man/sysusers.d.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   4   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   5 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   6 <refentry id="sysusers.d" conditional='ENABLE_SYSUSERS'
   7     xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>sysusers.d</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>sysusers.d</refentrytitle>
  16     <manvolnum>5</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>sysusers.d</refname>
  21     <refpurpose>Declarative allocation of system users and groups</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><simplelist>
  26       <member><filename>/etc/sysusers.d/*.conf</filename></member>
  27       <member><filename>/run/sysusers.d/*.conf</filename></member>
  28       <member><filename>/usr/lib/sysusers.d/*.conf</filename></member>
  29     </simplelist></para>
  30
  31     <programlisting>
  32 #Type Name       ID                  GECOS              Home directory Shell
  33 u     user_name  uid                 "User Description" /home/dir      /path/to/shell
  34 u     user_name  uid:gid             "User Description" /home/dir      /path/to/shell
  35 u     user_name  /file/owned/by/user "User Description" /home/dir      /path/to/shell
  36 g     group_name gid
  37 g     group_name /file/owned/by/group
  38 m     user_name  group_name
  39 r     -          lowest-highest</programlisting>
  40   </refsynopsisdiv>
  41
  42   <refsect1>
  43     <title>Description</title>
  44
  45     <para><command>systemd-sysusers</command> uses the files from
  46     <filename>sysusers.d</filename> directory to create system users and groups and
  47     to add users to groups, at package installation or boot time. This tool may be
  48     used to allocate system users and groups only, it is not useful for creating
  49     non-system (i.e. regular, "human") users and groups, as it accesses
  50     <filename>/etc/passwd</filename> and <filename>/etc/group</filename> directly,
  51     bypassing any more complex user databases, for example any database involving NIS
  52     or LDAP.</para>
  53   </refsect1>
  54
  55   <refsect1>
  56     <title>Configuration Directories and Precedence</title>
  57
  58     <para>Each configuration file shall be named in the style of
  59     <filename><replaceable>package</replaceable>.conf</filename> or
  60     <filename><replaceable>package</replaceable>-<replaceable>part</replaceable>.conf</filename>.
  61     The second variant should be used when it is desirable to make it
  62     easy to override just this part of configuration.</para>
  63
  64     <para>Files in <filename>/etc/sysusers.d</filename> override files
  65     with the same name in <filename>/usr/lib/sysusers.d</filename> and
  66     <filename>/run/sysusers.d</filename>. Files in
  67     <filename>/run/sysusers.d</filename> override files with the same
  68     name in <filename>/usr/lib/sysusers.d</filename>. Packages should
  69     install their configuration files in
  70     <filename>/usr/lib/sysusers.d</filename>. Files in
  71     <filename>/etc/sysusers.d</filename> are reserved for the local
  72     administrator, who may use this logic to override the
  73     configuration files installed by vendor packages. All
  74     configuration files are sorted by their filename in lexicographic
  75     order, regardless of which of the directories they reside in. If
  76     multiple files specify the same path, the entry in the file with
  77     the lexicographically earliest name will be applied. All later
  78     entries for the same user and group names will be logged as warnings.
  79     </para>
  80
  81     <para>If the administrator wants to disable a configuration file
  82     supplied by the vendor, the recommended way is to place a symlink
  83     to <filename>/dev/null</filename> in
  84     <filename>/etc/sysusers.d/</filename> bearing the same filename.
  85     </para>
  86   </refsect1>
  87
  88   <refsect1>
  89     <title>Configuration File Format</title>
  90
  91     <para>The file format is one line per user or group containing name, ID, GECOS
  92     field description, home directory, and login shell:</para>
  93
  94     <programlisting>#Type Name     ID             GECOS                 Home directory Shell
  95 u     httpd    404            "HTTP User"
  96 u     _authd   /usr/bin/authd "Authorization user"
  97 u     postgres -              "Postgresql Database" /var/lib/pgsql /usr/libexec/postgresdb
  98 g     input    -              -
  99 m     _authd   input
 100 u     root     0              "Superuser"           /root          /bin/zsh
 101 r     -        500-900
 102 </programlisting>
 103
 104     <para>Empty lines and lines beginning with the <literal>#</literal> character are ignored, and may be used for
 105     commenting.</para>
 106
 107     <refsect2>
 108       <title>Type</title>
 109
 110       <para>The type consists of a single letter. The following line
 111       types are understood:</para>
 112
 113       <variablelist>
 114         <varlistentry>
 115           <term><varname>u</varname></term>
 116           <listitem><para>Create a system user and group of the specified name should
 117           they not exist yet. The user's primary group will be set to the group
 118           bearing the same name unless the ID field specifies it. The account will be
 119           created disabled, so that logins are not allowed.</para>
 120
 121           <xi:include href="version-info.xml" xpointer="v215"/></listitem>
 122         </varlistentry>
 123
 124         <varlistentry>
 125           <term><varname>g</varname></term>
 126           <listitem><para>Create a system group of the specified name
 127           should it not exist yet. Note that <varname>u</varname>
 128           implicitly creates a matching group. The group will be
 129           created with no password set.</para>
 130
 131           <xi:include href="version-info.xml" xpointer="v215"/></listitem>
 132         </varlistentry>
 133
 134         <varlistentry>
 135           <term><varname>m</varname></term>
 136           <listitem><para>Add a user to a group. If the user or group
 137           do not exist yet, they will be implicitly
 138           created.</para>
 139
 140           <xi:include href="version-info.xml" xpointer="v215"/></listitem>
 141         </varlistentry>
 142
 143         <varlistentry>
 144           <term><varname>r</varname></term>
 145           <listitem><para>Add a range of numeric UIDs/GIDs to the pool
 146           to allocate new UIDs and GIDs from. If no line of this type
 147           is specified, the range of UIDs/GIDs is set to some
 148           compiled-in default. Note that both UIDs and GIDs are
 149           allocated from the same pool, in order to ensure that users
 150           and groups of the same name are likely to carry the same
 151           numeric UID and GID.</para>
 152
 153           <xi:include href="version-info.xml" xpointer="v216"/></listitem>
 154         </varlistentry>
 155
 156       </variablelist>
 157     </refsect2>
 158
 159     <refsect2>
 160       <title>Name</title>
 161
 162       <para>The name field specifies the user or group name. The specified name must consist only of the characters a-z,
 163       A-Z, 0-9, <literal>_</literal> and <literal>-</literal>, except for the first character which must be one of a-z,
 164       A-Z or <literal>_</literal> (i.e. numbers and <literal>-</literal> are not permitted as first character). The
 165       user/group name must have at least one character, and at most 31.</para>
 166
 167       <para>For further details about the syntax of user/group names, see <ulink
 168       url="https://systemd.io/USER_NAMES">User/Group Name Syntax</ulink>.</para>
 169
 170       <para>It is strongly recommended to pick user and group names that are unlikely to clash with normal users
 171       created by the administrator. A good scheme to guarantee this is by prefixing all system and group names with the
 172       underscore, and avoiding too generic names.</para>
 173
 174       <para>For <varname>m</varname> lines, this field should contain
 175       the user name to add to a group.</para>
 176
 177       <para>For lines of type <varname>r</varname>, this field should
 178       be set to <literal>-</literal>.</para>
 179     </refsect2>
 180
 181     <refsect2>
 182       <title>ID</title>
 183
 184       <para>For <varname>u</varname> and <varname>g</varname>, the
 185       numeric 32-bit UID or GID of the user/group. Do not use IDs 65535
 186       or 4294967295, as they have special placeholder meanings.
 187       Specify <literal>-</literal> for automatic UID/GID allocation
 188       for the user or group (this is strongly recommended unless it is strictly
 189       necessary to use a specific UID or GID). Alternatively, specify an absolute path
 190       in the file system. In this case, the UID/GID is read from the
 191       path's owner/group. This is useful to create users whose UID/GID
 192       match the owners of pre-existing files (such as SUID or SGID
 193       binaries).
 194       The syntaxes <literal><replaceable>uid</replaceable>:<replaceable>gid</replaceable></literal> and
 195       <literal><replaceable>uid</replaceable>:<replaceable>groupname</replaceable></literal> are supported to
 196       allow creating users with specific primary groups. The given group must be created explicitly, or it
 197       must already exist. Specifying <literal>-</literal> for the UID in these syntaxes is also supported.
 198       </para>
 199
 200       <para>For <varname>m</varname> lines, this field should contain
 201       the group name to add to a user to.</para>
 202
 203       <para>For lines of type <varname>r</varname>, this field should
 204       be set to a UID/GID range in the format
 205       <literal>FROM-TO</literal>, where both values are formatted as
 206       decimal ASCII numbers. Alternatively, a single UID/GID may be
 207       specified formatted as decimal ASCII numbers.</para>
 208     </refsect2>
 209
 210     <refsect2>
 211       <title>GECOS</title>
 212
 213       <para>A short, descriptive string for users to be created, enclosed in
 214       quotation marks. Note that this field may not contain colons.</para>
 215
 216       <para>Only applies to lines of type <varname>u</varname> and should otherwise
 217       be left unset (or <literal>-</literal>).</para>
 218     </refsect2>
 219
 220     <refsect2>
 221       <title>Home Directory</title>
 222
 223       <para>The home directory for a new system user. If omitted, defaults to the
 224       root directory.</para>
 225
 226       <para>Only applies to lines of type <varname>u</varname> and should otherwise
 227       be left unset (or <literal>-</literal>). It is recommended to omit this, unless
 228       software strictly requires a home directory to be set.</para>
 229
 230       <para><command>systemd-sysusers</command> only sets the home directory record in the
 231       user database. To actually create the directory, consider adding a corresponding
 232       <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 233       fragment.</para>
 234     </refsect2>
 235
 236     <refsect2>
 237       <title>Shell</title>
 238
 239       <para>The login shell of the user. If not specified, this will be set to
 240       <filename>/usr/sbin/nologin</filename>, except if the UID of the user is 0, in
 241       which case <filename>/bin/sh</filename> will be used.</para>
 242
 243       <para>Only applies to lines of type <varname>u</varname> and should otherwise
 244       be left unset (or <literal>-</literal>). It is recommended to omit this, unless
 245       a shell different <filename>/usr/sbin/nologin</filename> must be used.</para>
 246     </refsect2>
 247   </refsect1>
 248
 249   <refsect1>
 250     <title>Specifiers</title>
 251
 252     <para>Specifiers can be used in the <literal>Name</literal>, <literal>ID</literal>,
 253     <literal>GECOS</literal>, <literal>Home directory</literal>, and <literal>Shell</literal> fields. An
 254     unknown or unresolvable specifier is treated as invalid configuration. The following expansions are
 255     understood:</para>
 256
 257     <table class='specifiers'>
 258       <title>Specifiers available</title>
 259       <tgroup cols='3' align='left' colsep='1' rowsep='1'>
 260         <colspec colname="spec" />
 261         <colspec colname="mean" />
 262         <colspec colname="detail" />
 263         <thead>
 264           <row>
 265             <entry>Specifier</entry>
 266             <entry>Meaning</entry>
 267             <entry>Details</entry>
 268           </row>
 269         </thead>
 270         <tbody>
 271           <xi:include href="standard-specifiers.xml" xpointer="a"/>
 272           <xi:include href="standard-specifiers.xml" xpointer="A"/>
 273           <xi:include href="standard-specifiers.xml" xpointer="b"/>
 274           <xi:include href="standard-specifiers.xml" xpointer="B"/>
 275           <xi:include href="standard-specifiers.xml" xpointer="H"/>
 276           <xi:include href="standard-specifiers.xml" xpointer="l"/>
 277           <xi:include href="standard-specifiers.xml" xpointer="m"/>
 278           <xi:include href="standard-specifiers.xml" xpointer="M"/>
 279           <xi:include href="standard-specifiers.xml" xpointer="o"/>
 280           <xi:include href="standard-specifiers.xml" xpointer="T"/>
 281           <xi:include href="standard-specifiers.xml" xpointer="v"/>
 282           <xi:include href="standard-specifiers.xml" xpointer="V"/>
 283           <xi:include href="standard-specifiers.xml" xpointer="w"/>
 284           <xi:include href="standard-specifiers.xml" xpointer="W"/>
 285           <xi:include href="standard-specifiers.xml" xpointer="percent"/>
 286         </tbody>
 287       </tgroup>
 288     </table>
 289   </refsect1>
 290
 291   <refsect1>
 292     <title>Idempotence</title>
 293
 294     <para>Note that <command>systemd-sysusers</command> will do nothing if the
 295     specified users or groups already exist or the users are members of specified
 296     groups, so normally there is no reason to override
 297     <filename>sysusers.d</filename> vendor configuration, except to block certain
 298     users or groups from being created.</para>
 299   </refsect1>
 300
 301   <refsect1>
 302     <title>See Also</title>
 303     <para><simplelist type="inline">
 304       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 305       <member><citerefentry><refentrytitle>systemd-sysusers</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 306     </simplelist></para>
 307   </refsect1>
 308
 309 </refentry>