man/pam_systemd.xml

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   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="pam_systemd" conditional='HAVE_PAM'>
  14
  15   <refentryinfo>
  16     <title>pam_systemd</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>pam_systemd</refentrytitle>
  31     <manvolnum>8</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>pam_systemd</refname>
  36     <refpurpose>Register user sessions in the systemd login manager</refpurpose>
  37   </refnamediv>
  38
  39   <refsynopsisdiv>
  40     <para><filename>pam_systemd.so</filename></para>
  41   </refsynopsisdiv>
  42
  43   <refsect1>
  44     <title>Description</title>
  45
  46     <para><command>pam_systemd</command> registers user sessions with
  47     the systemd login manager
  48     <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  49     and hence the systemd control group hierarchy.</para>
  50
  51     <para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
  52     following:</para>
  53
  54     <orderedlist>
  55       <listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
  56       either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
  57       changed to the user that is logging in.</para></listitem>
  58
  59       <listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
  60       available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
  61       variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
  62       independent session counter is used.</para></listitem>
  63
  64       <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
  65       the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
  66       scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
  67       systemd user manager instance, is started.  </para></listitem>
  68     </orderedlist>
  69
  70     <para>On logout, this module ensures the following:</para>
  71
  72     <orderedlist>
  73       <listitem><para>If enabled in
  74       <citerefentry><refentrytitle>logind.conf</refentrytitle>
  75       <manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
  76       terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
  77       and so will the user's slice unit.</para></listitem>
  78
  79       <listitem><para>If the last concurrent session of a user ends,
  80       the user runtime directory <filename>/run/user/$UID</filename> and all its
  81       contents are removed, too.</para></listitem>
  82     </orderedlist>
  83
  84     <para>If the system was not booted up with systemd as init system,
  85     this module does nothing and immediately returns
  86     <constant>PAM_SUCCESS</constant>.</para>
  87
  88   </refsect1>
  89
  90   <refsect1>
  91     <title>Options</title>
  92
  93     <para>The following options are understood:</para>
  94
  95     <variablelist class='pam-directives'>
  96
  97       <varlistentry>
  98         <term><option>class=</option></term>
  99
 100         <listitem><para>Takes a string argument which sets the session
 101         class. The XDG_SESSION_CLASS environmental variable takes
 102         precedence. One of
 103         <literal>user</literal>,
 104         <literal>greeter</literal>,
 105         <literal>lock-screen</literal> or
 106         <literal>background</literal>. See
 107         <citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 108         for details about the session class.</para></listitem>
 109       </varlistentry>
 110
 111       <varlistentry>
 112         <term><option>type=</option></term>
 113
 114         <listitem><para>Takes a string argument which sets the session
 115         type. The XDG_SESSION_TYPE environmental variable takes
 116         precedence. One of
 117         <literal>unspecified</literal>,
 118         <literal>tty</literal>,
 119         <literal>x11</literal>,
 120         <literal>wayland</literal> or
 121         <literal>mir</literal>. See
 122         <citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 123         for details about the session type.</para></listitem>
 124       </varlistentry>
 125
 126       <varlistentry>
 127         <term><option>debug<optional>=</optional></option></term>
 128
 129         <listitem><para>Takes an optional
 130         boolean argument. If yes or without
 131         the argument, the module will log
 132         debugging information as it
 133         operates.</para></listitem>
 134       </varlistentry>
 135     </variablelist>
 136   </refsect1>
 137
 138   <refsect1>
 139     <title>Module Types Provided</title>
 140
 141     <para>Only <option>session</option> is provided.</para>
 142   </refsect1>
 143
 144   <refsect1>
 145     <title>Environment</title>
 146
 147     <para>The following environment variables are set for the
 148     processes of the user's session:</para>
 149
 150     <variablelist class='environment-variables'>
 151       <varlistentry>
 152         <term><varname>$XDG_SESSION_ID</varname></term>
 153
 154         <listitem><para>A session identifier, suitable to be used in
 155         filenames. The string itself should be considered opaque,
 156         although often it is just the audit session ID as reported by
 157         <filename>/proc/self/sessionid</filename>. Each ID will be
 158         assigned only once during machine uptime. It may hence be used
 159         to uniquely label files or other resources of this
 160         session.</para></listitem>
 161       </varlistentry>
 162
 163       <varlistentry>
 164         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 165
 166         <listitem><para>Path to a user-private user-writable directory
 167         that is bound to the user login time on the machine. It is
 168         automatically created the first time a user logs in and
 169         removed on the user's final logout. If a user logs in twice at
 170         the same time, both sessions will see the same
 171         <varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
 172         a user logs in once, then logs out again, and logs in again,
 173         the directory contents will have been lost in between, but
 174         applications should not rely on this behavior and must be able
 175         to deal with stale files. To store session-private data in
 176         this directory, the user should include the value of
 177         <varname>$XDG_SESSION_ID</varname> in the filename. This
 178         directory shall be used for runtime file system objects such
 179         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
 180         similar. It is guaranteed that this directory is local and
 181         offers the greatest possible file system feature set the
 182         operating system provides. For further details, see the <ulink
 183         url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 184         Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
 185         is not set if the current user is not the original user of the session.</para></listitem>
 186       </varlistentry>
 187
 188     </variablelist>
 189
 190     <para>The following environment variables are read by the module
 191     and may be used by the PAM service to pass metadata to the
 192     module:</para>
 193
 194     <variablelist class='environment-variables'>
 195       <varlistentry>
 196         <term><varname>$XDG_SESSION_TYPE</varname></term>
 197
 198         <listitem><para>The session type. This may be used instead of
 199         <option>session=</option> on the module parameter line, and is
 200         usually preferred.</para></listitem>
 201       </varlistentry>
 202
 203       <varlistentry>
 204         <term><varname>$XDG_SESSION_CLASS</varname></term>
 205
 206         <listitem><para>The session class. This may be used instead of
 207         <option>class=</option> on the module parameter line, and is
 208         usually preferred.</para></listitem>
 209       </varlistentry>
 210
 211       <varlistentry>
 212         <term><varname>$XDG_SESSION_DESKTOP</varname></term>
 213
 214         <listitem><para>A single, short identifier string for the
 215         desktop environment. This may be used to indicate the session
 216         desktop used, where this applies and if this information is
 217         available. For example: <literal>GNOME</literal>, or
 218         <literal>KDE</literal>. It is recommended to use the same
 219         identifiers and capitalization as for
 220         <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the
 221         <ulink
 222         url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop
 223         Entry Specification</ulink>. (However, note that
 224         <varname>$XDG_SESSION_DESKTOP</varname> only takes a single
 225         item, and not a colon-separated list like
 226         <varname>$XDG_CURRENT_DESKTOP</varname>.) See
 227         <citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 228         for more details.</para></listitem>
 229       </varlistentry>
 230
 231       <varlistentry>
 232         <term><varname>$XDG_SEAT</varname></term>
 233
 234         <listitem><para>The seat name the session shall be registered
 235         for, if any.</para></listitem>
 236       </varlistentry>
 237
 238       <varlistentry>
 239         <term><varname>$XDG_VTNR</varname></term>
 240
 241         <listitem><para>The VT number the session shall be registered
 242         for, if any. (Only applies to seats with a VT available, such
 243         as <literal>seat0</literal>)</para></listitem>
 244       </varlistentry>
 245     </variablelist>
 246
 247     <para>If not set, <command>pam_systemd</command> will determine the
 248     values for <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
 249     based on the <varname>$DISPLAY</varname> variable.</para>
 250   </refsect1>
 251
 252   <refsect1>
 253     <title>Session limits</title>
 254
 255     <para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
 256     can set session scope limits using the PAM context objects. The data for these objects is provided as NUL-terminated C strings
 257     and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
 258     they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
 259     which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
 260     by all the user's sessions, is not covered by these limits.
 261     </para>
 262
 263     <para> See
 264     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
 265     Also, see <citerefentry><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
 266     the context objects.
 267     </para>
 268
 269     <variablelist>
 270       <varlistentry>
 271         <term><varname>systemd.memory_max</varname></term>
 272
 273         <listitem><para>Sets unit <varname>MemoryMax=</varname>.</para></listitem>
 274       </varlistentry>
 275
 276       <varlistentry>
 277         <term><varname>systemd.tasks_max</varname></term>
 278
 279         <listitem><para>Sets unit <varname>TasksMax=</varname>.</para></listitem>
 280       </varlistentry>
 281
 282       <varlistentry>
 283         <term><varname>systemd.cpu_weight</varname></term>
 284
 285         <listitem><para>Sets unit <varname>CPUWeight=</varname>.</para></listitem>
 286       </varlistentry>
 287
 288       <varlistentry>
 289         <term><varname>systemd.io_weight</varname></term>
 290
 291         <listitem><para>Sets unit <varname>IOWeight=</varname>.</para></listitem>
 292       </varlistentry>
 293     </variablelist>
 294
 295     <para>Example data as can be provided from an another PAM module:
 296       <programlisting>
 297 pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
 298 pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
 299 pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
 300 pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
 301       </programlisting>
 302     </para>
 303
 304   </refsect1>
 305
 306   <refsect1>
 307     <title>Example</title>
 308
 309     <programlisting>#%PAM-1.0
 310 auth       required     pam_unix.so
 311 auth       required     pam_nologin.so
 312 account    required     pam_unix.so
 313 password   required     pam_unix.so
 314 session    required     pam_unix.so
 315 session    required     pam_loginuid.so
 316 session    required     pam_systemd.so</programlisting>
 317   </refsect1>
 318
 319   <refsect1>
 320     <title>See Also</title>
 321     <para>
 322       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 323       <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 324       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 325       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 326       <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 327       <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 328       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 329       <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 330       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 331       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 332       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 333     </para>
 334   </refsect1>
 335
 336 </refentry>