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https://github.com/systemd/systemd
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![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
Fixes #6639. (This behaviour of systemd-sysusers is long established, so it's better to adjust the documentation rather than change the code. If there are any situations out there where it matters, users must have adjusted to the current behaviour.)
249 lines
9.9 KiB
XML
249 lines
9.9 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2014 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sysusers.d" conditional='ENABLE_SYSUSERS'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sysusers.d</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sysusers.d</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sysusers.d</refname>
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<refpurpose>Declarative allocation of system users and groups</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/etc/sysusers.d/*.conf</filename></para>
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<para><filename>/run/sysusers.d/*.conf</filename></para>
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<para><filename>/usr/lib/sysusers.d/*.conf</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>systemd-sysusers</command> uses the files from <filename>sysusers.d</filename> directory to create
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system users and groups at package installation or boot time. This tool may be used to allocate system users and
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groups only, it is not useful for creating non-system (i.e. regular, "human") users and groups, as it accesses
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<filename>/etc/passwd</filename> and <filename>/etc/group</filename> directly, bypassing any more complex user
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databases, for example any database involving NIS or LDAP.</para>
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</refsect1>
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<refsect1>
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<title>Configuration Directories and Precedence</title>
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<para>Each configuration file shall be named in the style of
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<filename><replaceable>package</replaceable>.conf</filename> or
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<filename><replaceable>package</replaceable>-<replaceable>part</replaceable>.conf</filename>.
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The second variant should be used when it is desirable to make it
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easy to override just this part of configuration.</para>
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<para>Files in <filename>/etc/sysusers.d</filename> override files
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with the same name in <filename>/usr/lib/sysusers.d</filename> and
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<filename>/run/sysusers.d</filename>. Files in
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<filename>/run/sysusers.d</filename> override files with the same
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name in <filename>/usr/lib/sysusers.d</filename>. Packages should
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install their configuration files in
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<filename>/usr/lib/sysusers.d</filename>. Files in
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<filename>/etc/sysusers.d</filename> are reserved for the local
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administrator, who may use this logic to override the
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configuration files installed by vendor packages. All
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configuration files are sorted by their filename in lexicographic
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order, regardless of which of the directories they reside in. If
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multiple files specify the same path, the entry in the file with
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the lexicographically earliest name will be applied. All later
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entries for the same user and group names will be logged as warnings.
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</para>
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<para>If the administrator wants to disable a configuration file
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supplied by the vendor, the recommended way is to place a symlink
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to <filename>/dev/null</filename> in
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<filename>/etc/sysusers.d/</filename> bearing the same filename.
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</para>
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</refsect1>
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<refsect1>
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<title>Configuration File Format</title>
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<para>The file format is one line per user or group containing
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name, ID, GECOS field description and home directory:</para>
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<programlisting># Type Name ID GECOS
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u httpd 440 "HTTP User"
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u authd /usr/bin/authd "Authorization user"
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g input - -
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m authd input
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u root 0 "Superuser" /root</programlisting>
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<para>Empty lines and lines beginning with the <literal>#</literal> character are ignored, and may be used for
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commenting.</para>
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<refsect2>
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<title>Type</title>
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<para>The type consists of a single letter. The following line
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types are understood:</para>
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<variablelist>
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<varlistentry>
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<term><varname>u</varname></term>
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<listitem><para>Create a system user and group of the
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specified name should they not exist yet. The user's primary
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group will be set to the group bearing the same name. The
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user's shell will be set to
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<filename>/sbin/nologin</filename>, the home directory to
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the specified home directory, or <filename>/</filename> if
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none is given. The account will be created disabled, so that
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logins are not allowed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>g</varname></term>
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<listitem><para>Create a system group of the specified name
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should it not exist yet. Note that <varname>u</varname>
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implicitly create a matching group. The group will be
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created with no password set.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>m</varname></term>
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<listitem><para>Add a user to a group. If the user or group
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do not exist yet, they will be implicitly
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created.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>r</varname></term>
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<listitem><para>Add a range of numeric UIDs/GIDs to the pool
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to allocate new UIDs and GIDs from. If no line of this type
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is specified, the range of UIDs/GIDs is set to some
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compiled-in default. Note that both UIDs and GIDs are
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allocated from the same pool, in order to ensure that users
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and groups of the same name are likely to carry the same
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numeric UID and GID.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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<refsect2>
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<title>Name</title>
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<para>The name field specifies the user or group name. The specified name must consist only of the characters a-z,
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A-Z, 0-9, <literal>_</literal> and <literal>-</literal>, except for the first character which must be one of a-z,
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A-Z or <literal>_</literal> (i.e. numbers and <literal>-</literal> are not permitted as first character). The
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user/group name must have at least one character, and at most 31.</para>
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<para>It is strongly recommended to pick user and group names that are unlikely to clash with normal users
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created by the administrator. A good scheme to guarantee this is by prefixing all system and group names with the
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underscore, and avoiding too generic names.</para>
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<para>For <varname>m</varname> lines, this field should contain
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the user name to add to a group.</para>
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<para>For lines of type <varname>r</varname>, this field should
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be set to <literal>-</literal>.</para>
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</refsect2>
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<refsect2>
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<title>ID</title>
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<para>For <varname>u</varname> and <varname>g</varname>, the
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numeric 32-bit UID or GID of the user/group. Do not use IDs 65535
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or 4294967295, as they have special placeholder meanings.
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Specify <literal>-</literal> for automatic UID/GID allocation
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for the user or group. Alternatively, specify an absolute path
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in the file system. In this case, the UID/GID is read from the
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path's owner/group. This is useful to create users whose UID/GID
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match the owners of pre-existing files (such as SUID or SGID
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binaries).</para>
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<para>For <varname>m</varname> lines, this field should contain
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the group name to add to a user to.</para>
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<para>For lines of type <varname>r</varname>, this field should
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be set to a UID/GID range in the format
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<literal>FROM-TO</literal>, where both values are formatted as
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decimal ASCII numbers. Alternatively, a single UID/GID may be
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specified formatted as decimal ASCII numbers.</para>
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</refsect2>
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<refsect2>
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<title>GECOS</title>
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<para>A short, descriptive string for users to be created,
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enclosed in quotation marks. Note that this field may not
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contain colons.</para>
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<para>Only applies to lines of type <varname>u</varname> and
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should otherwise be left unset, or be set to
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<literal>-</literal>.</para>
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</refsect2>
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<refsect2>
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<title>Home Directory</title>
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<para>The home directory for a new system user. If omitted,
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defaults to the root directory. It is recommended to not
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unnecessarily specify home directories for system users, unless
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software strictly requires one to be set.</para>
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<para>Only applies to lines of type <varname>u</varname> and
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should otherwise be left unset, or be set to
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<literal>-</literal>.</para>
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</refsect2>
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</refsect1>
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<refsect1>
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<title>Idempotence</title>
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<para>Note that <command>systemd-sysusers</command> will do
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nothing if the specified users or groups already exist, so
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normally, there is no reason to override
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<filename>sysusers.d</filename> vendor configuration, except to
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block certain users or groups from being created.</para>
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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-sysusers</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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