man/pam_systemd.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="pam_systemd" conditional='HAVE_PAM' xmlns:xi="http://www.w3.org/2001/XInclude">
   7
   8   <refentryinfo>
   9     <title>pam_systemd</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>pam_systemd</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>pam_systemd</refname>
  20     <refpurpose>Register user sessions in the systemd login manager</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <para><filename>pam_systemd.so</filename></para>
  25   </refsynopsisdiv>
  26
  27   <refsect1>
  28     <title>Description</title>
  29
  30     <para><command>pam_systemd</command> registers user sessions with
  31     the systemd login manager
  32     <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  33     and hence the systemd control group hierarchy.</para>
  34
  35     <para>The module also applies various resource management and runtime parameters to the new session, as
  36     configured in the <ulink url="https://systemd.io/USER_RECORD">JSON User Records</ulink> of the user, when
  37     one is defined.</para>
  38
  39     <para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
  40     following:</para>
  41
  42     <orderedlist>
  43       <listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
  44       either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
  45       changed to the user that is logging in.</para></listitem>
  46
  47       <listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
  48       available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
  49       variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
  50       independent session counter is used.</para></listitem>
  51
  52       <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
  53       the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
  54       scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
  55       systemd user manager instance, is started.</para></listitem>
  56
  57       <listitem><para>The <literal>$TZ</literal>, <literal>$EMAIL</literal> and <literal>$LANG</literal>
  58       environment variables are configured for the user, based on the respective data from the user's JSON
  59       record (if it is defined). Moreover, any environment variables explicitly configured in the user record
  60       are imported, and the umask, nice level, and resource limits initialized.</para></listitem>
  61     </orderedlist>
  62
  63     <para>On logout, this module ensures the following:</para>
  64
  65     <orderedlist>
  66       <listitem><para>If enabled in
  67       <citerefentry><refentrytitle>logind.conf</refentrytitle>
  68       <manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
  69       terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
  70       and so will the user's slice unit.</para></listitem>
  71
  72       <listitem><para>If the last concurrent session of a user ends,
  73       the user runtime directory <filename>/run/user/$UID</filename> and all its
  74       contents are removed, too.</para></listitem>
  75     </orderedlist>
  76
  77     <para>If the system was not booted up with systemd as init system,
  78     this module does nothing and immediately returns
  79     <constant>PAM_SUCCESS</constant>.</para>
  80
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Options</title>
  85
  86     <para>The following options are understood:</para>
  87
  88     <variablelist class='pam-directives'>
  89
  90       <varlistentry>
  91         <term><varname>class=</varname></term>
  92
  93         <listitem><para>Takes a string argument which sets the session class. The
  94         <varname>XDG_SESSION_CLASS</varname> environment variable (see below) takes precedence. See
  95         <citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  96         for a way to query the class of a session. The following session classes are defined:</para>
  97
  98         <table>
  99           <title>Session Classes</title>
 100           <tgroup cols='2' align='left' colsep='1' rowsep='1'>
 101             <colspec colname="name" />
 102             <colspec colname="explanation" />
 103             <thead>
 104               <row>
 105                 <entry>Name</entry>
 106                 <entry>Explanation</entry>
 107               </row>
 108             </thead>
 109             <tbody>
 110               <row>
 111                 <entry><constant>user</constant></entry>
 112                 <entry>A regular interactive user session. This is the default class for sessions for which a TTY or X display is known at session registration time.</entry>
 113               </row>
 114               <row>
 115                 <entry><constant>user-early</constant></entry>
 116                 <entry>Similar to <literal>user</literal> but sessions of this class are not ordered after <filename>systemd-user-sessions.service</filename>, i.e. may be started before regular sessions are allowed to be established. This session class is the default for sessions of the root user that would otherwise qualify for the <constant>user</constant> class, see above. (Added in v256.)</entry>
 117               </row>
 118               <row>
 119                 <entry><constant>greeter</constant></entry>
 120                 <entry>Similar to <literal>user</literal> but for sessions that are spawned by a display manager ephemerally and which prompt the user for login credentials.</entry>
 121               </row>
 122               <row>
 123                 <entry><constant>lock-screen</constant></entry>
 124                 <entry>Similar to <literal>user</literal> but for sessions that are spawned by a display manager ephemerally and which show a lock screen that can be used to unlock locked user accounts or sessions.</entry>
 125               </row>
 126               <row>
 127                 <entry><constant>background</constant></entry>
 128                 <entry>Used for background sessions, such as those invoked by <command>cron</command> and similar tools. This is the default class for sessions for which no TTY or X display is known at session registration time.</entry>
 129               </row>
 130               <row>
 131                 <entry><constant>background-light</constant></entry>
 132                 <entry>Similar to <constant>background</constant>, but sessions of this class will not pull in the <filename>user@.service</filename> of the user, and thus possibly have no services of the user running. (Added in v256.)</entry>
 133               </row>
 134               <row>
 135                 <entry><constant>manager</constant></entry>
 136                 <entry>The <filename>user@.service</filename> service of the user is registered under this session class. (Added in v256.)</entry>
 137               </row>
 138               <row>
 139                 <entry><constant>manager-early</constant></entry>
 140                 <entry>Similar to <constant>manager</constant>, but for the root user. Compare with the <constant>user</constant> vs. <constant>user-early</constant> situation. (Added in v256.)</entry>
 141               </row>
 142             </tbody>
 143           </tgroup>
 144         </table>
 145
 146         <xi:include href="version-info.xml" xpointer="v197"/></listitem>
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><varname>type=</varname></term>
 151
 152         <listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
 153         environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
 154         <literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
 155         <citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 156         details about the session type.</para>
 157
 158         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 159       </varlistentry>
 160
 161       <varlistentry>
 162         <term><varname>desktop=</varname></term>
 163
 164         <listitem><para>Takes a single, short identifier string for the desktop environment. The
 165         <varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
 166         indicate the session desktop used, where this applies and if this information is available. For example:
 167         <literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
 168         capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
 169         url="https://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
 170         Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
 171         like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
 172         <citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 173         further details.</para>
 174
 175         <xi:include href="version-info.xml" xpointer="v240"/></listitem>
 176       </varlistentry>
 177
 178       <varlistentry>
 179         <term><varname>default-capability-bounding-set=</varname></term>
 180         <term><varname>default-capability-ambient-set=</varname></term>
 181
 182         <listitem><para>Takes a comma-separated list of process capabilities
 183         (e.g. <constant>CAP_WAKE_ALARM</constant>, <constant>CAP_BLOCK_SUSPEND</constant>, …) to set for the
 184         invoked session's processes, if the user record does not encode appropriate sets of capabilities
 185         directly. See <citerefentry
 186         project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 187         for details on the capabilities concept. If not specified, the default bounding set is left as is
 188         (i.e. usually contains the full set of capabilities). The default ambient set is set to
 189         <constant>CAP_WAKE_ALARM</constant> for regular users if the PAM session is associated with a local
 190         seat or if it is invoked for the <literal>systemd-user</literal> service. Otherwise defaults to the
 191         empty set.</para>
 192
 193         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 194       </varlistentry>
 195
 196       <varlistentry>
 197         <term><varname>debug</varname><optional>=</optional></term>
 198
 199         <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
 200         debugging information as it operates.</para></listitem>
 201       </varlistentry>
 202     </variablelist>
 203   </refsect1>
 204
 205   <refsect1>
 206     <title>Module Types Provided</title>
 207
 208     <para>Only <option>session</option> is provided.</para>
 209   </refsect1>
 210
 211   <refsect1>
 212     <title>Environment</title>
 213
 214     <para>The following environment variables are initialized by the module and available to the processes of the
 215     user's session:</para>
 216
 217     <variablelist class='environment-variables'>
 218       <varlistentry>
 219         <term><varname>$XDG_SESSION_ID</varname></term>
 220
 221         <listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
 222         considered opaque, although often it is just the audit session ID as reported by
 223         <filename>/proc/self/sessionid</filename>. Each ID will be assigned only once during machine uptime. It may
 224         hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
 225         identifier, as returned by
 226         <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
 227         globally unique identifier.</para></listitem>
 228       </varlistentry>
 229
 230       <varlistentry>
 231         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 232
 233         <listitem><para>Path to a user-private user-writable directory
 234         that is bound to the user login time on the machine. It is
 235         automatically created the first time a user logs in and
 236         removed on the user's final logout. If a user logs in twice at
 237         the same time, both sessions will see the same
 238         <varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
 239         a user logs in once, then logs out again, and logs in again,
 240         the directory contents will have been lost in between, but
 241         applications should not rely on this behavior and must be able
 242         to deal with stale files. To store session-private data in
 243         this directory, the user should include the value of
 244         <varname>$XDG_SESSION_ID</varname> in the filename. This
 245         directory shall be used for runtime file system objects such
 246         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
 247         similar. It is guaranteed that this directory is local and
 248         offers the greatest possible file system feature set the
 249         operating system provides. For further details, see the <ulink
 250         url="https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 251         Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
 252         is not set if the current user is not the original user of the session.</para></listitem>
 253       </varlistentry>
 254
 255       <varlistentry>
 256         <term><varname>$TZ</varname></term>
 257         <term><varname>$EMAIL</varname></term>
 258         <term><varname>$LANG</varname></term>
 259
 260         <listitem><para>If a JSON user record is known for the user logging in these variables are
 261         initialized from the respective data in the record.</para>
 262
 263         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 264       </varlistentry>
 265
 266     </variablelist>
 267
 268     <para>The following environment variables are read by the module and may be used by the PAM service to pass
 269     metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
 270     otherwise they are set by the module, so that these variables are initialized for the session and applications if
 271     known at all.</para>
 272
 273     <variablelist class='environment-variables'>
 274       <varlistentry>
 275         <term><varname>$XDG_SESSION_TYPE</varname></term>
 276
 277         <listitem><para>The session type. This may be used instead of <varname>type=</varname> on the module parameter
 278         line, and is usually preferred.</para>
 279
 280         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 281       </varlistentry>
 282
 283       <varlistentry>
 284         <term><varname>$XDG_SESSION_CLASS</varname></term>
 285
 286         <listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
 287         line, and is usually preferred.</para>
 288
 289         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 290       </varlistentry>
 291
 292       <varlistentry>
 293         <term><varname>$XDG_SESSION_DESKTOP</varname></term>
 294
 295         <listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
 296         parameter line, and is usually preferred.</para>
 297
 298         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 299       </varlistentry>
 300
 301       <varlistentry>
 302         <term><varname>$XDG_SEAT</varname></term>
 303
 304         <listitem><para>The seat name the session shall be registered
 305         for, if any.</para>
 306
 307         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 308       </varlistentry>
 309
 310       <varlistentry>
 311         <term><varname>$XDG_VTNR</varname></term>
 312
 313         <listitem><para>The VT number the session shall be registered
 314         for, if any. (Only applies to seats with a VT available, such
 315         as <literal>seat0</literal>)</para>
 316
 317         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 318       </varlistentry>
 319     </variablelist>
 320
 321     <para>If not set, <command>pam_systemd</command> will initialize
 322     <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
 323     based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
 324   </refsect1>
 325
 326   <refsect1>
 327     <title>Session limits</title>
 328
 329     <para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
 330     can set session scope limits using the PAM context objects. The data for these objects is provided as <constant>NUL</constant>-terminated C strings
 331     and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
 332     they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
 333     which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
 334     by all the user's sessions, is not covered by these limits.
 335     </para>
 336
 337     <para> See
 338     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
 339     Also, see <citerefentry project='man-pages'><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
 340     the context objects.
 341     </para>
 342
 343     <variablelist class='pam-directives'>
 344       <varlistentry>
 345         <term><varname>systemd.memory_max=</varname></term>
 346
 347         <listitem><para>Sets unit <varname>MemoryMax=</varname>.</para>
 348
 349         <xi:include href="version-info.xml" xpointer="v239"/></listitem>
 350       </varlistentry>
 351
 352       <varlistentry>
 353         <term><varname>systemd.tasks_max=</varname></term>
 354
 355         <listitem><para>Sets unit <varname>TasksMax=</varname>.</para>
 356
 357         <xi:include href="version-info.xml" xpointer="v239"/></listitem>
 358       </varlistentry>
 359
 360       <varlistentry>
 361         <term><varname>systemd.cpu_weight=</varname></term>
 362
 363         <listitem><para>Sets unit <varname>CPUWeight=</varname>.</para>
 364
 365         <xi:include href="version-info.xml" xpointer="v239"/></listitem>
 366       </varlistentry>
 367
 368       <varlistentry>
 369         <term><varname>systemd.io_weight=</varname></term>
 370
 371         <listitem><para>Sets unit <varname>IOWeight=</varname>.</para>
 372
 373         <xi:include href="version-info.xml" xpointer="v239"/></listitem>
 374       </varlistentry>
 375
 376       <varlistentry>
 377         <term><varname>systemd.runtime_max_sec=</varname></term>
 378
 379         <listitem><para>Sets unit <varname>RuntimeMaxSec=</varname>.</para>
 380
 381         <xi:include href="version-info.xml" xpointer="v244"/></listitem>
 382       </varlistentry>
 383     </variablelist>
 384
 385     <para>Example data as can be provided from an another PAM module:
 386       <programlisting>
 387 pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
 388 pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
 389 pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
 390 pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
 391 pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);
 392       </programlisting>
 393     </para>
 394
 395   </refsect1>
 396
 397   <refsect1>
 398     <title>Example</title>
 399
 400     <para>Here's an example PAM configuration fragment that allows users sessions to be managed by
 401     <filename>systemd-logind.service</filename>:</para>
 402
 403     <programlisting>#%PAM-1.0
 404 auth      sufficient pam_unix.so
 405 -auth     sufficient pam_systemd_home.so
 406 auth      required   pam_deny.so
 407
 408 account   required   pam_nologin.so
 409 -account  sufficient pam_systemd_home.so
 410 account   sufficient pam_unix.so
 411 account   required   pam_permit.so
 412
 413 -password sufficient pam_systemd_home.so
 414 password  sufficient pam_unix.so sha512 shadow try_first_pass
 415 password  required   pam_deny.so
 416
 417 -session  optional   pam_keyinit.so revoke
 418 -session  optional   pam_loginuid.so
 419 -session  optional   pam_systemd_home.so
 420 <command>-session  optional   pam_systemd.so</command>
 421 session   required   pam_unix.so</programlisting>
 422   </refsect1>
 423
 424   <refsect1>
 425     <title>See Also</title>
 426     <para><simplelist type="inline">
 427       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 428       <member><citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 429       <member><citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 430       <member><citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 431       <member><citerefentry><refentrytitle>pam_systemd_home</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 432       <member><citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 433       <member><citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 434       <member><citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 435       <member><citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 436       <member><citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 437       <member><citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 438       <member><citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 439     </simplelist></para>
 440   </refsect1>
 441
 442 </refentry>