man/pam_systemd.xml

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   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 <varname>XDG_SESSION_CLASS</varname>
  94         environment variable (see below) takes precedence. One of <literal>user</literal>, <literal>greeter</literal>,
  95         <literal>lock-screen</literal> or <literal>background</literal>. See
  96         <citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  97         details about the session class.</para>
  98
  99         <xi:include href="version-info.xml" xpointer="v197"/></listitem>
 100       </varlistentry>
 101
 102       <varlistentry>
 103         <term><varname>type=</varname></term>
 104
 105         <listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
 106         environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
 107         <literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
 108         <citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 109         details about the session type.</para>
 110
 111         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 112       </varlistentry>
 113
 114       <varlistentry>
 115         <term><varname>desktop=</varname></term>
 116
 117         <listitem><para>Takes a single, short identifier string for the desktop environment. The
 118         <varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
 119         indicate the session desktop used, where this applies and if this information is available. For example:
 120         <literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
 121         capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
 122         url="https://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
 123         Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
 124         like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
 125         <citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 126         further details.</para>
 127
 128         <xi:include href="version-info.xml" xpointer="v240"/></listitem>
 129       </varlistentry>
 130
 131       <varlistentry>
 132         <term><varname>default-capability-bounding-set=</varname></term>
 133         <term><varname>default-capability-ambient-set=</varname></term>
 134
 135         <listitem><para>Takes a comma-separated list of process capabilities
 136         (e.g. <constant>CAP_WAKE_ALARM</constant>, <constant>CAP_BLOCK_SUSPEND</constant>, …) to set for the
 137         invoked session's processes, if the user record does not encode appropriate sets of capabilities
 138         directly. See <citerefentry
 139         project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 140         for details on the capabilities concept. If not specified, the default bounding set is left as is
 141         (i.e. usually contains the full set of capabilities). The default ambient set is set to
 142         <constant>CAP_WAKE_ALARM</constant> for regular users if the PAM session is associated with a local
 143         seat or if it is invoked for the <literal>systemd-user</literal> service. Otherwise defaults to the
 144         empty set.</para>
 145
 146         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 147       </varlistentry>
 148
 149       <varlistentry>
 150         <term><varname>debug</varname><optional>=</optional></term>
 151
 152         <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
 153         debugging information as it operates.</para></listitem>
 154       </varlistentry>
 155     </variablelist>
 156   </refsect1>
 157
 158   <refsect1>
 159     <title>Module Types Provided</title>
 160
 161     <para>Only <option>session</option> is provided.</para>
 162   </refsect1>
 163
 164   <refsect1>
 165     <title>Environment</title>
 166
 167     <para>The following environment variables are initialized by the module and available to the processes of the
 168     user's session:</para>
 169
 170     <variablelist class='environment-variables'>
 171       <varlistentry>
 172         <term><varname>$XDG_SESSION_ID</varname></term>
 173
 174         <listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
 175         considered opaque, although often it is just the audit session ID as reported by
 176         <filename>/proc/self/sessionid</filename>. Each ID will be assigned only once during machine uptime. It may
 177         hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
 178         identifier, as returned by
 179         <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
 180         globally unique identifier.</para></listitem>
 181       </varlistentry>
 182
 183       <varlistentry>
 184         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 185
 186         <listitem><para>Path to a user-private user-writable directory
 187         that is bound to the user login time on the machine. It is
 188         automatically created the first time a user logs in and
 189         removed on the user's final logout. If a user logs in twice at
 190         the same time, both sessions will see the same
 191         <varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
 192         a user logs in once, then logs out again, and logs in again,
 193         the directory contents will have been lost in between, but
 194         applications should not rely on this behavior and must be able
 195         to deal with stale files. To store session-private data in
 196         this directory, the user should include the value of
 197         <varname>$XDG_SESSION_ID</varname> in the filename. This
 198         directory shall be used for runtime file system objects such
 199         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
 200         similar. It is guaranteed that this directory is local and
 201         offers the greatest possible file system feature set the
 202         operating system provides. For further details, see the <ulink
 203         url="https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 204         Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
 205         is not set if the current user is not the original user of the session.</para></listitem>
 206       </varlistentry>
 207
 208       <varlistentry>
 209         <term><varname>$TZ</varname></term>
 210         <term><varname>$EMAIL</varname></term>
 211         <term><varname>$LANG</varname></term>
 212
 213         <listitem><para>If a JSON user record is known for the user logging in these variables are
 214         initialized from the respective data in the record.</para>
 215
 216         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 217       </varlistentry>
 218
 219     </variablelist>
 220
 221     <para>The following environment variables are read by the module and may be used by the PAM service to pass
 222     metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
 223     otherwise they are set by the module, so that these variables are initialized for the session and applications if
 224     known at all.</para>
 225
 226     <variablelist class='environment-variables'>
 227       <varlistentry>
 228         <term><varname>$XDG_SESSION_TYPE</varname></term>
 229
 230         <listitem><para>The session type. This may be used instead of <varname>type=</varname> on the module parameter
 231         line, and is usually preferred.</para>
 232
 233         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 234       </varlistentry>
 235
 236       <varlistentry>
 237         <term><varname>$XDG_SESSION_CLASS</varname></term>
 238
 239         <listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
 240         line, and is usually preferred.</para>
 241
 242         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 243       </varlistentry>
 244
 245       <varlistentry>
 246         <term><varname>$XDG_SESSION_DESKTOP</varname></term>
 247
 248         <listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
 249         parameter line, and is usually preferred.</para>
 250
 251         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 252       </varlistentry>
 253
 254       <varlistentry>
 255         <term><varname>$XDG_SEAT</varname></term>
 256
 257         <listitem><para>The seat name the session shall be registered
 258         for, if any.</para>
 259
 260         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 261       </varlistentry>
 262
 263       <varlistentry>
 264         <term><varname>$XDG_VTNR</varname></term>
 265
 266         <listitem><para>The VT number the session shall be registered
 267         for, if any. (Only applies to seats with a VT available, such
 268         as <literal>seat0</literal>)</para>
 269
 270         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 271       </varlistentry>
 272     </variablelist>
 273
 274     <para>If not set, <command>pam_systemd</command> will initialize
 275     <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
 276     based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
 277   </refsect1>
 278
 279   <refsect1>
 280     <title>Session limits</title>
 281
 282     <para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
 283     can set session scope limits using the PAM context objects. The data for these objects is provided as <constant>NUL</constant>-terminated C strings
 284     and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
 285     they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
 286     which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
 287     by all the user's sessions, is not covered by these limits.
 288     </para>
 289
 290     <para> See
 291     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
 292     Also, see <citerefentry project='man-pages'><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
 293     the context objects.
 294     </para>
 295
 296     <variablelist class='pam-directives'>
 297       <varlistentry>
 298         <term><varname>systemd.memory_max=</varname></term>
 299
 300         <listitem><para>Sets unit <varname>MemoryMax=</varname>.</para>
 301
 302         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 303       </varlistentry>
 304
 305       <varlistentry>
 306         <term><varname>systemd.tasks_max=</varname></term>
 307
 308         <listitem><para>Sets unit <varname>TasksMax=</varname>.</para>
 309
 310         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 311       </varlistentry>
 312
 313       <varlistentry>
 314         <term><varname>systemd.cpu_weight=</varname></term>
 315
 316         <listitem><para>Sets unit <varname>CPUWeight=</varname>.</para>
 317
 318         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 319       </varlistentry>
 320
 321       <varlistentry>
 322         <term><varname>systemd.io_weight=</varname></term>
 323
 324         <listitem><para>Sets unit <varname>IOWeight=</varname>.</para>
 325
 326         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 327       </varlistentry>
 328
 329       <varlistentry>
 330         <term><varname>systemd.runtime_max_sec=</varname></term>
 331
 332         <listitem><para>Sets unit <varname>RuntimeMaxSec=</varname>.</para>
 333
 334         <xi:include href="version-info.xml" xpointer="v246"/></listitem>
 335       </varlistentry>
 336     </variablelist>
 337
 338     <para>Example data as can be provided from an another PAM module:
 339       <programlisting>
 340 pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
 341 pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
 342 pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
 343 pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
 344 pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);
 345       </programlisting>
 346     </para>
 347
 348   </refsect1>
 349
 350   <refsect1>
 351     <title>Example</title>
 352
 353     <para>Here's an example PAM configuration fragment that allows users sessions to be managed by
 354     <filename>systemd-logind.service</filename>:</para>
 355
 356     <programlisting>#%PAM-1.0
 357 auth      sufficient pam_unix.so
 358 -auth     sufficient pam_systemd_home.so
 359 auth      required   pam_deny.so
 360
 361 account   required   pam_nologin.so
 362 -account  sufficient pam_systemd_home.so
 363 account   sufficient pam_unix.so
 364 account   required   pam_permit.so
 365
 366 -password sufficient pam_systemd_home.so
 367 password  sufficient pam_unix.so sha512 shadow try_first_pass use_authtok
 368
 369 password  required   pam_deny.so
 370
 371 -session  optional   pam_keyinit.so revoke
 372 -session  optional   pam_loginuid.so
 373 -session  optional   pam_systemd_home.so
 374 <command>-session  optional   pam_systemd.so</command>
 375 session   required   pam_unix.so</programlisting>
 376   </refsect1>
 377
 378   <refsect1>
 379     <title>See Also</title>
 380     <para>
 381       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 382       <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 383       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 384       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 385       <citerefentry><refentrytitle>pam_systemd_home</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 386       <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 387       <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 388       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 389       <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 390       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 391       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 392       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 393     </para>
 394   </refsect1>
 395
 396 </refentry>