + This is similar to the option being set in + resolv.conf5. + + + Search domains are not used for suffixing of multi-label names. + (Search domains are nevertheless used for lookup routing, for names that were + originally specified as single-label or multi-label.) Any name with at least one dot is always + interpreted as a FQDN. nss-dns would resolve names both as relative (using search + domains) and absolute FQDN names. Some names would be resolved as relative first, and after that query + has failed, as absolute, while other names would be resolved in opposite order. The + ndots option in /etc/resolv.conf was used to control how many + dots the name needs to have to be resolved as relative first. This stub resolver does not implement + this at all: multi-label names are only resolved as FQDNs. (There are currently more than 1500 + top-level domain names defined, and new ones are added regularly, often using "attractive" names that + are also likely to be used locally. Not looking up multi-label names in this fashion avoids fragility + in both directions: a valid global name could be obscured by a local name, and resolution of a relative + local name could suddenly break when a new top-level domain is created, or when a new subdomain of a + top-level domain in registered. Resolving any given name as either relative or absolute avoids this + ambiguity.) + + This resolver has a notion of the special .local domain used for + MulticastDNS, and will not route queries with that suffix to unicast DNS servers unless explicitly + configured, see above. Also, reverse lookups for link-local addresses are not sent to unicast DNS + servers. + + This resolver reads and caches /etc/hosts internally. (In other + words, nss-resolve replaces nss-files in addition to + nss-dns). Entries in /etc/hosts have highest priority. + + + This resolver also implements LLMNR and MulticastDNS in addition to the classic unicast + DNS protocol, and will resolve single-label names using LLMNR (when enabled) and names ending in + .local using MulticastDNS (when enabled). + + Environment variables $LOCALDOMAIN and + $RES_OPTIONS described in + resolv.conf5 are not + supported currently. + + + <filename>/etc/resolv.conf</filename> @@ -302,7 +361,6 @@ synchronous way. -