man: document the new nss-systemd behaviour

(This also changes the suggested /etc/nsswitch.conf line to use for
hooking up nss-system to use glibc's [SUCCESS=merge] feature so that we
can properly merge group membership lists).
This commit is contained in:
Lennart Poettering 2019-11-19 16:51:27 +01:00
parent 7d9ad0e5e5
commit 0ba56d3657
1 changed files with 15 additions and 7 deletions

View File

@ -18,7 +18,7 @@
<refnamediv>
<refname>nss-systemd</refname>
<refname>libnss_systemd.so.2</refname>
<refpurpose>Provide UNIX user and group name resolution for dynamic users and groups.</refpurpose>
<refpurpose>Provide UNIX user and group name resolution for user/group lookup via Varlink</refpurpose>
</refnamediv>
<refsynopsisdiv>
@ -28,16 +28,24 @@
<refsect1>
<title>Description</title>
<para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
GNU C Library (<command>glibc</command>), providing UNIX user and group name resolution for dynamic users and
groups allocated through the <varname>DynamicUser=</varname> option in systemd unit files. See
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details on
this option.</para>
<para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS)
functionality of the GNU C Library (<command>glibc</command>), providing UNIX user and group name
resolution for services implementing the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record
Lookup API via Varlink</ulink>, such as the system and service manager
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> (for its
<varname>DynamicUser=</varname> feature, see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
details) or
<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs
0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or
<filename>/etc/group</filename>, or if these files are missing.</para>
<para>This module preferably utilizes
<citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for resolving users and groups, but also works without the service running.</para>
<para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with
<literal>passwd:</literal> and <literal>group:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
@ -54,7 +62,7 @@
<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
<programlisting>passwd: compat mymachines <command>systemd</command>
group: compat mymachines <command>systemd</command>
group: compat [SUCCESS=merge] mymachines [SUCCESS=merge] <command>systemd</command>
shadow: compat
hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname