man/pam_systemd.xml

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   8
   9 <refentry id="pam_systemd" conditional='HAVE_PAM'>
  10
  11   <refentryinfo>
  12     <title>pam_systemd</title>
  13     <productname>systemd</productname>
  14   </refentryinfo>
  15
  16   <refmeta>
  17     <refentrytitle>pam_systemd</refentrytitle>
  18     <manvolnum>8</manvolnum>
  19   </refmeta>
  20
  21   <refnamediv>
  22     <refname>pam_systemd</refname>
  23     <refpurpose>Register user sessions in the systemd login manager</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <para><filename>pam_systemd.so</filename></para>
  28   </refsynopsisdiv>
  29
  30   <refsect1>
  31     <title>Description</title>
  32
  33     <para><command>pam_systemd</command> registers user sessions with
  34     the systemd login manager
  35     <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  36     and hence the systemd control group hierarchy.</para>
  37
  38     <para>On login, this module — in conjunction with <filename>systemd-logind.service</filename> — ensures the
  39     following:</para>
  40
  41     <orderedlist>
  42       <listitem><para>If it does not exist yet, the user runtime directory <filename>/run/user/$UID</filename> is
  43       either created or mounted as new <literal>tmpfs</literal> file system with quota applied, and its ownership
  44       changed to the user that is logging in.</para></listitem>
  45
  46       <listitem><para>The <varname>$XDG_SESSION_ID</varname> environment variable is initialized. If auditing is
  47       available and <command>pam_loginuid.so</command> was run before this module (which is highly recommended), the
  48       variable is initialized from the auditing session id (<filename>/proc/self/sessionid</filename>). Otherwise, an
  49       independent session counter is used.</para></listitem>
  50
  51       <listitem><para>A new systemd scope unit is created for the session. If this is the first concurrent session of
  52       the user, an implicit per-user slice unit below <filename>user.slice</filename> is automatically created and the
  53       scope placed into it. An instance of the system service <filename>user@.service</filename>, which runs the
  54       systemd user manager instance, is started.  </para></listitem>
  55     </orderedlist>
  56
  57     <para>On logout, this module ensures the following:</para>
  58
  59     <orderedlist>
  60       <listitem><para>If enabled in
  61       <citerefentry><refentrytitle>logind.conf</refentrytitle>
  62       <manvolnum>5</manvolnum></citerefentry> (<varname>KillUserProcesses=</varname>), all processes of the session are
  63       terminated. If the last concurrent session of a user ends, the user's systemd instance will be terminated too,
  64       and so will the user's slice unit.</para></listitem>
  65
  66       <listitem><para>If the last concurrent session of a user ends,
  67       the user runtime directory <filename>/run/user/$UID</filename> and all its
  68       contents are removed, too.</para></listitem>
  69     </orderedlist>
  70
  71     <para>If the system was not booted up with systemd as init system,
  72     this module does nothing and immediately returns
  73     <constant>PAM_SUCCESS</constant>.</para>
  74
  75   </refsect1>
  76
  77   <refsect1>
  78     <title>Options</title>
  79
  80     <para>The following options are understood:</para>
  81
  82     <variablelist class='pam-directives'>
  83
  84       <varlistentry>
  85         <term><varname>class=</varname></term>
  86
  87         <listitem><para>Takes a string argument which sets the session class. The <varname>XDG_SESSION_CLASS</varname>
  88         environment variable (see below) takes precedence. One of <literal>user</literal>, <literal>greeter</literal>,
  89         <literal>lock-screen</literal> or <literal>background</literal>. See
  90         <citerefentry><refentrytitle>sd_session_get_class</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
  91         details about the session class.</para></listitem>
  92       </varlistentry>
  93
  94       <varlistentry>
  95         <term><varname>type=</varname></term>
  96
  97         <listitem><para>Takes a string argument which sets the session type. The <varname>XDG_SESSION_TYPE</varname>
  98         environment variable (see below) takes precedence. One of <literal>unspecified</literal>,
  99         <literal>tty</literal>, <literal>x11</literal>, <literal>wayland</literal> or <literal>mir</literal>. See
 100         <citerefentry><refentrytitle>sd_session_get_type</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 101         details about the session type.</para></listitem>
 102       </varlistentry>
 103
 104       <varlistentry>
 105         <term><varname>desktop=</varname></term>
 106
 107         <listitem><para>Takes a single, short identifier string for the desktop environment. The
 108         <varname>XDG_SESSION_DESKTOP</varname> environment variable (see below) takes precedence. This may be used to
 109         indicate the session desktop used, where this applies and if this information is available. For example:
 110         <literal>GNOME</literal>, or <literal>KDE</literal>. It is recommended to use the same identifiers and
 111         capitalization as for <varname>$XDG_CURRENT_DESKTOP</varname>, as defined by the <ulink
 112         url="http://standards.freedesktop.org/desktop-entry-spec/latest/">Desktop Entry
 113         Specification</ulink>. (However, note that the option only takes a single item, and not a colon-separated list
 114         like <varname>$XDG_CURRENT_DESKTOP</varname>.) See
 115         <citerefentry><refentrytitle>sd_session_get_desktop</refentrytitle><manvolnum>3</manvolnum></citerefentry> for
 116         further details.</para></listitem>
 117       </varlistentry>
 118
 119       <varlistentry>
 120         <term><varname>debug</varname><optional>=</optional></term>
 121
 122         <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log
 123         debugging information as it operates.</para></listitem>
 124       </varlistentry>
 125     </variablelist>
 126   </refsect1>
 127
 128   <refsect1>
 129     <title>Module Types Provided</title>
 130
 131     <para>Only <option>session</option> is provided.</para>
 132   </refsect1>
 133
 134   <refsect1>
 135     <title>Environment</title>
 136
 137     <para>The following environment variables are initialized by the module and available to the processes of the
 138     user's session:</para>
 139
 140     <variablelist class='environment-variables'>
 141       <varlistentry>
 142         <term><varname>$XDG_SESSION_ID</varname></term>
 143
 144         <listitem><para>A short session identifier, suitable to be used in filenames. The string itself should be
 145         considered opaque, although often it is just the audit session ID as reported by
 146         <filename>/proc/self/sessionid</filename>. Each ID will be assigned only once during machine uptime. It may
 147         hence be used to uniquely label files or other resources of this session. Combine this ID with the boot
 148         identifier, as returned by
 149         <citerefentry><refentrytitle>sd_id128_get_boot</refentrytitle><manvolnum>3</manvolnum></citerefentry>, for a
 150         globally unique identifier for the current session.</para></listitem>
 151       </varlistentry>
 152
 153       <varlistentry>
 154         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 155
 156         <listitem><para>Path to a user-private user-writable directory
 157         that is bound to the user login time on the machine. It is
 158         automatically created the first time a user logs in and
 159         removed on the user's final logout. If a user logs in twice at
 160         the same time, both sessions will see the same
 161         <varname>$XDG_RUNTIME_DIR</varname> and the same contents. If
 162         a user logs in once, then logs out again, and logs in again,
 163         the directory contents will have been lost in between, but
 164         applications should not rely on this behavior and must be able
 165         to deal with stale files. To store session-private data in
 166         this directory, the user should include the value of
 167         <varname>$XDG_SESSION_ID</varname> in the filename. This
 168         directory shall be used for runtime file system objects such
 169         as <constant>AF_UNIX</constant> sockets, FIFOs, PID files and
 170         similar. It is guaranteed that this directory is local and
 171         offers the greatest possible file system feature set the
 172         operating system provides. For further details, see the <ulink
 173         url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG
 174         Base Directory Specification</ulink>. <varname>$XDG_RUNTIME_DIR</varname>
 175         is not set if the current user is not the original user of the session.</para></listitem>
 176       </varlistentry>
 177
 178     </variablelist>
 179
 180     <para>The following environment variables are read by the module and may be used by the PAM service to pass
 181     metadata to the module. If these variables are not set when the PAM module is invoked but can be determined
 182     otherwise they are set by the module, so that these variables are initialized for the session and applications if
 183     known at all.</para>
 184
 185     <variablelist class='environment-variables'>
 186       <varlistentry>
 187         <term><varname>$XDG_SESSION_TYPE</varname></term>
 188
 189         <listitem><para>The session type. This may be used instead of <varname>session=</varname> on the module parameter
 190         line, and is usually preferred.</para></listitem>
 191       </varlistentry>
 192
 193       <varlistentry>
 194         <term><varname>$XDG_SESSION_CLASS</varname></term>
 195
 196         <listitem><para>The session class. This may be used instead of <varname>class=</varname> on the module parameter
 197         line, and is usually preferred.</para></listitem>
 198       </varlistentry>
 199
 200       <varlistentry>
 201         <term><varname>$XDG_SESSION_DESKTOP</varname></term>
 202
 203         <listitem><para>The desktop identifier. This may be used instead of <varname>desktop=</varname> on the module
 204         parameter line, and is usually preferred.</para></listitem>
 205       </varlistentry>
 206
 207       <varlistentry>
 208         <term><varname>$XDG_SEAT</varname></term>
 209
 210         <listitem><para>The seat name the session shall be registered
 211         for, if any.</para></listitem>
 212       </varlistentry>
 213
 214       <varlistentry>
 215         <term><varname>$XDG_VTNR</varname></term>
 216
 217         <listitem><para>The VT number the session shall be registered
 218         for, if any. (Only applies to seats with a VT available, such
 219         as <literal>seat0</literal>)</para></listitem>
 220       </varlistentry>
 221     </variablelist>
 222
 223     <para>If not set, <command>pam_systemd</command> will initialize
 224     <varname>$XDG_SEAT</varname> and <varname>$XDG_VTNR</varname>
 225     based on the <varname>$DISPLAY</varname> variable (if the latter is set).</para>
 226   </refsect1>
 227
 228   <refsect1>
 229     <title>Session limits</title>
 230
 231     <para>PAM modules earlier in the stack, that is those that come before <command>pam_systemd.so</command>,
 232     can set session scope limits using the PAM context objects. The data for these objects is provided as NUL-terminated C strings
 233     and maps directly to the respective unit resource control directives. Note that these limits apply to individual sessions of the user,
 234     they do not apply to all user processes as a combined whole. In particular, the per-user <command>user@.service</command> unit instance,
 235     which runs the <command>systemd --user</command> manager process and its children, and is tracked outside of any session, being shared
 236     by all the user's sessions, is not covered by these limits.
 237     </para>
 238
 239     <para> See
 240     <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information about the resources.
 241     Also, see <citerefentry><refentrytitle>pam_set_data</refentrytitle><manvolnum>3</manvolnum></citerefentry> for additional information about how to set
 242     the context objects.
 243     </para>
 244
 245     <variablelist class='pam-directives'>
 246       <varlistentry>
 247         <term><varname>systemd.memory_max</varname></term>
 248
 249         <listitem><para>Sets unit <varname>MemoryMax=</varname>.</para></listitem>
 250       </varlistentry>
 251
 252       <varlistentry>
 253         <term><varname>systemd.tasks_max</varname></term>
 254
 255         <listitem><para>Sets unit <varname>TasksMax=</varname>.</para></listitem>
 256       </varlistentry>
 257
 258       <varlistentry>
 259         <term><varname>systemd.cpu_weight</varname></term>
 260
 261         <listitem><para>Sets unit <varname>CPUWeight=</varname>.</para></listitem>
 262       </varlistentry>
 263
 264       <varlistentry>
 265         <term><varname>systemd.io_weight</varname></term>
 266
 267         <listitem><para>Sets unit <varname>IOWeight=</varname>.</para></listitem>
 268       </varlistentry>
 269     </variablelist>
 270
 271     <para>Example data as can be provided from an another PAM module:
 272       <programlisting>
 273 pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
 274 pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
 275 pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
 276 pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
 277       </programlisting>
 278     </para>
 279
 280   </refsect1>
 281
 282   <refsect1>
 283     <title>Example</title>
 284
 285     <programlisting>#%PAM-1.0
 286 auth       required     pam_unix.so
 287 auth       required     pam_nologin.so
 288 account    required     pam_unix.so
 289 password   required     pam_unix.so
 290 session    required     pam_unix.so
 291 session    required     pam_loginuid.so
 292 session    required     pam_systemd.so</programlisting>
 293   </refsect1>
 294
 295   <refsect1>
 296     <title>See Also</title>
 297     <para>
 298       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 299       <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 300       <citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 301       <citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 302       <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 303       <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 304       <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 305       <citerefentry project='man-pages'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 306       <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 307       <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 308       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 309     </para>
 310   </refsect1>
 311
 312 </refentry>