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d296c20f1f
I am pretty sure /etc/hosts (i.e. an explicitly configured, local, trusted database) should be useful for overriding the automatic myhostname logic. resolved's internal logic handles it that way and hence we should suggest it in the NSS fallback line, too. Let's also bring the factory file back into sync with what the docs say. And update the prose a bit too, to actually match what we recommend.
138 lines
6.4 KiB
XML
138 lines
6.4 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="nss-systemd" conditional='ENABLE_NSS_SYSTEMD'>
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<refentryinfo>
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<title>nss-systemd</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>nss-systemd</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>nss-systemd</refname>
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<refname>libnss_systemd.so.2</refname>
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<refpurpose>UNIX user and group name resolution for user/group lookup via Varlink</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>libnss_systemd.so.2</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS)
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functionality of the GNU C Library (<command>glibc</command>), providing UNIX user and group name
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resolution for services implementing the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record
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Lookup API via Varlink</ulink>, such as the system and service manager
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> (for its
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<varname>DynamicUser=</varname> feature, see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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details),
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<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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<para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs
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0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or
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<filename>/etc/group</filename>, or if these files are missing.</para>
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<para>This module preferably utilizes
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<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for resolving users and groups, but also works without the service running.</para>
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<para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with
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<literal>passwd:</literal> and <literal>group:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
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<para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> or
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<literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines so that
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<filename>/etc/passwd</filename> and <filename>/etc/group</filename> based mappings take precedence.</para>
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</refsect1>
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<refsect1>
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<title>Configuration in <filename>/etc/nsswitch.conf</filename></title>
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<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
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<command>nss-systemd</command> correctly:</para>
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<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
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<programlisting>passwd: compat <command>systemd</command>
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group: compat [SUCCESS=merge] <command>systemd</command>
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shadow: compat
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hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis</programlisting>
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</refsect1>
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<refsect1>
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<title>Example: Mappings provided by <filename>systemd-machined.service</filename></title>
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<para>The container <literal>rawhide</literal> is spawned using
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<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
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</para>
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<programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
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Spawning container rawhide on /var/lib/machines/rawhide.
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Selected user namespace base 20119552 and range 65536.
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...
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$ machinectl --max-addresses=3
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MACHINE CLASS SERVICE OS VERSION ADDRESSES
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rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
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$ getent passwd vu-rawhide-0 vu-rawhide-81
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vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin
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vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin
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$ getent group vg-rawhide-0 vg-rawhide-81
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vg-rawhide-0:*:20119552:
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vg-rawhide-81:*:20119633:
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$ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide'
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vu-rawhide-0 692 ? /usr/lib/systemd/systemd
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vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald
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vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd
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vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved
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vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind
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vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
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vu-rawhide-0 746 ? /usr/sbin/sshd -D ...
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vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user
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vu-rawhide-0 753 ? (sd-pam)
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vu-rawhide-0 1628 ? login -- zbyszek
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vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user
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vu-rawhide-1000 1631 ? (sd-pam)
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vu-rawhide-1000 1637 pts/8 -zsh
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</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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