1NSS-RESOLVE(8)                    nss-resolve                   NSS-RESOLVE(8)
2
3
4

NAME

6       nss-resolve, libnss_resolve.so.2 - Hostname resolution via
7       systemd-resolved.service
8

SYNOPSIS

10       libnss_resolve.so.2
11

DESCRIPTION

13       nss-resolve is a plug-in module for the GNU Name Service Switch (NSS)
14       functionality of the GNU C Library (glibc) enabling it to resolve
15       hostnames via the systemd-resolved(8) local network name resolution
16       service. It replaces the nss-dns plug-in module that traditionally
17       resolves hostnames via DNS.
18
19       To activate the NSS module, add "resolve [!UNAVAIL=return]" to the line
20       starting with "hosts:" in /etc/nsswitch.conf. Specifically, it is
21       recommended to place "resolve" early in /etc/nsswitch.conf's "hosts:"
22       line. It should be before the "files" entry, since systemd-resolved
23       supports /etc/hosts internally, but with caching. To the contrary, it
24       should be after "mymachines", to give hostnames given to local VMs and
25       containers precedence over names received over DNS. Finally, we
26       recommend placing "dns" somewhere after "resolve", to fall back to
27       nss-dns if systemd-resolved.service is not available.
28
29       Note that systemd-resolved will synthesize DNS resource records in a
30       few cases, for example for "localhost" and the current local hostname,
31       see systemd-resolved(8) for the full list. This duplicates the
32       functionality of nss-myhostname(8), but it is still recommended (see
33       examples below) to keep nss-myhostname configured in
34       /etc/nsswitch.conf, to keep those names resolveable if systemd-resolved
35       is not running.
36
37       Please keep in mind that nss-myhostname (and nss-resolve) also resolve
38       in the other direction — from locally attached IP addresses to
39       hostnames. If you rely on that lookup being provided by DNS, you might
40       want to order things differently.
41
42       Communication between nss-resolve and systemd-resolved.service takes
43       place via the /run/systemd/resolve/io.systemd.Resolve AF_UNIX socket.
44

ENVIRONMENT VARIABLES

46       $SYSTEMD_NSS_RESOLVE_VALIDATE
47           Takes a boolean argument. When false, cryptographic validation of
48           resource records via DNSSEC will be disabled. This may be useful
49           for testing, or when system time is known to be unreliable.
50
51       $SYSTEMD_NSS_RESOLVE_SYNTHESIZE
52           Takes a boolean argument. When false, synthetic records, e.g. for
53           the local host name, will not be returned. See section SYNTHETIC
54           RECORDS in systemd-resolved.service(8) for more information. This
55           may be useful to query the "public" resource records, independent
56           of the configuration of the local machine.
57
58       $SYSTEMD_NSS_RESOLVE_CACHE
59           Takes a boolean argument. When false, the cache of previously
60           queried records will not be used by systemd-resolved(8).
61
62       $SYSTEMD_NSS_RESOLVE_ZONE
63           Takes a boolean argument. When false, answers using locally
64           registered public LLMNR/mDNS resource records will not be returned.
65
66       $SYSTEMD_NSS_RESOLVE_TRUST_ANCHOR
67           Takes a boolean argument. When false, answers using locally
68           configured trust anchors will not be used.
69
70       $SYSTEMD_NSS_RESOLVE_NETWORK
71           Takes a boolean argument. When false, answers will be returned
72           without using the network, i.e. either from local sources or the
73           cache in systemd-resolved(8).
74

EXAMPLE

76       Here is an example /etc/nsswitch.conf file that enables nss-resolve
77       correctly:
78
79           passwd:         compat systemd
80           group:          compat [SUCCESS=merge] systemd
81           shadow:         compat systemd
82           gshadow:        files systemd
83
84           hosts:          mymachines resolve [!UNAVAIL=return] files myhostname dns
85           networks:       files
86
87           protocols:      db files
88           services:       db files
89           ethers:         db files
90           rpc:            db files
91
92           netgroup:       nis
93

SEE ALSO

95       systemd(1), systemd-resolved(8), nss-systemd(8), nss-myhostname(8),
96       nss-mymachines(8), nsswitch.conf(5), systemd.syntax(5)
97
98
99
100systemd 253                                                     NSS-RESOLVE(8)
Impressum