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9a515f0a55
This specifes two new optional fields for /etc/os-release: IMAGE_VERSION= and IMAGE_ID= that are supposed to identify the image of the current booted system by name and version. This is inspired by the versioning stuff in https://github.com/systemd/mkosi/pull/683. In environments where pre-built images are installed and updated as a whole the existing os-release version/distro identifier are not sufficient to describe the system's version, as they describe only the distro an image is built from, but not the image itself, even if that image is deployed many times on many systems, and even if that image contains more resources than just the RPMs/DEBs. In particular, "mkosi" is a tool for building disk images based on distro RPMs with additional resources dropped in. The combination of all of these together with their versions should also carry an identifier and version, and that's what IMAGE_VERSION= and IMAGE_ID= is supposed to be.
300 lines
13 KiB
XML
300 lines
13 KiB
XML
<?xml version="1.0"?>
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<!--*-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-or-later -->
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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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</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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<programlisting>
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#Type Name ID GECOS Home directory Shell
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u user_name uid "User Description" /home/dir /path/to/shell
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u user_name uid:gid "User Description" /home/dir /path/to/shell
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u user_name /file/owned/by/user "User Description" /home/dir /path/to/shell
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g group_name gid
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g group_name /file/owned/by/group
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m user_name group_name
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r - lowest-highest</programlisting>
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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
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<filename>sysusers.d</filename> directory to create system users and groups and
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to add users to groups, at package installation or boot time. This tool may be
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used to allocate system users and groups only, it is not useful for creating
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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,
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bypassing any more complex user databases, for example any database involving NIS
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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 name, ID, GECOS
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field description, home directory, and login shell:</para>
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<programlisting>#Type Name ID GECOS Home directory Shell
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u httpd 404 "HTTP User"
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u _authd /usr/bin/authd "Authorization user"
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u postgres - "Postgresql Database" /var/lib/pgsql /usr/libexec/postgresdb
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g input - -
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m _authd input
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u root 0 "Superuser" /root /bin/zsh
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r - 500-900
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</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 specified name should
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they not exist yet. The user's primary group will be set to the group
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bearing the same name unless the ID field specifies it. The account will be
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created disabled, so that 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 creates 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>For further details about the syntax of user/group names, see <ulink
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url="https://systemd.io/USER_NAMES">User/Group Name Syntax</ulink>.</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 (this is strongly recommended unless it is strictly
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necessary to use a specific UID or GID). 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).
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The syntaxes <literal><replaceable>uid</replaceable>:<replaceable>gid</replaceable></literal> and
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<literal><replaceable>uid</replaceable>:<replaceable>groupname</replaceable></literal> are supported to
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allow creating users with specific primary groups. The given group must be created explicitly, or it
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must already exist. Specifying <literal>-</literal> for the UID in these syntaxes is also supported.
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</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, enclosed in
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quotation marks. Note that this field may not contain colons.</para>
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<para>Only applies to lines of type <varname>u</varname> and should otherwise
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be left unset (or <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, defaults to the
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root directory.</para>
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<para>Only applies to lines of type <varname>u</varname> and should otherwise
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be left unset (or <literal>-</literal>). It is recommended to omit this, unless
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software strictly requires a home directory to be set.</para>
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<para><command>systemd-sysusers</command> only sets the home directory record in the
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user database. To actually create the directory, consider adding a corresponding
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<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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fragment.</para>
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</refsect2>
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<refsect2>
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<title>Shell</title>
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<para>The login shell of the user. If not specified, this will be set to
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<filename>/usr/sbin/nologin</filename>, except if the UID of the user is 0, in
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which case <filename>/bin/sh</filename> will be used.</para>
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<para>Only applies to lines of type <varname>u</varname> and should otherwise
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be left unset (or <literal>-</literal>). It is recommended to omit this, unless
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a shell different <filename>/usr/sbin/nologin</filename> must be used.</para>
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</refsect2>
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</refsect1>
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<refsect1>
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<title>Specifiers</title>
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<para>Specifiers can be used in the <literal>Name</literal>, <literal>ID</literal>,
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<literal>GECOS</literal>, <literal>Home directory</literal>, and <literal>Shell</literal> fields. An
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unknown or unresolvable specifier is treated as invalid configuration. The following expansions are
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understood:</para>
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<table class='specifiers'>
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<title>Specifiers available</title>
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<tgroup cols='3' align='left' colsep='1' rowsep='1'>
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<colspec colname="spec" />
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<colspec colname="mean" />
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<colspec colname="detail" />
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<thead>
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<row>
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<entry>Specifier</entry>
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<entry>Meaning</entry>
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<entry>Details</entry>
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</row>
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</thead>
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<tbody>
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<xi:include href="standard-specifiers.xml" xpointer="a"/>
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<xi:include href="standard-specifiers.xml" xpointer="A"/>
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<xi:include href="standard-specifiers.xml" xpointer="b"/>
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<xi:include href="standard-specifiers.xml" xpointer="B"/>
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<xi:include href="standard-specifiers.xml" xpointer="H"/>
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<xi:include href="standard-specifiers.xml" xpointer="l"/>
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<xi:include href="standard-specifiers.xml" xpointer="m"/>
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<xi:include href="standard-specifiers.xml" xpointer="M"/>
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<xi:include href="standard-specifiers.xml" xpointer="o"/>
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<xi:include href="standard-specifiers.xml" xpointer="T"/>
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<xi:include href="standard-specifiers.xml" xpointer="v"/>
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<xi:include href="standard-specifiers.xml" xpointer="V"/>
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<xi:include href="standard-specifiers.xml" xpointer="w"/>
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<xi:include href="standard-specifiers.xml" xpointer="W"/>
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<xi:include href="standard-specifiers.xml" xpointer="percent"/>
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</tbody>
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</tgroup>
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</table>
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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 nothing if the
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specified users or groups already exist or the users are members of specified
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groups, so normally there is no reason to override
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<filename>sysusers.d</filename> vendor configuration, except to block certain
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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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