systemd-resolved.service, systemd-resolved — Network Name Resolution manager
systemd-resolved is a system service that provides network name resolution to local
applications. It implements a caching and validating DNS/DNSSEC stub resolver, as well as an LLMNR resolver and
responder. In addition it maintains the
/run/systemd/resolve/resolv.conf file for
compatibility with traditional Linux programs. This file may be symlinked from
The glibc NSS module nss-resolve(8) is required to permit glibc's NSS resolver functions to resolve host names via systemd-resolved.
The DNS servers contacted are determined from the global
per-link static settings in
and the per-link dynamic settings received over DHCP. See
for details. To improve compatibility,
/etc/resolv.conf is read in order to discover
configured system DNS servers, but only if it is not a symlink
/run/systemd/resolve/resolv.conf (see above).
systemd-resolved synthesizes DNS RRs for the following cases:
The local, configured hostname is resolved to all locally configured IP addresses ordered by their scope, or — if none are configured — the IPv4 address 127.0.0.2 (which is on the local loopback) and the IPv6 address ::1 (which is the local host).
The hostname "
localhost" (as well as any hostname ending in
.localdomain" or equal to "
resolved to the IP addresses 127.0.0.1 and ::1.
The hostname "
resolved to all current default routing gateway addresses,
ordered by their metric. This assigns a stable hostname to the
current gateway, useful for referencing it independently of the
current network configuration state.
The mappings defined in
/etc/hosts are resolved to their configured
addresses and back.
Lookup requests are routed to the available DNS servers and LLMNR interfaces according to the following rules:
Lookups for the special hostname
localhost" are never routed to the
network. (A few other, special domains are handled the same way.)
Single-label names are routed to all local
interfaces capable of IP multicasting, using the LLMNR
protocol. Lookups for IPv4 addresses are only sent via LLMNR on
IPv4, and lookups for IPv6 addresses are only sent via LLMNR on
IPv6. Lookups for the locally configured host name and the
gateway" host name are never routed to
Multi-label names are routed to all local interfaces that have a DNS sever configured, plus the globally configured DNS server if there is one. Address lookups from the link-local address range are never routed to DNS.
If lookups are routed to multiple interfaces, the first successful response is returned (thus effectively merging the lookup zones on all matching interfaces). If the lookup failed on all interfaces, the last failing response is returned.
Routing of lookups may be influenced by configuring per-interface domain names. See systemd.network(5) for details. Lookups for a hostname ending in one of the per-interface domains are exclusively routed to the matching interfaces.
/run/systemd/resolve/resolv.conf should not be used directly by applications,
but only through a symlink from
See the resolved D-Bus API
Documentation for information about the APIs