man/pam_systemd.xml

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