systemd/man/sysusers.d.xml

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<refentry id="sysusers.d">

        <refentryinfo>
                <title>sysusers.d</title>
                <productname>systemd</productname>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </refentryinfo>

        <refmeta>
                <refentrytitle>sysusers.d</refentrytitle>
                <manvolnum>5</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sysusers.d</refname>
                <refpurpose>Declarative allocation of system users and groups</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <para><filename>/usr/lib/sysusers.d/*.conf</filename></para>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><command>systemd-sysusers</command> uses the
                files from <filename>sysusers.d</filename> directory
                to create system users and groups at package
                installation or boot time. This tool may be used to
                allocate system users and groups only, it is not
                useful for creating non-system users and groups, as it
                accesses <filename>/etc/passwd</filename> and
                <filename>/etc/group</filename> directly, bypassing
                any more complex user databases, for example any
                database involving NIS or LDAP.</para>
        </refsect1>

        <refsect1>
                <title>Configuration Format</title>

                <para>Each configuration file shall be named in the
                style of
                <filename><replaceable>package</replaceable>.conf</filename>
                or
                <filename><replaceable>package</replaceable>-<replaceable>part</replaceable>.conf</filename>.
                The second variant should be used when it is desirable
                to make it easy to override just this part of
                configuration.</para>

                <para>The file format is one line per user or group
                containing name, ID, GECOS field description and home directory:</para>

                <programlisting># Type Name ID GECOS
u httpd 440 "HTTP User"
u authd /usr/bin/authd "Authorization user"
g input - -
m authd input
u root 0 "Superuser" /root</programlisting>

                <refsect2>
                        <title>Type</title>

                        <para>The type consists of a single
                        letter. The following line types are
                        understood:</para>

                        <variablelist>
                                <varlistentry>
                                        <term><varname>u</varname></term>
                                        <listitem><para>Create a
                                        system user and group of the
                                        specified name should they not
                                        exist yet. The user's primary
                                        group will be set to the group
                                        bearing the same name. The
                                        user's shell will be set to
                                        <filename>/sbin/nologin</filename>,
                                        the home directory to the
                                        specified home directory, or
                                        <filename>/</filename> if none
                                        is given. The account will be
                                        created disabled, so that
                                        logins are not
                                        allowed.</para></listitem>
                                </varlistentry>

                                <varlistentry>
                                        <term><varname>g</varname></term>
                                        <listitem><para>Create a
                                        system group of the specified
                                        name should it not exist
                                        yet. Note that
                                        <varname>u</varname>
                                        implicitly create a matching
                                        group. The group will be
                                        created with no password
                                        set.</para></listitem>
                                </varlistentry>

                                <varlistentry>
                                        <term><varname>m</varname></term>
                                        <listitem><para>Add a user to
                                        a group. If the user or group
                                        are not existing yet, they
                                        will be implicitly
                                        created.</para></listitem>
                                </varlistentry>

                                <varlistentry>
                                        <term><varname>r</varname></term>
                                        <listitem><para>Add a range of
                                        numeric UIDs/GIDs to the pool
                                        to allocate new UIDs and GIDs
                                        from. If no line of this type
                                        is specified the range of
                                        UIDs/GIDs is set to some
                                        compiled-in default. Note that
                                        both UIDs and GIDs are
                                        allocated from the same pool,
                                        in order to ensure that users
                                        and groups of the same name
                                        are likely to carry the same
                                        numeric UID and
                                        GID.</para></listitem>
                                </varlistentry>

                        </variablelist>
                </refsect2>

                <refsect2>
                        <title>Name</title>

                        <para>The name field specifies the user or
                        group name. It should be shorter than 31
                        characters and avoid any non-ASCII characters,
                        and not begin with a numeric character. It is
                        strongly recommended to pick user and group
                        names that are unlikely to clash with normal
                        users created by the administrator. A good
                        scheme to guarantee this is by prefixing all
                        system and group names with the underscore,
                        and avoiding too generic names.</para>

                        <para>For <varname>m</varname> lines this
                        field should contain the user name to add to a
                        group.</para>

                        <para>For lines of type <varname>r</varname>
                        this field should be set to
                        <literal>-</literal>.</para>
                </refsect2>

                <refsect2>
                        <title>ID</title>

                        <para>For <varname>u</varname> and
                        <varname>g</varname> the numeric 32bit UID or
                        GID of the user/group. Do not use IDs 65535 or
                        4294967295, as they have special placeholder
                        meanings. Specify <literal>-</literal> for
                        automatic UID/GID allocation for the user or
                        group. Alternatively, specify an absolute path
                        in the file system. In this case the UID/GID
                        is read from the path's owner/group. This is
                        useful to create users whose UID/GID match the
                        owners of pre-existing files (such as SUID or
                        SGID binaries).</para>

                        <para>For <varname>m</varname> lines this
                        field should contain the group name to add to
                        a user to.</para>

                        <para>For lines of type <varname>r</varname>
                        this field should be set to a UID/GID range in
                        the format <literal>FROM-TO</literal> where
                        both values are formatted as decimal ASCII
                        numbers. Alternatively, a single UID/GID may
                        be specified formatted as decimal ASCII
                        numbers.</para>
                </refsect2>

                <refsect2>
                        <title>GECOS</title>

                        <para>A short, descriptive string for users to
                        be created, enclosed in quotation marks. Note
                        that this field may not contain colons.</para>

                        <para>Only applies to lines of type
                        <varname>u</varname> and should otherwise be
                        left unset, or be set to
                        <literal>-</literal>.</para>
                </refsect2>

                <refsect2>
                        <title>Home Directory</title>

                        <para>The home directory for a new system
                        user. If omitted defaults to the root
                        directory. It is recommended to not
                        unnecessarily specify home directories for
                        system users, unless software strictly
                        requires one to be set.</para>

                        <para>Only applies to lines of type
                        <varname>u</varname> and should otherwise be
                        left unset, or be set to
                        <literal>-</literal>.</para>
                </refsect2>

        </refsect1>

        <refsect1>
                <title>Overriding vendor configuration</title>

                <para>Note that <command>systemd-sysusers</command>
                will do nothing if the specified users or groups
                already exist, so normally there no reason to override
                <filename>sysusers.d</filename> vendor configuration,
                except to block certain users or groups from being
                created.</para>

                <para>Files in <filename>/etc/sysusers.d</filename>
                override files with the same name in
                <filename>/usr/lib/sysusers.d</filename> and
                <filename>/run/sysusers.d</filename>. Files in
                <filename>/run/sysusers.d</filename> override files
                with the same name in
                <filename>/usr/lib/sysusers.d</filename>. The scheme is the same as for
                <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                except for the directory name.</para>

                <para>If the administrator wants to disable a
                configuration file supplied by the vendor, the
                recommended way is to place a symlink to
                <filename>/dev/null</filename> in
                <filename>/etc/sysusers.d/</filename> bearing the
                same filename.</para>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd-sysusers</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>