NSS-RESOLVE(8)			  nss-resolve			NSS-RESOLVE(8)

NAME
       nss-resolve, libnss_resolve.so.2 - Hostname resolution via
       systemd-resolved.service

SYNOPSIS
       libnss_resolve.so.2

DESCRIPTION
       nss-resolve is a plug-in module for the GNU Name Service Switch (NSS)
       functionality of the GNU C Library (glibc) enabling it to resolve
       hostnames via the systemd-resolved(8) local network name resolution
       service. It replaces the nss-dns plug-in module that traditionally
       resolves hostnames via DNS.

       To activate the NSS module, add "resolve [!UNAVAIL=return]" to the line
       starting with "hosts:" in /etc/nsswitch.conf. Specifically, it is
       recommended to place "resolve" early in /etc/nsswitch.conf's "hosts:"
       line. It should be before the "files" entry, since systemd-resolved
       supports /etc/hosts internally, but with caching. To the contrary, it
       should be after "mymachines", to give hostnames given to local VMs and
       containers precedence over names received over DNS. Finally, we
       recommend placing "dns" somewhere after "resolve", to fall back to
       nss-dns if systemd-resolved.service is not available.

       Note that systemd-resolved will synthesize DNS resource records in a
       few cases, for example for "localhost" and the current local hostname,
       see systemd-resolved(8) for the full list. This duplicates the
       functionality of nss-myhostname(8), but it is still recommended (see
       examples below) to keep nss-myhostname configured in
       /etc/nsswitch.conf, to keep those names resolvable if systemd-resolved
       is not running.

       Please keep in mind that nss-myhostname (and nss-resolve) also resolve
       in the other direction — from locally attached IP addresses to
       hostnames. If you rely on that lookup being provided by DNS, you might
       want to order things differently.

       Communication between nss-resolve and systemd-resolved.service takes
       place via the /run/systemd/resolve/io.systemd.Resolve AF_UNIX socket.

ENVIRONMENT VARIABLES
       $SYSTEMD_NSS_RESOLVE_VALIDATE
	   Takes a boolean argument. When false, cryptographic validation of
	   resource records via DNSSEC will be disabled. This may be useful
	   for testing, or when system time is known to be unreliable.

	   Added in version 250.

       $SYSTEMD_NSS_RESOLVE_SYNTHESIZE
	   Takes a boolean argument. When false, synthetic records, e.g. for
	   the local host name, will not be returned. See section SYNTHETIC
	   RECORDS in systemd-resolved.service(8) for more information. This
	   may be useful to query the "public" resource records, independent
	   of the configuration of the local machine.

	   Added in version 250.

       $SYSTEMD_NSS_RESOLVE_CACHE
	   Takes a boolean argument. When false, the cache of previously
	   queried records will not be used by systemd-resolved(8).

	   Added in version 250.

       $SYSTEMD_NSS_RESOLVE_ZONE
	   Takes a boolean argument. When false, answers using locally
	   registered public LLMNR/mDNS resource records will not be returned.

	   Added in version 250.

       $SYSTEMD_NSS_RESOLVE_TRUST_ANCHOR
	   Takes a boolean argument. When false, answers using locally
	   configured trust anchors will not be used.

	   Added in version 250.

       $SYSTEMD_NSS_RESOLVE_NETWORK
	   Takes a boolean argument. When false, answers will be returned
	   without using the network, i.e. either from local sources or the
	   cache in systemd-resolved(8).

	   Added in version 250.

EXAMPLE
       Here is an example /etc/nsswitch.conf file that enables nss-resolve
       correctly:

	   passwd:	   files systemd
	   group:	   files [SUCCESS=merge] systemd
	   shadow:	   files systemd
	   gshadow:	   files systemd

	   hosts:	   mymachines resolve [!UNAVAIL=return] files myhostname dns
	   networks:	   files

	   protocols:	   db files
	   services:	   db files
	   ethers:	   db files
	   rpc:		   db files

	   netgroup:	   nis

SEE ALSO
       systemd(1), systemd-resolved(8), nss-systemd(8), nss-myhostname(8),
       nss-mymachines(8), nsswitch.conf(5), systemd.syntax(7)

systemd 258							NSS-RESOLVE(8)