1SYSTEMD.DNSSD(5)                 systemd.dnssd                SYSTEMD.DNSSD(5)
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NAME

6       systemd.dnssd - DNS-SD configuration
7

SYNOPSIS

9       network_service.dnssd
10

DESCRIPTION

12       DNS-SD setup is performed by systemd-resolved(8).
13
14       The main network service file must have the extension .dnssd; other
15       extensions are ignored.
16
17       The .dnssd files are read from the files located in the system network
18       directories /usr/lib/systemd/dnssd and /usr/local/lib/systemd/dnssd,
19       the volatile runtime network directory /run/systemd/dnssd and the local
20       administration network directory /etc/systemd/dnssd. All configuration
21       files are collectively sorted and processed in lexical order,
22       regardless of the directories in which they live. However, files with
23       identical filenames replace each other. Files in /etc/ have the highest
24       priority, files in /run/ take precedence over files with the same name
25       in /usr/lib/. This can be used to override a system-supplied
26       configuration file with a local file if needed.
27
28       Along with the network service file foo.dnssd, a "drop-in" directory
29       foo.dnssd.d/ may exist. All files with the suffix ".conf" from this
30       directory will be parsed after the file itself is parsed. This is
31       useful to alter or add configuration settings, without having to modify
32       the main configuration file. Each drop-in file must have appropriate
33       section headers.
34
35       In addition to /etc/systemd/dnssd, drop-in ".d" directories can be
36       placed in /usr/lib/systemd/dnssd or /run/systemd/dnssd directories.
37       Drop-in files in /etc/ take precedence over those in /run/ which in
38       turn take precedence over those in /usr/lib/ or /usr/local/lib. Drop-in
39       files under any of these directories take precedence over the main
40       network service file wherever located.
41

[SERVICE] SECTION OPTIONS

43       The network service file contains a [Service] section, which specifies
44       a discoverable network service announced in a local network with
45       Multicast DNS broadcasts.
46
47       Name=
48           An instance name of the network service as defined in the section
49           4.1.1 of RFC 6763[1], e.g.  "webserver".
50
51           The option supports simple specifier expansion. The following
52           expansions are understood:
53
54           Table 1. Specifiers available
55           ┌──────────┬─────────────────────┬────────────────────────┐
56Specifier Meaning             Details                
57           ├──────────┼─────────────────────┼────────────────────────┤
58           │"%a"      │ Architecture        │ A short string         │
59           │          │                     │ identifying the        │
60           │          │                     │ architecture of the    │
61           │          │                     │ local system. A        │
62           │          │                     │ string such as x86,    │
63           │          │                     │ x86-64 or arm64.       │
64           │          │                     │ See the                │
65           │          │                     │ architectures          │
66           │          │                     │ defined for            │
67           │          │                     │ ConditionArchitecture=
68           │          │                     │ in systemd.unit(5)
69           │          │                     │ for a full list.       │
70           ├──────────┼─────────────────────┼────────────────────────┤
71           │"%A"      │ Operating system    │ The operating system   │
72           │          │ image version       │ image version          │
73           │          │                     │ identifier of the      │
74           │          │                     │ running system, as     │
75           │          │                     │ read from the          │
76           │          │                     │ IMAGE_VERSION= field   │
77           │          │                     │ of /etc/os-release. If │
78           │          │                     │ not set, resolves to   │
79           │          │                     │ an empty string. See   │
80           │          │                     │ os-release(5) for more │
81           │          │                     │ information.           │
82           ├──────────┼─────────────────────┼────────────────────────┤
83           │"%b"      │ Boot ID             │ The boot ID of the     │
84           │          │                     │ running system,        │
85           │          │                     │ formatted as string.   │
86           │          │                     │ See random(4) for more │
87           │          │                     │ information.           │
88           ├──────────┼─────────────────────┼────────────────────────┤
89           │"%B"      │ Operating system    │ The operating system   │
90           │          │ build ID            │ build identifier of    │
91           │          │                     │ the running system, as │
92           │          │                     │ read from the          │
93           │          │                     │ BUILD_ID= field of     │
94           │          │                     │ /etc/os-release. If    │
95           │          │                     │ not set, resolves to   │
96           │          │                     │ an empty string. See   │
97           │          │                     │ os-release(5) for more │
98           │          │                     │ information.           │
99           ├──────────┼─────────────────────┼────────────────────────┤
100           │"%H"      │ Host name           │ The hostname of the    │
101           │          │                     │ running system.        │
102           ├──────────┼─────────────────────┼────────────────────────┤
103           │"%m"      │ Machine ID          │ The machine ID of the  │
104           │          │                     │ running system,        │
105           │          │                     │ formatted as string.   │
106           │          │                     │ See machine-id(5) for  │
107           │          │                     │ more information.      │
108           ├──────────┼─────────────────────┼────────────────────────┤
109           │"%M"      │ Operating system    │ The operating system   │
110           │          │ image identifier    │ image identifier of    │
111           │          │                     │ the running system, as │
112           │          │                     │ read from the          │
113           │          │                     │ IMAGE_ID= field of     │
114           │          │                     │ /etc/os-release. If    │
115           │          │                     │ not set, resolves to   │
116           │          │                     │ an empty string. See   │
117           │          │                     │ os-release(5) for more │
118           │          │                     │ information.           │
119           ├──────────┼─────────────────────┼────────────────────────┤
120           │"%o"      │ Operating system ID │ The operating system   │
121           │          │                     │ identifier of the      │
122           │          │                     │ running system, as     │
123           │          │                     │ read from the ID=
124           │          │                     │ field of               │
125           │          │                     │ /etc/os-release. See   │
126           │          │                     │ os-release(5) for more │
127           │          │                     │ information.           │
128           ├──────────┼─────────────────────┼────────────────────────┤
129           │"%v"      │ Kernel release      │ Identical to uname -r  
130           │          │                     │ output.                │
131           ├──────────┼─────────────────────┼────────────────────────┤
132           │"%w"      │ Operating system    │ The operating system   │
133           │          │ version ID          │ version identifier of  │
134           │          │                     │ the running system, as │
135           │          │                     │ read from the          │
136           │          │                     │ VERSION_ID= field of   │
137           │          │                     │ /etc/os-release. If    │
138           │          │                     │ not set, resolves to   │
139           │          │                     │ an empty string. See   │
140           │          │                     │ os-release(5) for more │
141           │          │                     │ information.           │
142           ├──────────┼─────────────────────┼────────────────────────┤
143           │"%W"      │ Operating system    │ The operating system   │
144           │          │ variant ID          │ variant identifier of  │
145           │          │                     │ the running system, as │
146           │          │                     │ read from the          │
147           │          │                     │ VARIANT_ID= field of   │
148           │          │                     │ /etc/os-release. If    │
149           │          │                     │ not set, resolves to   │
150           │          │                     │ an empty string. See   │
151           │          │                     │ os-release(5) for more │
152           │          │                     │ information.           │
153           ├──────────┼─────────────────────┼────────────────────────┤
154           │"%%"      │ Single percent sign │ Use "%%" in place of   │
155           │          │                     │ "%" to specify a       │
156           │          │                     │ single percent sign.   │
157           └──────────┴─────────────────────┴────────────────────────┘
158
159       Type=
160           A type of the network service as defined in the section 4.1.2 of
161           RFC 6763[1], e.g.  "_http._tcp".
162
163       Port=
164           An IP port number of the network service.
165
166       Priority=
167           A priority number set in SRV resource records corresponding to the
168           network service.
169
170       Weight=
171           A weight number set in SRV resource records corresponding to the
172           network service.
173
174       TxtText=
175           A whitespace-separated list of arbitrary key/value pairs conveying
176           additional information about the named service in the corresponding
177           TXT resource record, e.g.  "path=/portal/index.html". Keys and
178           values can contain C-style escape sequences which get translated
179           upon reading configuration files.
180
181           This option together with TxtData= may be specified more than once,
182           in which case multiple TXT resource records will be created for the
183           service. If the empty string is assigned to this option, the list
184           is reset and all prior assignments will have no effect.
185
186       TxtData=
187           A whitespace-separated list of arbitrary key/value pairs conveying
188           additional information about the named service in the corresponding
189           TXT resource record where values are base64-encoded string
190           representing any binary data, e.g.
191           "data=YW55IGJpbmFyeSBkYXRhCg==". Keys can contain C-style escape
192           sequences which get translated upon reading configuration files.
193
194           This option together with TxtText= may be specified more than once,
195           in which case multiple TXT resource records will be created for the
196           service. If the empty string is assigned to this option, the list
197           is reset and all prior assignments will have no effect.
198

EXAMPLES

200       Example 1. HTTP service
201
202           # /etc/systemd/dnssd/http.dnssd
203           [Service]
204           Name=%H
205           Type=_http._tcp
206           Port=80
207           TxtText=path=/stats/index.html t=temperature_sensor
208
209       This makes the http server running on the host discoverable in the
210       local network given MulticastDNS is enabled on the network interface.
211
212       Now the utility "resolvectl" should be able to resolve the service to
213       the host's name:
214
215           $ resolvectl service meteo._http._tcp.local
216           meteo._http._tcp.local: meteo.local:80 [priority=0, weight=0]
217                                   169.254.208.106%senp0s21f0u2u4
218                                   fe80::213:3bff:fe49:8aa%senp0s21f0u2u4
219                                   path=/stats/index.html
220                                   t=temperature_sensor
221                                   (meteo/_http._tcp/local)
222
223           -- Information acquired via protocol mDNS/IPv6 in 4.0ms.
224           -- Data is authenticated: yes
225
226       "Avahi" running on a different host in the same local network should
227       see the service as well:
228
229           $ avahi-browse -a -r
230           + enp3s0 IPv6 meteo                                         Web Site             local
231           + enp3s0 IPv4 meteo                                         Web Site             local
232           = enp3s0 IPv6 meteo                                         Web Site             local
233              hostname = [meteo.local]
234              address = [fe80::213:3bff:fe49:8aa]
235              port = [80]
236              txt = ["path=/stats/index.html" "t=temperature_sensor"]
237           = enp3s0 IPv4 meteo                                         Web Site             local
238              hostname = [meteo.local]
239              address = [169.254.208.106]
240              port = [80]
241              txt = ["path=/stats/index.html" "t=temperature_sensor"]
242

SEE ALSO

244       systemd(1), systemd-resolved.service(8), resolvectl(1)
245

NOTES

247        1. RFC 6763
248           https://tools.ietf.org/html/rfc6763
249
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252systemd 253                                                   SYSTEMD.DNSSD(5)
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