systemd/man/systemd-sysusers.xml
Zbigniew Jędrzejewski-Szmek ec3917d282 tmpfiles,sysusers: rework path argument handling
Previously, if given an absolute path, we would open the file, but when given a
relative path, we'd attempt to search the directories. If the user wants to open
a file from the search path, allowing paths is very confusing. E.g. with a path
like 'sysusers/foo.conf', we'd try to open '/etc/sysusers.d/sysusers/foo.conf',
'/run/sysusers.d/sysusers/foo.conf', …, and with '../foo.conf', we'd try to open
'/etc/sysusers.d/../foo.conf', '/run/sysusers.d/../foo.conf', …. This just isn't
useful, and in fact for a scheme like sysusers.d and tmpfiles.d where there we
have a flat directory with config files, only searching for plain names can
result in success. When a user specifies a relative path, it's more likely that
they wanted to open some local file. OTOH, to correctly open a local file, e.g.
one that they're just writing, this interface is also awkward, because something
like '$PWD/file.conf' has to be used to open a file with a relative path.

This patch changes the interface so that any path (i.e. an argument with "/") is
used to open a file directly, and only plain basenames are used for searching.

(Note that tpmfiles and sysusers are somewhat special here: their "config files"
make sense without the other config and users are likely to want to test them
without the other config. I was trying to do just that when writing a spec file
for a package and attempting to convert the existing scripts to sysusers and
tmpfiles. The same logic wouldn't apply for example to units or udev rules,
because they generally can only be interpreted with the whole rest of config
also available.)
2024-02-09 17:57:41 +01:00

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<?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="systemd-sysusers"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-sysusers</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-sysusers</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-sysusers</refname>
<refname>systemd-sysusers.service</refname>
<refpurpose>Allocate system users and groups</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>systemd-sysusers</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="opt" rep="repeat"><replaceable>CONFIGFILE</replaceable></arg>
</cmdsynopsis>
<para><filename>systemd-sysusers.service</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-sysusers</command> creates system users and groups, based on files in the format
described in
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
<para>If invoked with no arguments, directives from the configuration files found in the directories
specified by
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>. When
invoked with positional arguments, if option <option>--replace=<replaceable>PATH</replaceable></option>
is specified, arguments specified on the command line are used instead of the configuration file
<replaceable>PATH</replaceable>. Otherwise, just the configuration specified by the command line
arguments is executed. If the string <literal>-</literal> is specified instead of a filename, the
configuration is read from standard input. If the argument is a file name (without any slashes), all
configuration directories are searched for a matching file and the file found that has the highest
priority is executed. If the argument is a path, that file is used directly without searching the
configuration directories for any other matching file.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--root=<replaceable>root</replaceable></option></term>
<listitem><para>Takes a directory path as an argument. All
paths will be prefixed with the given alternate
<replaceable>root</replaceable> path, including config search
paths. </para>
<xi:include href="version-info.xml" xpointer="v215"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--image=<replaceable>image</replaceable></option></term>
<listitem><para>Takes a path to a disk image file or block device node. If specified all operations
are applied to file system in the indicated disk image. This is similar to <option>--root=</option>
but operates on file systems stored in disk images or block devices. The disk image should either
contain just a file system or a set of file systems within a GPT partition table, following the
<ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions
Specification</ulink>. For further information on supported disk images, see
<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
switch of the same name.</para>
<xi:include href="version-info.xml" xpointer="v247"/></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="image-policy-open" />
<varlistentry>
<term><option>--replace=<replaceable>PATH</replaceable></option></term>
<listitem><para>When this option is given, one or more positional arguments
must be specified. All configuration files found in the directories listed in
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
will be read, and the configuration given on the command line will be
handled instead of and with the same priority as the configuration file
<replaceable>PATH</replaceable>.</para>
<para>This option is intended to be used when package installation scripts
are running and files belonging to that package are not yet available on
disk, so their contents must be given on the command line, but the admin
configuration might already exist and should be given higher priority.
</para>
<example>
<title>RPM installation script for radvd</title>
<programlisting>echo 'u radvd - "radvd daemon"' | \
systemd-sysusers --replace=/usr/lib/sysusers.d/radvd.conf -</programlisting>
<para>This will create the radvd user as if
<filename>/usr/lib/sysusers.d/radvd.conf</filename> was already on disk.
An admin might override the configuration specified on the command line by
placing <filename>/etc/sysusers.d/radvd.conf</filename> or even
<filename>/etc/sysusers.d/00-overrides.conf</filename>.</para>
<para>Note that this is the expanded form, and when used in a package, this
would be written using a macro with "radvd" and a file containing the
configuration line as arguments.</para>
</example>
<xi:include href="version-info.xml" xpointer="v238"/>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--dry-run</option></term>
<listitem><para>Process the configuration and figure out what entries would be created, but don't
actually write anything.</para>
<xi:include href="version-info.xml" xpointer="v250"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--inline</option></term>
<listitem><para>Treat each positional argument as a separate configuration
line instead of a file name.</para>
<xi:include href="version-info.xml" xpointer="v238"/></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="cat-config" />
<xi:include href="standard-options.xml" xpointer="tldr" />
<xi:include href="standard-options.xml" xpointer="no-pager" />
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Credentials</title>
<para><command>systemd-sysusers</command> supports the service credentials logic as implemented by
<varname>ImportCredential=</varname>/<varname>LoadCredential=</varname>/<varname>SetCredential=</varname>
(see <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
details). The following credentials are used when passed in:</para>
<variablelist class='system-credentials'>
<varlistentry>
<term><varname>passwd.hashed-password.<replaceable>user</replaceable></varname></term>
<listitem><para>A UNIX hashed password string to use for the specified user, when creating an entry
for it. This is particularly useful for the <literal>root</literal> user as it allows provisioning
the default root password to use via a unit file drop-in or from a container manager passing in this
credential. Note that setting this credential has no effect if the specified user account already
exists. This credential is hence primarily useful in first boot scenarios or systems that are fully
stateless and come up with an empty <filename>/etc/</filename> on every boot.</para>
<xi:include href="version-info.xml" xpointer="v249"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>passwd.plaintext-password.<replaceable>user</replaceable></varname></term>
<listitem><para>Similar to <literal>passwd.hashed-password.<replaceable>user</replaceable></literal>
but expect a literal, plaintext password, which is then automatically hashed before used for the user
account. If both the hashed and the plaintext credential are specified for the same user the
former takes precedence. It's generally recommended to specify the hashed version; however in test
environments with weaker requirements on security it might be easier to pass passwords in plaintext
instead.</para>
<xi:include href="version-info.xml" xpointer="v249"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>passwd.shell.<replaceable>user</replaceable></varname></term>
<listitem><para>Specifies the shell binary to use for the specified account when creating it.</para>
<xi:include href="version-info.xml" xpointer="v249"/></listitem>
</varlistentry>
<varlistentry>
<term><varname>sysusers.extra</varname></term>
<listitem><para>The contents of this credential may contain additional lines to operate on. The
credential contents should follow the same format as any other <filename>sysusers.d/</filename>
drop-in. If this credential is passed it is processed after all of the drop-in files read from the
file system.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
</varlistentry>
</variablelist>
<para>Note that by default the <filename>systemd-sysusers.service</filename> unit file is set up to
inherit the <literal>passwd.hashed-password.root</literal>,
<literal>passwd.plaintext-password.root</literal>, <literal>passwd.shell.root</literal> and
<literal>sysusers.extra</literal> credentials from the service manager. Thus, when invoking a container
with an unpopulated <filename>/etc/</filename> for the first time it is possible to configure the root
user's password to be <literal>systemd</literal> like this:</para>
<para><programlisting># systemd-nspawn --image=… --set-credential=passwd.hashed-password.root:'$y$j9T$yAuRJu1o5HioZAGDYPU5d.$F64ni6J2y2nNQve90M/p0ZP0ECP/qqzipNyaY9fjGpC' …</programlisting></para>
<para>Note again that the data specified in this credential is consulted only when creating an account
for the first time, it may not be used for changing the password or shell of an account that already
exists.</para>
<para>Use <citerefentry project='man-pages'><refentrytitle>mkpasswd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
for generating UNIX password hashes from the command line.</para>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>On success, 0 is returned, a non-zero failure code
otherwise.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
<member><ulink url="https://systemd.io/UIDS-GIDS">Users, Groups, UIDs and GIDs on systemd systems</ulink></member>
<member><citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
<member><citerefentry project='man-pages'><refentrytitle>mkpasswd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>