'\" t
.TH "SYSTEMD\-RESOLVED\&.SERVICE" "8" "" "systemd 230" "systemd-resolved.service"
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.SH "NAME"
systemd-resolved.service, systemd-resolved \- Network Name Resolution manager
.SH "SYNOPSIS"
.PP
systemd\-resolved\&.service
.PP
/lib/systemd/systemd\-resolved
.SH "DESCRIPTION"
.PP
\fBsystemd\-resolved\fR
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
/etc/resolv\&.conf\&.
.PP
The glibc NSS module
\fBnss-resolve\fR(8)
is required to permit glibc\*(Aqs NSS resolver functions to resolve host names via
\fBsystemd\-resolved\fR\&.
.PP
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, and the per\-link dynamic settings received over DHCP\&. See
\fBresolved.conf\fR(5)
and
\fBsystemd.network\fR(5)
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 to
/run/systemd/resolve/resolv\&.conf
(see above)\&.
.PP
\fBsystemd\-resolved\fR
synthesizes DNS RRs for the following cases:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The local, configured hostname is resolved to all locally configured IP addresses ordered by their scope, or \(em if none are configured \(em the IPv4 address 127\&.0\&.0\&.2 (which is on the local loopback) and the IPv6 address ::1 (which is the local host)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The hostnames
"localhost"
and
"localhost\&.localdomain"
(as well as any hostname ending in
"\&.localhost"
or
"\&.localhost\&.localdomain") are resolved to the IP addresses 127\&.0\&.0\&.1 and ::1\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The hostname
"gateway"
is 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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The mappings defined in
/etc/hosts
are resolved to their configured addresses and back\&.
.RE
.PP
Lookup requests are routed to the available DNS servers and LLMNR interfaces according to the following rules:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Lookups for the special hostname
"localhost"
are never routed to the network\&. (A few other, special domains are handled the same way\&.)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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 LLMNR\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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\&.
.RE
.PP
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\&.
.PP
Routing of lookups may be influenced by configuring per\-interface domain names\&. See
\fBsystemd.network\fR(5)
for details\&. Lookups for a hostname ending in one of the per\-interface domains are exclusively routed to the matching interfaces\&.
.PP
Note that
/run/systemd/resolve/resolv\&.conf
should not be used directly by applications, but only through a symlink from
/etc/resolv\&.conf\&.
.PP
See the
\m[blue]\fBresolved D\-Bus API Documentation\fR\m[]\&\s-2\u[1]\d\s+2
for information about the APIs
systemd\-resolved
provides\&.
.SH "SIGNALS"
.PP
\fBSIGUSR1\fR
.RS 4
Upon reception of the SIGUSR1 process signal
\fBsystemd\-resolved\fR
will dump the contents of all DNS resource record caches it maintains into the system logs\&.
.RE
.PP
\fBSIGUSR2\fR
.RS 4
Upon reception of the SIGUSR2 process signal
\fBsystemd\-resolved\fR
will flush all caches it maintains\&. Note that it should normally not be necessary to request this explicitly \(en except for debugging purposes \(en as
\fBsystemd\-resolved\fR
flushes the caches automatically anyway any time the host\*(Aqs network configuration changes\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBresolved.conf\fR(5),
\fBdnssec-trust-anchors.d\fR(5),
\fBnss-resolve\fR(8),
\fBsystemd-resolve\fR(1),
\fBresolv.conf\fR(5),
\fBhosts\fR(5),
\fBsystemd.network\fR(5),
\fBsystemd-networkd.service\fR(8)
.SH "NOTES"
.IP " 1." 4
resolved D-Bus API Documentation
.RS 4
\%http://www.freedesktop.org/wiki/Software/systemd/resolved
.RE