man/pam_systemd.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="pam_systemd" conditional='HAVE_PAM'>
   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>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
  36     following:</para>
  37
  38     <orderedlist>
  39       <listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
  40       either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
  41       changed to the user that is logging in.</para></listitem>
  42
  43       <listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
  44       available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
  45       variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
  46       independent session counter is used.</para></listitem>
  47
  48       <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
  49       the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
  50       scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
  51       systemd user manager instance, is started.  </para></listitem>
  52     </orderedlist>
  53
  54     <para>On logout, this module ensures the following:</para>
  55
  56     <orderedlist>
  57       <listitem><para>If enabled in
  58       <citerefentry><refentrytitle>logind.conf</refentrytitle>
  59       <manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
  60       terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
  61       and so will the user's slice unit.</para></listitem>
  62
  63       <listitem><para>If the last concurrent session of a user ends,
  64       the user runtime directory <filename>/run/user/$UID</filename> and all its
  65       contents are removed, too.</para></listitem>
  66     </orderedlist>
  67
  68     <para>If the system was not booted up with systemd as init system,
  69     this module does nothing and immediately returns
  70     <constant>PAM_SUCCESS</constant>.</para>
  71
  72   </refsect1>
  73
  74   <refsect1>
  75     <title>Options</title>
  76
  77     <para>The following options are understood:</para>
  78
  79     <variablelist class='pam-directives'>
  80
  81       <varlistentry>
  82         <term><varname>class=</varname></term>
  83
  84         <listitem><para>Takes a string argument which sets the session class. The <varname>XDG_SESSION_CLASS</varname>
  85         environment variable (see below) takes precedence. One of <literal>user</literal>, <literal>greeter</literal>,
  86         <literal>lock-screen</literal> or <literal>background</literal>. See
  87         <citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  88         details about the session class.</para></listitem>
  89       </varlistentry>
  90
  91       <varlistentry>
  92         <term><varname>type=</varname></term>
  93
  94         <listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
  95         environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
  96         <literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
  97         <citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  98         details about the session type.</para></listitem>
  99       </varlistentry>
 100
 101       <varlistentry>
 102         <term><varname>desktop=</varname></term>
 103
 104         <listitem><para>Takes a single, short identifier string for the desktop environment. The
 105         <varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
 106         indicate the session desktop used, where this applies and if this information is available. For example:
 107         <literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
 108         capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
 109         url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
 110         Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
 111         like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
 112         <citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 113         further details.</para></listitem>
 114       </varlistentry>
 115
 116       <varlistentry>
 117         <term><varname>debug</varname><optional>=</optional></term>
 118
 119         <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
 120         debugging information as it operates.</para></listitem>
 121       </varlistentry>
 122     </variablelist>
 123   </refsect1>
 124
 125   <refsect1>
 126     <title>Module Types Provided</title>
 127
 128     <para>Only <option>session</option> is provided.</para>
 129   </refsect1>
 130
 131   <refsect1>
 132     <title>Environment</title>
 133
 134     <para>The following environment variables are initialized by the module and available to the processes of the
 135     user's session:</para>
 136
 137     <variablelist class='environment-variables'>
 138       <varlistentry>
 139         <term><varname>$XDG_SESSION_ID</varname></term>
 140
 141         <listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
 142         considered opaque, although often it is just the audit session ID as reported by
 143         <filename>/proc/self/sessionid</filename>. Each ID will be assigned only once during machine uptime. It may
 144         hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
 145         identifier, as returned by
 146         <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
 147         globally unique identifier for the current session.</para></listitem>
 148       </varlistentry>
 149
 150       <varlistentry>
 151         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 152
 153         <listitem><para>Path to a user-private user-writable directory
 154         that is bound to the user login time on the machine. It is
 155         automatically created the first time a user logs in and
 156         removed on the user's final logout. If a user logs in twice at
 157         the same time, both sessions will see the same
 158         <varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
 159         a user logs in once, then logs out again, and logs in again,
 160         the directory contents will have been lost in between, but
 161         applications should not rely on this behavior and must be able
 162         to deal with stale files. To store session-private data in
 163         this directory, the user should include the value of
 164         <varname>$XDG_SESSION_ID</varname> in the filename. This
 165         directory shall be used for runtime file system objects such
 166         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
 167         similar. It is guaranteed that this directory is local and
 168         offers the greatest possible file system feature set the
 169         operating system provides. For further details, see the <ulink
 170         url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 171         Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
 172         is not set if the current user is not the original user of the session.</para></listitem>
 173       </varlistentry>
 174
 175     </variablelist>
 176
 177     <para>The following environment variables are read by the module and may be used by the PAM service to pass
 178     metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
 179     otherwise they are set by the module, so that these variables are initialized for the session and applications if
 180     known at all.</para>
 181
 182     <variablelist class='environment-variables'>
 183       <varlistentry>
 184         <term><varname>$XDG_SESSION_TYPE</varname></term>
 185
 186         <listitem><para>The session type. This may be used instead of <varname>session=</varname> on the module parameter
 187         line, and is usually preferred.</para></listitem>
 188       </varlistentry>
 189
 190       <varlistentry>
 191         <term><varname>$XDG_SESSION_CLASS</varname></term>
 192
 193         <listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
 194         line, and is usually preferred.</para></listitem>
 195       </varlistentry>
 196
 197       <varlistentry>
 198         <term><varname>$XDG_SESSION_DESKTOP</varname></term>
 199
 200         <listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
 201         parameter line, and is usually preferred.</para></listitem>
 202       </varlistentry>
 203
 204       <varlistentry>
 205         <term><varname>$XDG_SEAT</varname></term>
 206
 207         <listitem><para>The seat name the session shall be registered
 208         for, if any.</para></listitem>
 209       </varlistentry>
 210
 211       <varlistentry>
 212         <term><varname>$XDG_VTNR</varname></term>
 213
 214         <listitem><para>The VT number the session shall be registered
 215         for, if any. (Only applies to seats with a VT available, such
 216         as <literal>seat0</literal>)</para></listitem>
 217       </varlistentry>
 218     </variablelist>
 219
 220     <para>If not set, <command>pam_systemd</command> will initialize
 221     <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
 222     based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
 223   </refsect1>
 224
 225   <refsect1>
 226     <title>Session limits</title>
 227
 228     <para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
 229     can set session scope limits using the PAM context objects. The data for these objects is provided as NUL-terminated C strings
 230     and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
 231     they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
 232     which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
 233     by all the user's sessions, is not covered by these limits.
 234     </para>
 235
 236     <para> See
 237     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
 238     Also, see <citerefentry><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
 239     the context objects.
 240     </para>
 241
 242     <variablelist class='pam-directives'>
 243       <varlistentry>
 244         <term><varname>systemd.memory_max</varname></term>
 245
 246         <listitem><para>Sets unit <varname>MemoryMax=</varname>.</para></listitem>
 247       </varlistentry>
 248
 249       <varlistentry>
 250         <term><varname>systemd.tasks_max</varname></term>
 251
 252         <listitem><para>Sets unit <varname>TasksMax=</varname>.</para></listitem>
 253       </varlistentry>
 254
 255       <varlistentry>
 256         <term><varname>systemd.cpu_weight</varname></term>
 257
 258         <listitem><para>Sets unit <varname>CPUWeight=</varname>.</para></listitem>
 259       </varlistentry>
 260
 261       <varlistentry>
 262         <term><varname>systemd.io_weight</varname></term>
 263
 264         <listitem><para>Sets unit <varname>IOWeight=</varname>.</para></listitem>
 265       </varlistentry>
 266     </variablelist>
 267
 268     <para>Example data as can be provided from an another PAM module:
 269       <programlisting>
 270 pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
 271 pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
 272 pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
 273 pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
 274       </programlisting>
 275     </para>
 276
 277   </refsect1>
 278
 279   <refsect1>
 280     <title>Example</title>
 281
 282     <programlisting>#%PAM-1.0
 283 auth       required     pam_unix.so
 284 auth       required     pam_nologin.so
 285 account    required     pam_unix.so
 286 password   required     pam_unix.so
 287 session    required     pam_unix.so
 288 session    required     pam_loginuid.so
 289 session    required     pam_systemd.so</programlisting>
 290   </refsect1>
 291
 292   <refsect1>
 293     <title>See Also</title>
 294     <para>
 295       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 296       <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 297       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 298       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 299       <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 300       <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 301       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 302       <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 303       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 304       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 305       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 306     </para>
 307   </refsect1>
 308
 309 </refentry>