RESOLVED.CONF(5)

NAME
resolved.conf, resolved.conf.d - Network Name Resolution configuration files

SYNOPSIS

/etc/systemd/resolved.conf

/etc/systemd/resolved.conf.d/*.conf

/run/systemd/resolved.conf.d/*.conf

/usr/lib/systemd/resolved.conf.d/*.conf

DESCRIPTION

These configuration files control local DNS and LLMNR name resolving.

CONFIGURATION DIRECTORIES AND PRECEDENCE

Default configuration is defined during compilation, so a configuration file is only needed when it is necessary to deviate from those defaults. By default the configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. This file can be edited to create local overrides.

When packages need to customize the configuration, they can install configuration snippets in /usr/lib/systemd/*.conf.d/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. The main configuration file is read before any of the configuration directories, and has the lowest precedence; entries in a file in any configuration directory override entries in the single configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of which of the subdirectories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name takes precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the files.

To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file.

OPTIONS

DNS=
    A space separated list of IPv4 and IPv6 addresses to be used as system DNS servers. DNS requests are sent to one of the listed DNS servers in parallel to any per-interface DNS servers acquired from systemd-networkd.service(8). For compatibility reasons, if set to the empty list the DNS servers listed in /etc/resolv.conf are used, if any are configured there. This setting defaults to the empty list.

FallbackDNS=
    A space separated list of IPv4 and IPv6 addresses to be used as the fallback DNS servers. Any per-interface DNS servers obtained from systemd-networkd.service(8) take precedence over this setting, as do any servers set via DNS= above or /etc/resolv.conf. This setting is hence only used if no other DNS server information is known. If this option is not given, a compiled-in list of DNS servers is used instead.

LLMNR=
    Takes a boolean argument or "resolve". Controls Link-Local Multicast Name Resolution support (RFC 4794[1]) on the local host. If true enables full LLMNR responder and resolver support. If false disable both. If set to "resolve" only resolving support is enabled, but responding is disabled. Note that systemd-networkd.service(8) also maintains per-interface LLMNR settings. LLMNR will be enabled on an interface only if the per-interface and the global setting is on.

SEE ALSO

systemd(1), systemd-resolved.service(8), systemd-networkd.service(8), resolv.conf(4)

NOTES

1.  RFC 4794
    https://tools.ietf.org/html/rfc4795