man/sysusers.d.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!--
   5   This file is part of systemd.
   6
   7   Copyright 2014 Lennart Poettering
   8
   9   systemd is free software; you can redistribute it and/or modify it
  10   under the terms of the GNU Lesser General Public License as published by
  11   the Free Software Foundation; either version 2.1 of the License, or
  12   (at your option) any later version.
  13
  14   systemd is distributed in the hope that it will be useful, but
  15   WITHOUT ANY WARRANTY; without even the implied warranty of
  16   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17   Lesser General Public License for more details.
  18
  19   You should have received a copy of the GNU Lesser General Public License
  20   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  21 -->
  22 <refentry id="sysusers.d">
  23
  24         <refentryinfo>
  25                 <title>sysusers.d</title>
  26                 <productname>systemd</productname>
  27
  28                 <authorgroup>
  29                         <author>
  30                                 <contrib>Developer</contrib>
  31                                 <firstname>Lennart</firstname>
  32                                 <surname>Poettering</surname>
  33                                 <email>lennart@poettering.net</email>
  34                         </author>
  35                 </authorgroup>
  36         </refentryinfo>
  37
  38         <refmeta>
  39                 <refentrytitle>sysusers.d</refentrytitle>
  40                 <manvolnum>5</manvolnum>
  41         </refmeta>
  42
  43         <refnamediv>
  44                 <refname>sysusers.d</refname>
  45                 <refpurpose>Declarative allocation of system users and groups</refpurpose>
  46         </refnamediv>
  47
  48         <refsynopsisdiv>
  49                 <para><filename>/usr/lib/sysusers.d/*.conf</filename></para>
  50         </refsynopsisdiv>
  51
  52         <refsect1>
  53                 <title>Description</title>
  54
  55                 <para><command>systemd-sysusers</command> uses the
  56                 files from <filename>sysusers.d</filename> directory
  57                 to create system users and groups at package
  58                 installation or boot time. This tool may be used to
  59                 allocate system users and groups only, it is not
  60                 useful for creating non-system users and groups, as it
  61                 accesses <filename>/etc/passwd</filename> and
  62                 <filename>/etc/group</filename> directly, bypassing
  63                 any more complex user databases, for example any
  64                 database involving NIS or LDAP.</para>
  65         </refsect1>
  66
  67         <refsect1>
  68                 <title>Configuration Format</title>
  69
  70                 <para>Each configuration file shall be named in the
  71                 style of
  72                 <filename><replaceable>package</replaceable>.conf</filename>
  73                 or
  74                 <filename><replaceable>package</replaceable>-<replaceable>part</replaceable>.conf</filename>.
  75                 The second variant should be used when it is desirable
  76                 to make it easy to override just this part of
  77                 configuration.</para>
  78
  79                 <para>The file format is one line per user or group
  80                 containing name, ID, GECOS field description and home directory:</para>
  81
  82                 <programlisting># Type Name ID GECOS
  83 u httpd 440 "HTTP User"
  84 u authd /usr/bin/authd "Authorization user"
  85 g input - -
  86 m authd input
  87 u root 0 "Superuser" /root</programlisting>
  88
  89                 <refsect2>
  90                         <title>Type</title>
  91
  92                         <para>The type consists of a single
  93                         letter. The following line types are
  94                         understood:</para>
  95
  96                         <variablelist>
  97                                 <varlistentry>
  98                                         <term><varname>u</varname></term>
  99                                         <listitem><para>Create a
 100                                         system user and group of the
 101                                         specified name should they not
 102                                         exist yet. The user's primary
 103                                         group will be set to the group
 104                                         bearing the same name. The
 105                                         user's shell will be set to
 106                                         <filename>/sbin/nologin</filename>,
 107                                         the home directory to the
 108                                         specified home directory, or
 109                                         <filename>/</filename> if none
 110                                         is given. The account will be
 111                                         created disabled, so that
 112                                         logins are not
 113                                         allowed.</para></listitem>
 114                                 </varlistentry>
 115
 116                                 <varlistentry>
 117                                         <term><varname>g</varname></term>
 118                                         <listitem><para>Create a
 119                                         system group of the specified
 120                                         name should it not exist
 121                                         yet. Note that
 122                                         <varname>u</varname>
 123                                         implicitly create a matching
 124                                         group. The group will be
 125                                         created with no password
 126                                         set.</para></listitem>
 127                                 </varlistentry>
 128
 129                                 <varlistentry>
 130                                         <term><varname>m</varname></term>
 131                                         <listitem><para>Add a user to
 132                                         a group. If the user or group
 133                                         are not existing yet, they
 134                                         will be implicitly
 135                                         created.</para></listitem>
 136                                 </varlistentry>
 137                         </variablelist>
 138                 </refsect2>
 139
 140                 <refsect2>
 141                         <title>Name</title>
 142
 143                         <para>The name field specifies the user or
 144                         group name. It should be shorter than 31
 145                         characters and avoid any non-ASCII characters,
 146                         and not begin with a numeric character. It is
 147                         strongly recommended to pick user and group
 148                         names that are unlikely to clash with normal
 149                         users created by the administrator. A good
 150                         scheme to guarantee this is by prefixing all
 151                         system and group names with the underscore,
 152                         and avoiding too generic names.</para>
 153
 154                         <para>For <varname>m</varname> lines this
 155                         field should contain the user name to add to a
 156                         group.</para>
 157                 </refsect2>
 158
 159                 <refsect2>
 160                         <title>ID</title>
 161
 162                         <para>For <varname>u</varname> and
 163                         <varname>g</varname> the numeric 32bit UID or
 164                         GID of the user/group. Do not use IDs 65535 or
 165                         4294967295, as they have special placeholder
 166                         meanings. Specify <literal>-</literal> for
 167                         automatic UID/GID allocation for the user or
 168                         group. Alternatively, specify an absolute path
 169                         in the file system. In this case the UID/GID
 170                         is read from the path's owner/group. This is
 171                         useful to create users whose UID/GID match the
 172                         owners of pre-existing files (such as SUID or
 173                         SGID binaries).</para>
 174
 175                         <para>For <varname>m</varname> lines this
 176                         field should contain the group name to add to
 177                         a user to.</para>
 178                 </refsect2>
 179
 180                 <refsect2>
 181                         <title>GECOS</title>
 182
 183                         <para>A short, descriptive string for users to
 184                         be created, enclosed in quotation marks. Note
 185                         that this field may not contain colons.</para>
 186
 187                         <para>Only applies to lines of type
 188                         <varname>u</varname> and should otherwise be
 189                         left unset, or be set to
 190                         <literal>-</literal>.</para>
 191                 </refsect2>
 192
 193                 <refsect2>
 194                         <title>Home Directory</title>
 195
 196                         <para>The home directory for a new system
 197                         user. If omitted defaults to the root
 198                         directory. It is recommended to not
 199                         unnecessarily specify home directories for
 200                         system users, unless software strictly
 201                         requires one to be set.</para>
 202
 203                         <para>Only applies to lines of type
 204                         <varname>u</varname> and should otherwise be
 205                         left unset, or be set to
 206                         <literal>-</literal>.</para>
 207                 </refsect2>
 208
 209         </refsect1>
 210
 211         <refsect1>
 212                 <title>Overriding vendor configuration</title>
 213
 214                 <para>Note that <command>systemd-sysusers</command>
 215                 will do nothing if the specified users or groups
 216                 already exist, so normally there no reason to override
 217                 <filename>sysusers.d</filename> vendor configuration,
 218                 except to block certain users or groups from being
 219                 created.</para>
 220
 221                 <para>Files in <filename>/etc/sysusers.d</filename>
 222                 override files with the same name in
 223                 <filename>/usr/lib/sysusers.d</filename> and
 224                 <filename>/run/sysusers.d</filename>. Files in
 225                 <filename>/run/sysusers.d</filename> override files
 226                 with the same name in
 227                 <filename>/usr/lib/sysusers.d</filename>. The scheme is the same as for
 228                 <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 229                 except for the directory name.</para>
 230
 231                 <para>If the administrator wants to disable a
 232                 configuration file supplied by the vendor, the
 233                 recommended way is to place a symlink to
 234                 <filename>/dev/null</filename> in
 235                 <filename>/etc/sysusers.d/</filename> bearing the
 236                 same filename.</para>
 237         </refsect1>
 238
 239         <refsect1>
 240                 <title>See Also</title>
 241                 <para>
 242                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 243                         <citerefentry><refentrytitle>systemd-sysusers</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 244                         <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 245                 </para>
 246         </refsect1>
 247
 248 </refentry>