man/pam_systemd.xml

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   6   This file is part of systemd.
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   8   Copyright 2010 Lennart Poettering
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  23
  24 <refentry id="pam_systemd">
  25
  26         <refentryinfo>
  27                 <title>pam_systemd</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>pam_systemd</refentrytitle>
  42                 <manvolnum>8</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>pam_systemd</refname>
  47                 <refpurpose>Register user sessions in the systemd control group hierarchy</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <cmdsynopsis>
  52                         <command>pam_systemd.so</command>
  53                 </cmdsynopsis>
  54         </refsynopsisdiv>
  55
  56         <refsect1>
  57                 <title>Description</title>
  58
  59                 <para><command>pam_systemd</command> registers user
  60                 sessions in the systemd control group
  61                 hierarchy.</para>
  62
  63                 <para>On login, this module ensures the following:</para>
  64
  65                 <orderedlist>
  66                         <listitem><para>If it does not exist yet, the
  67                         user runtime directory
  68                         <filename>/var/run/user/$USER</filename> is
  69                         created and its ownership changed to the user
  70                         that is logging in.</para></listitem>
  71
  72                         <listitem><para>If
  73                         <option>create-session=1</option> is set, the
  74                         <varname>$XDG_SESSION_ID</varname> environment
  75                         variable is initialized. If auditing is
  76                         available and
  77                         <command>pam_loginuid.so</command> run before
  78                         this module (which is highly recommended), the
  79                         variable is initialized from the auditing
  80                         session id
  81                         (<filename>/proc/self/sessionid</filename>). Otherwise
  82                         an independent session counter is
  83                         used.</para></listitem>
  84
  85                         <listitem><para>If
  86                         <option>create-session=1</option> is set, a new
  87                         control group
  88                         <filename>/user/$USER/$XDG_SESSION_ID</filename>
  89                         is created and the login process moved into
  90                         it.</para></listitem>
  91
  92                         <listitem><para>If
  93                         <option>create-session=0</option> is set, a new
  94                         control group
  95                         <filename>/user/$USER/user</filename>
  96                         is created and the login process moved into
  97                         it.</para></listitem>
  98
  99                 </orderedlist>
 100
 101                 <para>On logout, this module ensures the following:</para>
 102
 103                 <orderedlist>
 104                         <listitem><para>If
 105                         <varname>$XDG_SESSION_ID</varname> is set and
 106                         <option>kill-session=1</option> specified, all
 107                         remaining processes in the
 108                         <filename>/user/$USER/$XDG_SESSION_ID</filename>
 109                         control group are killed and the control group
 110                         is removed.</para></listitem>
 111
 112                         <listitem><para>If
 113                         <varname>$XDG_SESSION_ID</varname> is set and
 114                         <option>kill-session=0</option> specified, all
 115                         remaining processes in the
 116                         <filename>/user/$USER/$XDG_SESSION_ID</filename>
 117                         control group are migrated to
 118                         <filename>/user/$USER/user</filename> and
 119                         the original control group is
 120                         removed.</para></listitem>
 121
 122                         <listitem><para>If
 123                         <option>kill-user=1</option> is specified, and
 124                         no other user session control group remains,
 125                         except
 126                         <filename>/user/$USER/user</filename>,
 127                         all remaining processes in the
 128                         <filename>/user/$USER</filename> hierarchy
 129                         are killed and the control group is removed.</para></listitem>
 130
 131                         <listitem><para>If
 132                         <option>kill-user=0</option> is specified, and
 133                         no process remains in the
 134                         <filename>/user/$USER</filename> hierarchy the
 135                         control group is removed.</para></listitem>
 136
 137                         <listitem><para>If the
 138                         <filename>/user/$USER</filename> control group
 139                         was removed the
 140                         <varname>$XDG_RUNTIME_DIR</varname> directory
 141                         and all its contents are
 142                         removed, too.</para></listitem>
 143                 </orderedlist>
 144
 145                 <para>If the system was not booted up with systemd as
 146                 init system, this module does nothing and immediately
 147                 returns PAM_SUCCESS.</para>
 148
 149         </refsect1>
 150
 151         <refsect1>
 152                 <title>Options</title>
 153
 154                 <para>The following options are understood:</para>
 155
 156                 <variablelist>
 157                         <varlistentry>
 158                                 <term><option>create-session=</option></term>
 159
 160                                 <listitem><para>Takes a boolean
 161                                 argument. If true, a new session is
 162                                 created: the
 163                                 <varname>$XDG_SESSION_ID</varname>
 164                                 environment variable is set and the
 165                                 login process moved to the
 166                                 <filename>/user/$USER/$XDG_SESSION_ID</filename>
 167                                 control group. It is recommended that
 168                                 all services which are directly created
 169                                 on the user's behalf set this
 170                                 option. Only for services that shall
 171                                 automatically be terminated when the
 172                                 user logs out completely, otherwise
 173                                 <varname>create-session=0</varname>
 174                                 should be set.</para></listitem>
 175                         </varlistentry>
 176
 177                         <varlistentry>
 178                                 <term><option>kill-session=</option></term>
 179
 180                                 <listitem><para>Takes a boolean
 181                                 argument. If true, all processes
 182                                 created by the user during his session
 183                                 and from his session will be
 184                                 terminated when he logs out from his
 185                                 session.</para></listitem>
 186                         </varlistentry>
 187
 188                         <varlistentry>
 189                                 <term><option>kill-user=</option></term>
 190
 191                                 <listitem><para>Takes a boolean
 192                                 argument. If true, all processes
 193                                 created by the user during his session
 194                                 and from his session will be
 195                                 terminated after he logged out
 196                                 completely. This is a weaker version
 197                                 of <option>kill-session=1</option> and is
 198                                 more friendly for users logged in more
 199                                 than once, as their processes are
 200                                 terminated only on their complete
 201                                 logout.</para></listitem>
 202                         </varlistentry>
 203
 204                         <varlistentry>
 205                                 <term><option>keep-root=</option></term>
 206
 207                                 <listitem><para>Takes a boolean
 208                                 argument. If true, all processes
 209                                 created by the root user (UID 0) during his
 210                                 session and from his session will be
 211                                 kept around after he logged out. This
 212                                 option allows cancelling the effect of
 213                                 <option>kill-session=1</option> and
 214                                 <option>kill-user=1</option> for the
 215                                 root user.</para></listitem>
 216                         </varlistentry>
 217
 218                         <varlistentry>
 219                                 <term><option>controllers=</option></term>
 220
 221                                 <listitem><para>Takes a comma
 222                                 separated list of cgroup controllers
 223                                 in which hierarchies a user/session
 224                                 cgroup will be created by default for
 225                                 each user logging in. If ommited,
 226                                 defaults to 'cpu', meaning that in
 227                                 addition to creating per-user and
 228                                 per-session cgroups in systemd's own
 229                                 hierarchy, groups are created in the
 230                                 'cpu' hierarchy, on order to ensure
 231                                 that every use and every sessions gets
 232                                 an equal amount of CPU time,
 233                                 regardless how many processes a user
 234                                 or session might
 235                                 own.</para></listitem>
 236                         </varlistentry>
 237                 </variablelist>
 238
 239                 <para>Note that setting <varname>kill-user=1</varname>
 240                 or even <varname>kill-session=1</varname> will break
 241                 tools like
 242                 <citerefentry><refentrytitle>screen</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
 243
 244                 <para>If the options are omitted they default to
 245                 <option>create-session=1</option>,
 246                 <option>kill-session=0</option>,
 247                 <option>kill-user=0</option>,
 248                 <option>keep-root=1</option>.</para>
 249         </refsect1>
 250
 251         <refsect1>
 252                 <title>Module Types Provided</title>
 253
 254                 <para>Only <option>session</option> is provided.</para>
 255         </refsect1>
 256
 257         <refsect1>
 258                 <title>Environment</title>
 259
 260                 <para>The following environment variables are set for the processes of the user's session:</para>
 261
 262                 <variablelist>
 263                         <varlistentry>
 264                                 <term><varname>$XDG_SESSION_ID</varname></term>
 265
 266                                 <listitem><para>A session identifier,
 267                                 suitable to be used in file names. The
 268                                 string itself should be considered
 269                                 opaque, although often it is just the
 270                                 audit session ID as reported by
 271                                 <filename>/proc/self/sessionid</filename>. Each
 272                                 ID will be assigned only once during
 273                                 machine uptime. It may hence be used
 274                                 to uniquely label files or other
 275                                 resources of this
 276                                 session.</para></listitem>
 277                         </varlistentry>
 278
 279                         <varlistentry>
 280                                 <term><varname>$XDG_RUNTIME_DIR</varname></term>
 281
 282                                 <listitem><para>Path to a user-private
 283                                 user-writable directory that is bound
 284                                 to the user login time on the
 285                                 machine. It is automatically created
 286                                 the first time a user logs in and
 287                                 removed on his final logout. If a user
 288                                 logs in twice at the same time, both
 289                                 sessions will see the same
 290                                 <varname>$XDG_RUNTIME_DIR</varname>
 291                                 and the same contents. If a user logs
 292                                 in once, then logs out again, and logs
 293                                 in again, the directory contents will
 294                                 have been lost in between, but
 295                                 applications should not rely on this
 296                                 behaviour and must be able to deal with
 297                                 stale files. To store session-private
 298                                 data in this directory the user should
 299                                 include the value of <varname>$XDG_SESSION_ID</varname>
 300                                 in the filename. This directory shall
 301                                 be used for runtime file system
 302                                 objects such as AF_UNIX sockets,
 303                                 FIFOs, PID files and similar. It is
 304                                 guaranteed that this directory is
 305                                 local and offers the greatest possible
 306                                 file system feature set the
 307                                 operating system
 308                                 provides.</para></listitem>
 309                         </varlistentry>
 310                 </variablelist>
 311         </refsect1>
 312
 313         <refsect1>
 314                 <title>Example</title>
 315
 316                 <programlisting>#%PAM-1.0
 317 auth       required     pam_unix.so
 318 auth       required     pam_nologin.so
 319 account    required     pam_unix.so
 320 password   required     pam_unix.so
 321 session    required     pam_unix.so
 322 session    required     pam_loginuid.so
 323 session    required     pam_systemd.so kill-user=1</programlisting>
 324         </refsect1>
 325
 326         <refsect1>
 327                 <title>See Also</title>
 328                 <para>
 329                         <citerefentry><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 330                         <citerefentry><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 331                         <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 332                         <citerefentry><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 333                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 334                 </para>
 335         </refsect1>
 336
 337 </refentry>