mirror of
https://github.com/systemd/systemd.git
synced 2024-11-23 02:03:37 +08:00
d1b04f47e3
This has been a glaring omission the docs: when people create .user/.group/.user-privileged/.group-privileged drop-in files, they should also create matching .membership files.
195 lines
11 KiB
XML
195 lines
11 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="nss-systemd" conditional='ENABLE_NSS_SYSTEMD'>
|
|
|
|
<refentryinfo>
|
|
<title>nss-systemd</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>nss-systemd</refentrytitle>
|
|
<manvolnum>8</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>nss-systemd</refname>
|
|
<refname>libnss_systemd.so.2</refname>
|
|
<refpurpose>UNIX user and group name resolution for user/group lookup via Varlink</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<para><filename>libnss_systemd.so.2</filename></para>
|
|
</refsynopsisdiv>
|
|
|
|
<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 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),
|
|
<citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or <citerefentry><refentrytitle>systemd-machined.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>, <literal>group:</literal>, <literal>shadow:</literal> and
|
|
<literal>gshadow:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
|
|
|
|
<para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> entry of
|
|
the <filename>/etc/nsswitch.conf</filename> lines so that <filename>/etc/passwd</filename>,
|
|
<filename>/etc/group</filename>, <filename>/etc/shadow</filename> and <filename>/etc/gshadow</filename>
|
|
based mappings take precedence.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Static Drop-In JSON User/Group Records</title>
|
|
|
|
<para>Besides user/group records acquired via the aforementioned Varlink IPC interfaces and the
|
|
synthesized root and nobody accounts, this module also makes user and group accounts available to the
|
|
system that are defined in static drop-in files in the <filename>/etc/userdb/</filename>,
|
|
<filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename> and
|
|
<filename>/usr/lib/userdb/</filename> directories.</para>
|
|
|
|
<para>This is a simple mechanism to provide static user and group records via JSON drop-in files. Such
|
|
user records should be defined in the format described by the <ulink
|
|
url="https://systemd.io/USER_RECORD">JSON User Records</ulink> specification and be placed in one of the
|
|
aforementioned directories under a file name composed of the user name suffixed with
|
|
<filename>.user</filename>, with a world-readable access mode. A symlink named after the user record's
|
|
UID formatted in decimal and suffixed with <filename>.user</filename> pointing to the primary record file
|
|
should be created as well, in order to allow both lookups by username and by UID. Privileged user record
|
|
data (e.g. hashed UNIX passwords) may optionally be provided as well, in a pair of separate companion
|
|
files with the <filename>.user-privileged</filename> suffix. The data should be stored in a regular file
|
|
named after the user name, suffixed with <filename>.user-privileged</filename>, and a symlink pointing to
|
|
it, named after the used numeric UID formatted in decimal with the same suffix. These companion files
|
|
should not be readable to anyone but root. Example:</para>
|
|
|
|
<programlisting>-rw-r--r--. 1 root root 723 May 10 foobar.user
|
|
-rw-------. 1 root root 123 May 10 foobar.user-privileged
|
|
lrwxrwxrwx. 1 root root 19 May 10 4711.user -> foobar.user
|
|
lrwxrwxrwx. 1 root root 19 May 10 4711.user-privileged -> foobar.user-privileged</programlisting>
|
|
|
|
<para>Similarly, group records following the format described in <ulink
|
|
url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> may be defined, using the file suffixes
|
|
<filename>.group</filename> and <filename>.group-privileged</filename>.</para>
|
|
|
|
<para>The primary user/group record files (i.e. those with the <filename>.user</filename> and
|
|
<filename>.group</filename> suffixes) should not contain the <literal>privileged</literal> section as
|
|
described in the specifications. The privileged user/group record files (i.e. those with the
|
|
<filename>.user-privileged</filename> and <filename>.group-privileged</filename> suffixes) should
|
|
contain this section, exclusively.</para>
|
|
|
|
<para>In addition to the two types of user record files and the two types of group record files there's a
|
|
fifth type of file that may be placed in the searched directories: files that indicate membership of
|
|
users in groups. Specifically, for every pair of user/group where the user shall be a member of a group a
|
|
file named
|
|
<literal><replaceable>username</replaceable>:<replaceable>groupname</replaceable>.membership</literal>
|
|
should be created, i.e. the textual UNIX user name, followed by a colon, followed by the textual UNIX
|
|
group name, suffixed by <literal>.membership</literal>. The contents of these files are currently not
|
|
read, and the files should be created empty. The mere existence of these files is enough to effect a
|
|
user/group membership. If a program provides user and/or group record files in the searched directories,
|
|
it should always also create such files, both for primary and auxiliary group memberships.</para>
|
|
|
|
<para>Note that static user/group records generally do not override conflicting records in
|
|
<filename>/etc/passwd</filename> or <filename>/etc/group</filename> or other account databases. In fact,
|
|
before dropping in these files a reasonable level of care should be taken to avoid user/group name and
|
|
UID/GID conflicts.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Configuration in <filename>/etc/nsswitch.conf</filename></title>
|
|
|
|
<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
|
|
<command>nss-systemd</command> correctly:</para>
|
|
|
|
<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
|
|
<programlisting>passwd: files <command>systemd</command>
|
|
group: files <command>[SUCCESS=merge] systemd</command>
|
|
shadow: files <command>systemd</command>
|
|
gshadow: files <command>systemd</command>
|
|
|
|
hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns
|
|
networks: files
|
|
|
|
protocols: db files
|
|
services: db files
|
|
ethers: db files
|
|
rpc: db files
|
|
|
|
netgroup: nis</programlisting>
|
|
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Example: Mappings provided by <filename>systemd-machined.service</filename></title>
|
|
|
|
<para>The container <literal>rawhide</literal> is spawned using
|
|
<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
|
|
</para>
|
|
|
|
<programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
|
|
Spawning container rawhide on /var/lib/machines/rawhide.
|
|
Selected user namespace base 20119552 and range 65536.
|
|
...
|
|
|
|
$ machinectl --max-addresses=3
|
|
MACHINE CLASS SERVICE OS VERSION ADDRESSES
|
|
rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
|
|
|
|
$ getent passwd vu-rawhide-0 vu-rawhide-81
|
|
vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin
|
|
vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin
|
|
|
|
$ getent group vg-rawhide-0 vg-rawhide-81
|
|
vg-rawhide-0:*:20119552:
|
|
vg-rawhide-81:*:20119633:
|
|
|
|
$ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide'
|
|
vu-rawhide-0 692 ? /usr/lib/systemd/systemd
|
|
vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald
|
|
vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd
|
|
vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved
|
|
vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind
|
|
vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
|
|
vu-rawhide-0 746 ? /usr/sbin/sshd -D ...
|
|
vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user
|
|
vu-rawhide-0 753 ? (sd-pam)
|
|
vu-rawhide-0 1628 ? login -- zbyszek
|
|
vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user
|
|
vu-rawhide-1000 1631 ? (sd-pam)
|
|
vu-rawhide-1000 1637 pts/8 -zsh
|
|
</programlisting>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
<para><simplelist type="inline">
|
|
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
|
|
<member><citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
|
|
<member><citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
|
|
</simplelist></para>
|
|
</refsect1>
|
|
|
|
</refentry>
|