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409093fe | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
eea10b26 | 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> |
db9ecf05 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
409093fe | 5 | |
e7e11bbf | 6 | <refentry id="nss-systemd" conditional='ENABLE_NSS_SYSTEMD'> |
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7 | |
8 | <refentryinfo> | |
9 | <title>nss-systemd</title> | |
10 | <productname>systemd</productname> | |
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11 | </refentryinfo> |
12 | ||
13 | <refmeta> | |
14 | <refentrytitle>nss-systemd</refentrytitle> | |
15 | <manvolnum>8</manvolnum> | |
16 | </refmeta> | |
17 | ||
18 | <refnamediv> | |
19 | <refname>nss-systemd</refname> | |
20 | <refname>libnss_systemd.so.2</refname> | |
e9dd6984 | 21 | <refpurpose>UNIX user and group name resolution for user/group lookup via Varlink</refpurpose> |
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22 | </refnamediv> |
23 | ||
24 | <refsynopsisdiv> | |
25 | <para><filename>libnss_systemd.so.2</filename></para> | |
26 | </refsynopsisdiv> | |
27 | ||
28 | <refsect1> | |
29 | <title>Description</title> | |
30 | ||
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31 | <para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS) |
32 | functionality of the GNU C Library (<command>glibc</command>), providing UNIX user and group name | |
33 | resolution for services implementing the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record | |
34 | Lookup API via Varlink</ulink>, such as the system and service manager | |
35 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> (for its | |
36 | <varname>DynamicUser=</varname> feature, see | |
37 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for | |
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38 | details), |
39 | <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
409093fe | 40 | |
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41 | <para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs |
42 | 0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or | |
43 | <filename>/etc/group</filename>, or if these files are missing.</para> | |
44 | ||
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45 | <para>This module preferably utilizes |
46 | <citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
47 | for resolving users and groups, but also works without the service running.</para> | |
48 | ||
409093fe | 49 | <para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with |
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50 | <literal>passwd:</literal>, <literal>group:</literal>, <literal>shadow:</literal> and |
51 | <literal>gshadow:</literal> in <filename>/etc/nsswitch.conf</filename>.</para> | |
409093fe | 52 | |
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53 | <para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> entry of |
54 | the <filename>/etc/nsswitch.conf</filename> lines so that <filename>/etc/passwd</filename>, | |
55 | <filename>/etc/group</filename>, <filename>/etc/shadow</filename> and <filename>/etc/gshadow</filename> | |
56 | based mappings take precedence.</para> | |
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57 | </refsect1> |
58 | ||
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59 | <refsect1> |
60 | <title>Static Drop-In JSON User/Group Records</title> | |
61 | ||
62 | <para>Besides user/group records acquired via the aforementioned Varlink IPC interfaces and the | |
63 | synthesized root and nobody accounts, this module also makes user and group accounts available to the | |
64 | system that are defined in static drop-in files in the <filename>/etc/userdb/</filename>, | |
65 | <filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename> and | |
66 | <filename>/usr/lib/userdb/</filename> directories.</para> | |
67 | ||
68 | <para>This is a simple mechanism to provide static user and group records via JSON drop-in files. Such | |
69 | user records should be defined in the format described by the <ulink | |
d6029680 | 70 | url="https://systemd.io/USER_RECORD">JSON User Records</ulink> specification and be placed in one of the |
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71 | aforementioned directories under a file name composed of the user name suffixed with |
72 | <filename>.user</filename>, with a world-readable access mode. A symlink named after the user record's | |
73 | UID formatted in decimal and suffixed with <filename>.user</filename> pointing to the primary record file | |
74 | should be created as well, in order to allow both lookups by username and by UID. Privileged user record | |
75 | data (e.g. hashed UNIX passwords) may optionally be provided as well, in a pair of separate companion | |
76 | files with the <filename>.user-privileged</filename> suffix. The data should be stored in a regular file | |
77 | named after the user name, suffixed with <filename>.user-privileged</filename>, and a symlink pointing to | |
78 | it, named after the used numeric UID formatted in decimal with the same suffix. These companion files | |
79 | should not be readable to anyone but root. Example:</para> | |
80 | ||
81 | <programlisting>-rw-r--r--. 1 root root 723 May 10 foobar.user | |
82 | -rw-------. 1 root root 123 May 10 foobar.user-privileged | |
83 | lrwxrwxrwx. 1 root root 19 May 10 4711.user -> foobar.user | |
84 | lrwxrwxrwx. 1 root root 19 May 10 4711.user-privileged -> foobar.user-privileged</programlisting> | |
85 | ||
86 | <para>Similarly, group records following the format described in <ulink | |
87 | url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> may be defined, using the file suffixes | |
88 | <filename>.group</filename> and <filename>.group-privileged</filename>.</para> | |
89 | ||
90 | <para>The primary user/group record files (i.e. those with the <filename>.user</filename> and | |
91 | <filename>.group</filename> suffixes) should not contain the <literal>privileged</literal> section as | |
92 | described in the specifications. The privileged user/group record files (i.e. those with the | |
93 | <filename>.user-privileged</filename> and <filename>.group-privileged</filename> suffixes) should | |
94 | contain this section, exclusively.</para> | |
95 | ||
96 | <para>Note that static user/group records generally do not override conflicting records in | |
97 | <filename>/etc/passwd</filename> or <filename>/etc/group</filename> or other account databases. In fact, | |
98 | before dropping in these files a reasonable level of care should be taken to avoid user/group name and | |
99 | UID/GID conflicts.</para> | |
100 | </refsect1> | |
101 | ||
409093fe | 102 | <refsect1> |
4c2cf157 | 103 | <title>Configuration in <filename>/etc/nsswitch.conf</filename></title> |
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104 | |
105 | <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables | |
106 | <command>nss-systemd</command> correctly:</para> | |
107 | ||
94f760ec | 108 | <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf --> |
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109 | <programlisting>passwd: files <command>systemd</command> |
110 | group: files <command>[SUCCESS=merge] systemd</command> | |
111 | shadow: files <command>systemd</command> | |
f43a19ec | 112 | gshadow: files <command>systemd</command> |
409093fe | 113 | |
d296c20f | 114 | hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns |
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115 | networks: files |
116 | ||
117 | protocols: db files | |
118 | services: db files | |
119 | ethers: db files | |
120 | rpc: db files | |
121 | ||
122 | netgroup: nis</programlisting> | |
123 | ||
124 | </refsect1> | |
125 | ||
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126 | <refsect1> |
127 | <title>Example: Mappings provided by <filename>systemd-machined.service</filename></title> | |
128 | ||
129 | <para>The container <literal>rawhide</literal> is spawned using | |
130 | <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>: | |
131 | </para> | |
132 | ||
133 | <programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick | |
134 | Spawning container rawhide on /var/lib/machines/rawhide. | |
135 | Selected user namespace base 20119552 and range 65536. | |
136 | ... | |
137 | ||
138 | $ machinectl --max-addresses=3 | |
139 | MACHINE CLASS SERVICE OS VERSION ADDRESSES | |
140 | rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9 | |
141 | ||
142 | $ getent passwd vu-rawhide-0 vu-rawhide-81 | |
143 | vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin | |
144 | vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin | |
145 | ||
146 | $ getent group vg-rawhide-0 vg-rawhide-81 | |
147 | vg-rawhide-0:*:20119552: | |
148 | vg-rawhide-81:*:20119633: | |
149 | ||
150 | $ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide' | |
151 | vu-rawhide-0 692 ? /usr/lib/systemd/systemd | |
152 | vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald | |
153 | vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd | |
154 | vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved | |
155 | vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind | |
156 | vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only | |
157 | vu-rawhide-0 746 ? /usr/sbin/sshd -D ... | |
158 | vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user | |
159 | vu-rawhide-0 753 ? (sd-pam) | |
160 | vu-rawhide-0 1628 ? login -- zbyszek | |
161 | vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user | |
162 | vu-rawhide-1000 1631 ? (sd-pam) | |
163 | vu-rawhide-1000 1637 pts/8 -zsh | |
164 | </programlisting> | |
165 | </refsect1> | |
166 | ||
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167 | <refsect1> |
168 | <title>See Also</title> | |
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169 | <para><simplelist type="inline"> |
170 | <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
171 | <member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
172 | <member><citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
173 | <member><citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
174 | <member><citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
175 | <member><citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
176 | <member><citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
177 | <member><citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member> | |
178 | <member><citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member> | |
179 | <member><citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry></member> | |
180 | </simplelist></para> | |
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181 | </refsect1> |
182 | ||
183 | </refentry> |