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   systemd-resolved.service    ( 8 )

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Описание (Description)

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 and
       MulticastDNS resolver and responder. Local applications may
       submit network name resolution requests via three interfaces:

       •   The native, fully-featured API systemd-resolved exposes on
           the bus, see org.freedesktop.resolve1(5) and
           org.freedesktop.LogControl1(5) for details. Usage of this API
           is generally recommended to clients as it is asynchronous and
           fully featured (for example, properly returns DNSSEC
           validation status and interface scope for addresses as
           necessary for supporting link-local networking).

       •   The glibc getaddrinfo(3) API as defined by RFC3493[1] and its
           related resolver functions, including gethostbyname(3). This
           API is widely supported, including beyond the Linux platform.
           In its current form it does not expose DNSSEC validation
           status information however, and is synchronous only. This API
           is backed by the glibc Name Service Switch (nss(5)). Usage of
           the glibc NSS module nss-resolve(8) is required in order to
           allow glibc's NSS resolver functions to resolve hostnames via
           systemd-resolved.

       •   Additionally, systemd-resolved provides a local DNS stub
           listener on IP address 127.0.0.53 on the local loopback
           interface. Programs issuing DNS requests directly, bypassing
           any local API may be directed to this stub, in order to
           connect them to systemd-resolved. Note however that it is
           strongly recommended that local programs use the glibc NSS or
           bus APIs instead (as described above), as various network
           resolution concepts (such as link-local addressing, or LLMNR
           Unicode domains) cannot be mapped to the unicast DNS
           protocol.

       The DNS servers contacted are determined from the global settings
       in /etc/systemd/resolved.conf, the per-link static settings in
       /etc/systemd/network/*.network files (in case
       systemd-networkd.service(8) is used), the per-link dynamic
       settings received over DHCP, information provided via
       resolvectl(1), and any DNS server information made available by
       other system services. See resolved.conf(5) and
       systemd.network(5) for details about systemd's own configuration
       files for DNS servers. To improve compatibility, /etc/resolv.conf
       is read in order to discover configured system DNS servers, but
       only if it is not a symlink to
       /run/systemd/resolve/stub-resolv.conf,
       /usr/lib/systemd/resolv.conf or /run/systemd/resolve/resolv.conf
       (see below).