man/systemd.exec.xml

   1 <?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd.exec">
  25         <refentryinfo>
  26                 <title>systemd.exec</title>
  27                 <productname>systemd</productname>
  28
  29                 <authorgroup>
  30                         <author>
  31                                 <contrib>Developer</contrib>
  32                                 <firstname>Lennart</firstname>
  33                                 <surname>Poettering</surname>
  34                                 <email>lennart@poettering.net</email>
  35                         </author>
  36                 </authorgroup>
  37         </refentryinfo>
  38
  39         <refmeta>
  40                 <refentrytitle>systemd.exec</refentrytitle>
  41                 <manvolnum>5</manvolnum>
  42         </refmeta>
  43
  44         <refnamediv>
  45                 <refname>systemd.exec</refname>
  46                 <refpurpose>Execution environment configuration</refpurpose>
  47         </refnamediv>
  48
  49         <refsynopsisdiv>
  50                 <para><filename><replaceable>service</replaceable>.service</filename>,
  51                 <filename><replaceable>socket</replaceable>.socket</filename>,
  52                 <filename><replaceable>mount</replaceable>.mount</filename>,
  53                 <filename><replaceable>swap</replaceable>.swap</filename></para>
  54         </refsynopsisdiv>
  55
  56         <refsect1>
  57                 <title>Description</title>
  58
  59                 <para>Unit configuration files for services, sockets,
  60                 mount points, and swap devices share a subset of
  61                 configuration options which define the execution
  62                 environment of spawned processes.</para>
  63
  64                 <para>This man page lists the configuration options
  65                 shared by these four unit types. See
  66                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  67                 for the common options of all unit configuration
  68                 files, and
  69                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  70                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  71                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  72                 and
  73                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  74                 for more information on the specific unit
  75                 configuration files. The execution specific
  76                 configuration options are configured in the [Service],
  77                 [Socket], [Mount], or [Swap] sections, depending on the unit
  78                 type.</para>
  79         </refsect1>
  80
  81         <refsect1>
  82                 <title>Options</title>
  83
  84                 <variablelist class='unit-directives'>
  85
  86                         <varlistentry>
  87                                 <term><varname>WorkingDirectory=</varname></term>
  88
  89                                 <listitem><para>Takes an absolute
  90                                 directory path. Sets the working
  91                                 directory for executed processes. If
  92                                 not set, defaults to the root directory
  93                                 when systemd is running as a system
  94                                 instance and the respective user's
  95                                 home directory if run as
  96                                 user.</para></listitem>
  97                         </varlistentry>
  98
  99                         <varlistentry>
 100                                 <term><varname>RootDirectory=</varname></term>
 101
 102                                 <listitem><para>Takes an absolute
 103                                 directory path. Sets the root
 104                                 directory for executed processes, with
 105                                 the
 106                                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 107                                 system call. If this is used, it must
 108                                 be ensured that the process and all
 109                                 its auxiliary files are available in
 110                                 the <function>chroot()</function>
 111                                 jail.</para></listitem>
 112                         </varlistentry>
 113
 114                         <varlistentry>
 115                                 <term><varname>User=</varname></term>
 116                                 <term><varname>Group=</varname></term>
 117
 118                                 <listitem><para>Sets the Unix user
 119                                 or group that the processes are executed
 120                                 as, respectively. Takes a single user or group
 121                                 name or ID as argument. If no group is
 122                                 set, the default group of the user is
 123                                 chosen.</para></listitem>
 124                         </varlistentry>
 125
 126                         <varlistentry>
 127                                 <term><varname>SupplementaryGroups=</varname></term>
 128
 129                                 <listitem><para>Sets the supplementary
 130                                 Unix groups the processes are executed
 131                                 as. This takes a space-separated list
 132                                 of group names or IDs. This option may
 133                                 be specified more than once in which
 134                                 case all listed groups are set as
 135                                 supplementary groups. When the empty
 136                                 string is assigned the list of
 137                                 supplementary groups is reset, and all
 138                                 assignments prior to this one will
 139                                 have no effect. In any way, this
 140                                 option does not override, but extends
 141                                 the list of supplementary groups
 142                                 configured in the system group
 143                                 database for the
 144                                 user.</para></listitem>
 145                         </varlistentry>
 146
 147                         <varlistentry>
 148                                 <term><varname>Nice=</varname></term>
 149
 150                                 <listitem><para>Sets the default nice
 151                                 level (scheduling priority) for
 152                                 executed processes. Takes an integer
 153                                 between -20 (highest priority) and 19
 154                                 (lowest priority). See
 155                                 <citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 156                                 for details.</para></listitem>
 157                         </varlistentry>
 158
 159                         <varlistentry>
 160                                 <term><varname>OOMScoreAdjust=</varname></term>
 161
 162                                 <listitem><para>Sets the adjustment
 163                                 level for the Out-Of-Memory killer for
 164                                 executed processes. Takes an integer
 165                                 between -1000 (to disable OOM killing
 166                                 for this process) and 1000 (to make
 167                                 killing of this process under memory
 168                                 pressure very likely). See <ulink
 169                                 url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
 170                                 for details.</para></listitem>
 171                         </varlistentry>
 172
 173                         <varlistentry>
 174                                 <term><varname>IOSchedulingClass=</varname></term>
 175
 176                                 <listitem><para>Sets the IO scheduling
 177                                 class for executed processes. Takes an
 178                                 integer between 0 and 3 or one of the
 179                                 strings <option>none</option>,
 180                                 <option>realtime</option>,
 181                                 <option>best-effort</option> or
 182                                 <option>idle</option>. See
 183                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 184                                 for details.</para></listitem>
 185                         </varlistentry>
 186
 187                         <varlistentry>
 188                                 <term><varname>IOSchedulingPriority=</varname></term>
 189
 190                                 <listitem><para>Sets the IO scheduling
 191                                 priority for executed processes. Takes
 192                                 an integer between 0 (highest
 193                                 priority) and 7 (lowest priority). The
 194                                 available priorities depend on the
 195                                 selected IO scheduling class (see
 196                                 above). See
 197                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 198                                 for details.</para></listitem>
 199                         </varlistentry>
 200
 201                         <varlistentry>
 202                                 <term><varname>CPUSchedulingPolicy=</varname></term>
 203
 204                                 <listitem><para>Sets the CPU
 205                                 scheduling policy for executed
 206                                 processes. Takes one of
 207                                 <option>other</option>,
 208                                 <option>batch</option>,
 209                                 <option>idle</option>,
 210                                 <option>fifo</option> or
 211                                 <option>rr</option>. See
 212                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 213                                 for details.</para></listitem>
 214                         </varlistentry>
 215
 216                         <varlistentry>
 217                                 <term><varname>CPUSchedulingPriority=</varname></term>
 218
 219                                 <listitem><para>Sets the CPU
 220                                 scheduling priority for executed
 221                                 processes. The available priority
 222                                 range depends on the selected CPU
 223                                 scheduling policy (see above). For
 224                                 real-time scheduling policies an
 225                                 integer between 1 (lowest priority)
 226                                 and 99 (highest priority) can be used.
 227                                 See <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 228                                 for details.
 229                                 </para></listitem>
 230                         </varlistentry>
 231
 232                         <varlistentry>
 233                                 <term><varname>CPUSchedulingResetOnFork=</varname></term>
 234
 235                                 <listitem><para>Takes a boolean
 236                                 argument. If true, elevated CPU
 237                                 scheduling priorities and policies
 238                                 will be reset when the executed
 239                                 processes fork, and can hence not leak
 240                                 into child processes. See
 241                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 242                                 for details. Defaults to false.</para></listitem>
 243                         </varlistentry>
 244
 245                         <varlistentry>
 246                                 <term><varname>CPUAffinity=</varname></term>
 247
 248                                 <listitem><para>Controls the CPU
 249                                 affinity of the executed
 250                                 processes. Takes a space-separated
 251                                 list of CPU indexes. This option may
 252                                 be specified more than once in which
 253                                 case the specificed CPU affinity masks
 254                                 are merged. If the empty string is
 255                                 assigned, the mask is reset, all
 256                                 assignments prior to this will have no
 257                                 effect. See
 258                                 <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 259                                 for details.</para></listitem>
 260                         </varlistentry>
 261
 262                         <varlistentry>
 263                                 <term><varname>UMask=</varname></term>
 264
 265                                 <listitem><para>Controls the file mode
 266                                 creation mask. Takes an access mode in
 267                                 octal notation. See
 268                                 <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 269                                 for details. Defaults to
 270                                 0022.</para></listitem>
 271                         </varlistentry>
 272
 273                         <varlistentry>
 274                                 <term><varname>Environment=</varname></term>
 275
 276                                 <listitem><para>Sets environment
 277                                 variables for executed
 278                                 processes. Takes a space-separated
 279                                 list of variable assignments. This
 280                                 option may be specified more than once
 281                                 in which case all listed variables
 282                                 will be set. If the same variable is
 283                                 set twice, the later setting will
 284                                 override the earlier setting. If the
 285                                 empty string is assigned to this
 286                                 option, the list of environment
 287                                 variables is reset, all prior
 288                                 assignments have no effect.
 289                                 Variable expansion is not performed
 290                                 inside the strings, however, specifier
 291                                 expansion is possible. The $ character has
 292                                 no special meaning.
 293                                 If you need to assign a value containing spaces
 294                                 to a variable, use double quotes (")
 295                                 for the assignment.</para>
 296
 297                                 <para>Example:
 298                                 <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=word 5 6"</programlisting>
 299                                 gives three variables <literal>VAR1</literal>,
 300                                 <literal>VAR2</literal>, <literal>VAR3</literal>.
 301                                 </para>
 302
 303                                 <para>
 304                                 See
 305                                 <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 306                                 for details about environment variables.</para></listitem>
 307                         </varlistentry>
 308                         <varlistentry>
 309                                 <term><varname>EnvironmentFile=</varname></term>
 310                                 <listitem><para>Similar to
 311                                 <varname>Environment=</varname> but
 312                                 reads the environment variables from a
 313                                 text file. The text file should
 314                                 contain new-line-separated variable
 315                                 assignments. Empty lines and lines
 316                                 starting with ; or # will be ignored,
 317                                 which may be used for commenting. A line
 318                                 ending with a backslash will be concatenated
 319                                 with the following one, allowing multiline variable
 320                                 definitions. The parser strips leading
 321                                 and trailing whitespace from the values
 322                                 of assignments, unless you use
 323                                 double quotes (").</para>
 324
 325                                 <para>The argument passed should be an
 326                                 absolute filename or wildcard
 327                                 expression, optionally prefixed with
 328                                 <literal>-</literal>, which indicates
 329                                 that if the file does not exist, it
 330                                 will not be read and no error or warning
 331                                 message is logged.  This option may be
 332                                 specified more than once in which case
 333                                 all specified files are read. If the
 334                                 empty string is assigned to this
 335                                 option, the list of file to read is
 336                                 reset, all prior assignments have no
 337                                 effect.</para>
 338
 339                                 <para>The files listed with this
 340                                 directive will be read shortly before
 341                                 the process is executed. Settings from
 342                                 these files override settings made
 343                                 with
 344                                 <varname>Environment=</varname>. If
 345                                 the same variable is set twice from
 346                                 these files, the files will be read in
 347                                 the order they are specified and the
 348                                 later setting will override the
 349                                 earlier setting.</para></listitem>
 350                         </varlistentry>
 351
 352                         <varlistentry>
 353                                 <term><varname>StandardInput=</varname></term>
 354                                 <listitem><para>Controls where file
 355                                 descriptor 0 (STDIN) of the executed
 356                                 processes is connected to. Takes one
 357                                 of <option>null</option>,
 358                                 <option>tty</option>,
 359                                 <option>tty-force</option>,
 360                                 <option>tty-fail</option> or
 361                                 <option>socket</option>. If
 362                                 <option>null</option> is selected,
 363                                 standard input will be connected to
 364                                 <filename>/dev/null</filename>,
 365                                 i.e. all read attempts by the process
 366                                 will result in immediate EOF. If
 367                                 <option>tty</option> is selected,
 368                                 standard input is connected to a TTY
 369                                 (as configured by
 370                                 <varname>TTYPath=</varname>, see
 371                                 below) and the executed process
 372                                 becomes the controlling process of the
 373                                 terminal. If the terminal is already
 374                                 being controlled by another process, the
 375                                 executed process waits until the current
 376                                 controlling process releases the
 377                                 terminal.
 378                                 <option>tty-force</option>
 379                                 is similar to <option>tty</option>,
 380                                 but the executed process is forcefully
 381                                 and immediately made the controlling
 382                                 process of the terminal, potentially
 383                                 removing previous controlling
 384                                 processes from the
 385                                 terminal. <option>tty-fail</option> is
 386                                 similar to <option>tty</option> but if
 387                                 the terminal already has a controlling
 388                                 process start-up of the executed
 389                                 process fails.  The
 390                                 <option>socket</option> option is only
 391                                 valid in socket-activated services,
 392                                 and only when the socket configuration
 393                                 file (see
 394                                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 395                                 for details) specifies a single socket
 396                                 only. If this option is set, standard
 397                                 input will be connected to the socket
 398                                 the service was activated from, which
 399                                 is primarily useful for compatibility
 400                                 with daemons designed for use with the
 401                                 traditional
 402                                 <citerefentry><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 403                                 daemon. This setting defaults to
 404                                 <option>null</option>.</para></listitem>
 405                         </varlistentry>
 406                         <varlistentry>
 407                                 <term><varname>StandardOutput=</varname></term>
 408                                 <listitem><para>Controls where file
 409                                 descriptor 1 (STDOUT) of the executed
 410                                 processes is connected to. Takes one
 411                                 of <option>inherit</option>,
 412                                 <option>null</option>,
 413                                 <option>tty</option>,
 414                                 <option>syslog</option>,
 415                                 <option>kmsg</option>,
 416                                 <option>journal</option>,
 417                                 <option>syslog+console</option>,
 418                                 <option>kmsg+console</option>,
 419                                 <option>journal+console</option> or
 420                                 <option>socket</option>. If set to
 421                                 <option>inherit</option>, the file
 422                                 descriptor of standard input is
 423                                 duplicated for standard output. If set
 424                                 to <option>null</option>, standard
 425                                 output will be connected to
 426                                 <filename>/dev/null</filename>,
 427                                 i.e. everything written to it will be
 428                                 lost. If set to <option>tty</option>,
 429                                 standard output will be connected to a
 430                                 tty (as configured via
 431                                 <varname>TTYPath=</varname>, see
 432                                 below). If the TTY is used for output
 433                                 only, the executed process will not
 434                                 become the controlling process of the
 435                                 terminal, and will not fail or wait
 436                                 for other processes to release the
 437                                 terminal. <option>syslog</option>
 438                                 connects standard output to the
 439                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 440                                 system syslog
 441                                 service. <option>kmsg</option>
 442                                 connects it with the kernel log buffer
 443                                 which is accessible via
 444                                 <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>journal</option>
 445                                 connects it with the journal which is
 446                                 accessible via
 447                                 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 448                                 (Note that everything that is written
 449                                 to syslog or kmsg is implicitly stored
 450                                 in the journal as well, those options
 451                                 are hence supersets of this
 452                                 one). <option>syslog+console</option>,
 453                                 <option>journal+console</option> and
 454                                 <option>kmsg+console</option> work
 455                                 similarly but copy the output to the
 456                                 system console as
 457                                 well. <option>socket</option> connects
 458                                 standard output to a socket from
 459                                 socket activation, semantics are
 460                                 similar to the respective option of
 461                                 <varname>StandardInput=</varname>.
 462                                 This setting defaults to the value set
 463                                 with
 464                                 <option>DefaultStandardOutput=</option>
 465                                 in
 466                                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 467                                 which defaults to
 468                                 <option>journal</option>.</para></listitem>
 469                         </varlistentry>
 470                         <varlistentry>
 471                                 <term><varname>StandardError=</varname></term>
 472                                 <listitem><para>Controls where file
 473                                 descriptor 2 (STDERR) of the executed
 474                                 processes is connected to. The
 475                                 available options are identical to
 476                                 those of
 477                                 <varname>StandardOutput=</varname>,
 478                                 with one exception: if set to
 479                                 <option>inherit</option> the file
 480                                 descriptor used for standard output is
 481                                 duplicated for standard error. This
 482                                 setting defaults to the value set with
 483                                 <option>DefaultStandardError=</option>
 484                                 in
 485                                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 486                                 which defaults to
 487                                 <option>inherit</option>.</para></listitem>
 488                         </varlistentry>
 489                         <varlistentry>
 490                                 <term><varname>TTYPath=</varname></term>
 491                                 <listitem><para>Sets the terminal
 492                                 device node to use if standard input,
 493                                 output or stderr are connected to a
 494                                 TTY (see above). Defaults to
 495                                 <filename>/dev/console</filename>.</para></listitem>
 496                         </varlistentry>
 497                         <varlistentry>
 498                                 <term><varname>TTYReset=</varname></term>
 499                                 <listitem><para>Reset the terminal
 500                                 device specified with
 501                                 <varname>TTYPath=</varname> before and
 502                                 after execution. Defaults to
 503                                 <literal>no</literal>.</para></listitem>
 504                         </varlistentry>
 505                         <varlistentry>
 506                                 <term><varname>TTYVHangup=</varname></term>
 507                                 <listitem><para>Disconnect all clients
 508                                 which have opened the terminal device
 509                                 specified with
 510                                 <varname>TTYPath=</varname>
 511                                 before and after execution. Defaults
 512                                 to
 513                                 <literal>no</literal>.</para></listitem>
 514                         </varlistentry>
 515                         <varlistentry>
 516                                 <term><varname>TTYVTDisallocate=</varname></term>
 517                                 <listitem><para>If the terminal
 518                                 device specified with
 519                                 <varname>TTYPath=</varname> is a
 520                                 virtual console terminal, try to
 521                                 deallocate the TTY before and after
 522                                 execution. This ensures that the
 523                                 screen and scrollback buffer is
 524                                 cleared. Defaults to
 525                                 <literal>no</literal>.</para></listitem>
 526                         </varlistentry>
 527                         <varlistentry>
 528                                 <term><varname>SyslogIdentifier=</varname></term>
 529                                 <listitem><para>Sets the process name
 530                                 to prefix log lines sent to syslog or
 531                                 the kernel log buffer with. If not set,
 532                                 defaults to the process name of the
 533                                 executed process. This option is only
 534                                 useful when
 535                                 <varname>StandardOutput=</varname> or
 536                                 <varname>StandardError=</varname> are
 537                                 set to <option>syslog</option> or
 538                                 <option>kmsg</option>.</para></listitem>
 539                         </varlistentry>
 540                         <varlistentry>
 541                                 <term><varname>SyslogFacility=</varname></term>
 542                                 <listitem><para>Sets the syslog
 543                                 facility to use when logging to
 544                                 syslog. One of <option>kern</option>,
 545                                 <option>user</option>,
 546                                 <option>mail</option>,
 547                                 <option>daemon</option>,
 548                                 <option>auth</option>,
 549                                 <option>syslog</option>,
 550                                 <option>lpr</option>,
 551                                 <option>news</option>,
 552                                 <option>uucp</option>,
 553                                 <option>cron</option>,
 554                                 <option>authpriv</option>,
 555                                 <option>ftp</option>,
 556                                 <option>local0</option>,
 557                                 <option>local1</option>,
 558                                 <option>local2</option>,
 559                                 <option>local3</option>,
 560                                 <option>local4</option>,
 561                                 <option>local5</option>,
 562                                 <option>local6</option> or
 563                                 <option>local7</option>. See
 564                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 565                                 for details. This option is only
 566                                 useful when
 567                                 <varname>StandardOutput=</varname> or
 568                                 <varname>StandardError=</varname> are
 569                                 set to <option>syslog</option>.
 570                                 Defaults to
 571                                 <option>daemon</option>.</para></listitem>
 572                         </varlistentry>
 573                         <varlistentry>
 574                                 <term><varname>SyslogLevel=</varname></term>
 575                                 <listitem><para>Default syslog level
 576                                 to use when logging to syslog or the
 577                                 kernel log buffer. One of
 578                                 <option>emerg</option>,
 579                                 <option>alert</option>,
 580                                 <option>crit</option>,
 581                                 <option>err</option>,
 582                                 <option>warning</option>,
 583                                 <option>notice</option>,
 584                                 <option>info</option>,
 585                                 <option>debug</option>. See
 586                                 <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 587                                 for details. This option is only
 588                                 useful when
 589                                 <varname>StandardOutput=</varname> or
 590                                 <varname>StandardError=</varname> are
 591                                 set to <option>syslog</option> or
 592                                 <option>kmsg</option>. Note that
 593                                 individual lines output by the daemon
 594                                 might be prefixed with a different log
 595                                 level which can be used to override
 596                                 the default log level specified
 597                                 here. The interpretation of these
 598                                 prefixes may be disabled with
 599                                 <varname>SyslogLevelPrefix=</varname>,
 600                                 see below. For details see
 601                                 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 602
 603                                 Defaults to
 604                                 <option>info</option>.</para></listitem>
 605                         </varlistentry>
 606
 607                         <varlistentry>
 608                                 <term><varname>SyslogLevelPrefix=</varname></term>
 609                                 <listitem><para>Takes a boolean
 610                                 argument. If true and
 611                                 <varname>StandardOutput=</varname> or
 612                                 <varname>StandardError=</varname> are
 613                                 set to <option>syslog</option>,
 614                                 <option>kmsg</option> or
 615                                 <option>journal</option>, log lines
 616                                 written by the executed process that
 617                                 are prefixed with a log level will be
 618                                 passed on to syslog with this log
 619                                 level set but the prefix removed. If
 620                                 set to false, the interpretation of
 621                                 these prefixes is disabled and the
 622                                 logged lines are passed on as-is. For
 623                                 details about this prefixing see
 624                                 <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 625                                 Defaults to true.</para></listitem>
 626                         </varlistentry>
 627
 628                         <varlistentry>
 629                                 <term><varname>TimerSlackNSec=</varname></term>
 630                                 <listitem><para>Sets the timer slack
 631                                 in nanoseconds for the executed
 632                                 processes. The timer slack controls
 633                                 the accuracy of wake-ups triggered by
 634                                 timers. See
 635                                 <citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 636                                 for more information. Note that in
 637                                 contrast to most other time span
 638                                 definitions this parameter takes an
 639                                 integer value in nano-seconds if no
 640                                 unit is specified. The usual time
 641                                 units are understood
 642                                 too.</para></listitem>
 643                         </varlistentry>
 644
 645                         <varlistentry>
 646                                 <term><varname>LimitCPU=</varname></term>
 647                                 <term><varname>LimitFSIZE=</varname></term>
 648                                 <term><varname>LimitDATA=</varname></term>
 649                                 <term><varname>LimitSTACK=</varname></term>
 650                                 <term><varname>LimitCORE=</varname></term>
 651                                 <term><varname>LimitRSS=</varname></term>
 652                                 <term><varname>LimitNOFILE=</varname></term>
 653                                 <term><varname>LimitAS=</varname></term>
 654                                 <term><varname>LimitNPROC=</varname></term>
 655                                 <term><varname>LimitMEMLOCK=</varname></term>
 656                                 <term><varname>LimitLOCKS=</varname></term>
 657                                 <term><varname>LimitSIGPENDING=</varname></term>
 658                                 <term><varname>LimitMSGQUEUE=</varname></term>
 659                                 <term><varname>LimitNICE=</varname></term>
 660                                 <term><varname>LimitRTPRIO=</varname></term>
 661                                 <term><varname>LimitRTTIME=</varname></term>
 662                                 <listitem><para>These settings control
 663                                 various resource limits for executed
 664                                 processes. See
 665                                 <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 666                                 for details. Use the string
 667                                 <varname>infinity</varname> to
 668                                 configure no limit on a specific
 669                                 resource.</para></listitem>
 670                         </varlistentry>
 671
 672                         <varlistentry>
 673                                 <term><varname>PAMName=</varname></term>
 674                                 <listitem><para>Sets the PAM service
 675                                 name to set up a session as. If set,
 676                                 the executed process will be
 677                                 registered as a PAM session under the
 678                                 specified service name. This is only
 679                                 useful in conjunction with the
 680                                 <varname>User=</varname> setting. If
 681                                 not set, no PAM session will be opened
 682                                 for the executed processes. See
 683                                 <citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 684                                 for details.</para></listitem>
 685                         </varlistentry>
 686
 687                         <varlistentry>
 688                                 <term><varname>TCPWrapName=</varname></term>
 689                                 <listitem><para>If this is a
 690                                 socket-activated service, this sets the
 691                                 tcpwrap service name to check the
 692                                 permission for the current connection
 693                                 with. This is only useful in
 694                                 conjunction with socket-activated
 695                                 services, and stream sockets (TCP) in
 696                                 particular. It has no effect on other
 697                                 socket types (e.g. datagram/UDP) and
 698                                 on processes unrelated to socket-based
 699                                 activation. If the tcpwrap
 700                                 verification fails, daemon start-up
 701                                 will fail and the connection is
 702                                 terminated. See
 703                                 <citerefentry><refentrytitle>tcpd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 704                                 for details. Note that this option may
 705                                 be used to do access control checks
 706                                 only. Shell commands and commands
 707                                 described in
 708                                 <citerefentry><refentrytitle>hosts_options</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 709                                 are not supported.</para></listitem>
 710                         </varlistentry>
 711
 712                         <varlistentry>
 713                                 <term><varname>CapabilityBoundingSet=</varname></term>
 714
 715                                 <listitem><para>Controls which
 716                                 capabilities to include in the
 717                                 capability bounding set for the
 718                                 executed process. See
 719                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 720                                 for details. Takes a whitespace-separated
 721                                 list of capability names as read by
 722                                 <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 723                                 e.g. <constant>CAP_SYS_ADMIN</constant>,
 724                                 <constant>CAP_DAC_OVERRIDE</constant>,
 725                                 <constant>CAP_SYS_PTRACE</constant>.
 726                                 Capabilities listed will be included
 727                                 in the bounding set, all others are
 728                                 removed. If the list of capabilities
 729                                 is prefixed with <literal>~</literal>,
 730                                 all but the listed capabilities will
 731                                 be included, the effect of the
 732                                 assignment inverted. Note that this
 733                                 option also affects the respective
 734                                 capabilities in the effective,
 735                                 permitted and inheritable capability
 736                                 sets, on top of what
 737                                 <varname>Capabilities=</varname>
 738                                 does. If this option is not used, the
 739                                 capability bounding set is not
 740                                 modified on process execution, hence
 741                                 no limits on the capabilities of the
 742                                 process are enforced. This option may
 743                                 appear more than once in which case
 744                                 the bounding sets are merged. If the
 745                                 empty string is assigned to this
 746                                 option, the bounding set is reset to
 747                                 the empty capability set, and all
 748                                 prior settings have no effect. If set
 749                                 to <literal>~</literal> (without any
 750                                 further argument), the bounding set is
 751                                 reset to the full set of available
 752                                 capabilities, also undoing any
 753                                 previous settings.</para></listitem>
 754                         </varlistentry>
 755
 756                         <varlistentry>
 757                                 <term><varname>SecureBits=</varname></term>
 758                                 <listitem><para>Controls the secure
 759                                 bits set for the executed process. See
 760                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 761                                 for details. Takes a list of strings:
 762                                 <option>keep-caps</option>,
 763                                 <option>keep-caps-locked</option>,
 764                                 <option>no-setuid-fixup</option>,
 765                                 <option>no-setuid-fixup-locked</option>,
 766                                 <option>noroot</option> and/or
 767                                 <option>noroot-locked</option>. This
 768                                 option may appear more than once in
 769                                 which case the secure bits are
 770                                 ORed. If the empty string is assigned
 771                                 to this option, the bits are reset to
 772                                 0.</para></listitem>
 773                         </varlistentry>
 774
 775                         <varlistentry>
 776                                 <term><varname>Capabilities=</varname></term>
 777                                 <listitem><para>Controls the
 778                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 779                                 set for the executed process. Take a
 780                                 capability string describing the
 781                                 effective, permitted and inherited
 782                                 capability sets as documented in
 783                                 <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 784                                 Note that these capability sets are
 785                                 usually influenced by the capabilities
 786                                 attached to the executed file. Due to
 787                                 that
 788                                 <varname>CapabilityBoundingSet=</varname>
 789                                 is probably the much more useful
 790                                 setting.</para></listitem>
 791                         </varlistentry>
 792
 793                         <varlistentry>
 794                                 <term><varname>ReadWriteDirectories=</varname></term>
 795                                 <term><varname>ReadOnlyDirectories=</varname></term>
 796                                 <term><varname>InaccessibleDirectories=</varname></term>
 797
 798                                 <listitem><para>Sets up a new
 799                                 file system namespace for executed
 800                                 processes. These options may be used
 801                                 to limit access a process might have
 802                                 to the main file system
 803                                 hierarchy. Each setting takes a
 804                                 space-separated list of absolute
 805                                 directory paths. Directories listed in
 806                                 <varname>ReadWriteDirectories=</varname>
 807                                 are accessible from within the
 808                                 namespace with the same access rights
 809                                 as from outside. Directories listed in
 810                                 <varname>ReadOnlyDirectories=</varname>
 811                                 are accessible for reading only,
 812                                 writing will be refused even if the
 813                                 usual file access controls would
 814                                 permit this. Directories listed in
 815                                 <varname>InaccessibleDirectories=</varname>
 816                                 will be made inaccessible for
 817                                 processes inside the namespace. Note
 818                                 that restricting access with these
 819                                 options does not extend to submounts
 820                                 of a directory. You must list
 821                                 submounts separately in these settings
 822                                 to ensure the same limited
 823                                 access. These options may be specified
 824                                 more than once in which case all
 825                                 directories listed will have limited
 826                                 access from within the namespace. If
 827                                 the empty string is assigned to this
 828                                 option, the specific list is reset, and
 829                                 all prior assignments have no
 830                                 effect.</para>
 831                                 <para>Paths in
 832                                 <varname>ReadOnlyDirectories=</varname>
 833                                 and
 834                                 <varname>InaccessibleDirectories=</varname>
 835                                 may be prefixed with
 836                                 <literal>-</literal>, in which case
 837                                 they will be ignored when they do not
 838                                 exist.</para></listitem>
 839                         </varlistentry>
 840
 841                         <varlistentry>
 842                                 <term><varname>PrivateTmp=</varname></term>
 843
 844                                 <listitem><para>Takes a boolean
 845                                 argument. If true, sets up a new file
 846                                 system namespace for the executed
 847                                 processes and mounts private
 848                                 <filename>/tmp</filename> and
 849                                 <filename>/var/tmp</filename> directories
 850                                 inside it, that are not shared by
 851                                 processes outside of the
 852                                 namespace. This is useful to secure
 853                                 access to temporary files of the
 854                                 process, but makes sharing between
 855                                 processes via
 856                                 <filename>/tmp</filename> or
 857                                 <filename>/var/tmp</filename>
 858                                 impossible. All temporary data created
 859                                 by service will be removed after service
 860                                 is stopped. Defaults to
 861                                 false.</para></listitem>
 862                         </varlistentry>
 863
 864                         <varlistentry>
 865                                 <term><varname>PrivateNetwork=</varname></term>
 866
 867                                 <listitem><para>Takes a boolean
 868                                 argument. If true, sets up a new
 869                                 network namespace for the executed
 870                                 processes and configures only the
 871                                 loopback network device
 872                                 <literal>lo</literal> inside it. No
 873                                 other network devices will be
 874                                 available to the executed process.
 875                                 This is useful to securely turn off
 876                                 network access by the executed
 877                                 process. Defaults to
 878                                 false.</para></listitem>
 879                         </varlistentry>
 880
 881                         <varlistentry>
 882                                 <term><varname>MountFlags=</varname></term>
 883
 884                                 <listitem><para>Takes a mount
 885                                 propagation flag:
 886                                 <option>shared</option>,
 887                                 <option>slave</option> or
 888                                 <option>private</option>, which
 889                                 control whether the file system
 890                                 namespace set up for this unit's
 891                                 processes will receive or propagate
 892                                 new mounts. See
 893                                 <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 894                                 for details. Default to
 895                                 <option>shared</option>.</para></listitem>
 896                         </varlistentry>
 897
 898                         <varlistentry>
 899                                 <term><varname>UtmpIdentifier=</varname></term>
 900
 901                                 <listitem><para>Takes a four
 902                                 character identifier string for an
 903                                 utmp/wtmp entry for this service. This
 904                                 should only be set for services such
 905                                 as <command>getty</command>
 906                                 implementations where utmp/wtmp
 907                                 entries must be created and cleared
 908                                 before and after execution. If the
 909                                 configured string is longer than four
 910                                 characters, it is truncated and the
 911                                 terminal four characters are
 912                                 used. This setting interprets %I style
 913                                 string replacements. This setting is
 914                                 unset by default, i.e. no utmp/wtmp
 915                                 entries are created or cleaned up for
 916                                 this service.</para></listitem>
 917                         </varlistentry>
 918
 919                         <varlistentry>
 920                                 <term><varname>IgnoreSIGPIPE=</varname></term>
 921
 922                                 <listitem><para>Takes a boolean
 923                                 argument. If true, causes <constant>SIGPIPE</constant> to be
 924                                 ignored in the executed
 925                                 process. Defaults to true because
 926                                 <constant>SIGPIPE</constant> generally is useful only in
 927                                 shell pipelines.</para></listitem>
 928                         </varlistentry>
 929
 930                         <varlistentry>
 931                                 <term><varname>NoNewPrivileges=</varname></term>
 932
 933                                 <listitem><para>Takes a boolean
 934                                 argument. If true, ensures that the
 935                                 service process and all its children
 936                                 can never gain new privileges. This
 937                                 option is more powerful than the respective
 938                                 secure bits flags (see above), as it
 939                                 also prohibits UID changes of any
 940                                 kind. This is the simplest, most
 941                                 effective way to ensure that a process
 942                                 and its children can never elevate
 943                                 privileges again.</para></listitem>
 944                         </varlistentry>
 945
 946                         <varlistentry>
 947                                 <term><varname>SystemCallFilter=</varname></term>
 948
 949                                 <listitem><para>Takes a space-separated
 950                                 list of system call
 951                                 names. If this setting is used, all
 952                                 system calls executed by the unit
 953                                 process except for the listed ones
 954                                 will result in immediate process
 955                                 termination with the
 956                                 <constant>SIGSYS</constant> signal
 957                                 (whitelisting). If the first character
 958                                 of the list is <literal>~</literal>,
 959                                 the effect is inverted: only the
 960                                 listed system calls will result in
 961                                 immediate process termination
 962                                 (blacklisting). If this option is used,
 963                                 <varname>NoNewPrivileges=yes</varname>
 964                                 is implied. This feature makes use of
 965                                 the Secure Computing Mode 2 interfaces
 966                                 of the kernel ('seccomp filtering')
 967                                 and is useful for enforcing a minimal
 968                                 sandboxing environment. Note that the
 969                                 <function>execve</function>,
 970                                 <function>rt_sigreturn</function>,
 971                                 <function>sigreturn</function>,
 972                                 <function>exit_group</function>,
 973                                 <function>exit</function> system calls
 974                                 are implicitly whitelisted and do not
 975                                 need to be listed explicitly. This
 976                                 option may be specified more than once
 977                                 in which case the filter masks are
 978                                 merged. If the empty string is
 979                                 assigned, the filter is reset, all
 980                                 prior assignments will have no
 981                                 effect.</para></listitem>
 982                         </varlistentry>
 983
 984                 </variablelist>
 985         </refsect1>
 986
 987         <refsect1>
 988                 <title>Environment variables in spawned processes</title>
 989
 990                 <para>Processes started by the system are executed in
 991                 a clean environment in which select variables
 992                 listed below are set. System processes started by systemd
 993                 do not inherit variables from PID 1, but processes
 994                 started by user systemd instances inherit all
 995                 environment variables from the user systemd instance.
 996                 </para>
 997
 998                 <variablelist class='environment-variables'>
 999                         <varlistentry>
1000                                 <term><varname>$PATH</varname></term>
1001
1002                                 <listitem><para>Colon-separated list
1003                                 of directiories to use when launching
1004                                 executables. Systemd uses a fixed
1005                                 value of
1006                                 <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
1007                                 </para></listitem>
1008                         </varlistentry>
1009
1010                         <varlistentry>
1011                                 <term><varname>$LANG</varname></term>
1012
1013                                 <listitem><para>Locale. Can be set in
1014                                 <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
1015                                 or on the kernel command line (see
1016                                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
1017                                 and
1018                                 <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
1019                                 </para></listitem>
1020                         </varlistentry>
1021
1022                         <varlistentry>
1023                                 <term><varname>$USER</varname></term>
1024                                 <term><varname>$LOGNAME</varname></term>
1025                                 <term><varname>$HOME</varname></term>
1026                                 <term><varname>$SHELL</varname></term>
1027
1028                                 <listitem><para>User name (twice), home
1029                                 directory, and the login shell.
1030                                 Set for the units which
1031                                 have <varname>User=</varname> set,
1032                                 which includes user
1033                                 <command>systemd</command> instances.
1034                                 See
1035                                 <citerefentry><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1036                                 </para></listitem>
1037                         </varlistentry>
1038
1039                         <varlistentry>
1040                                 <term><varname>$XDG_RUNTIME_DIR</varname></term>
1041
1042                                 <listitem><para>The directory for volatile
1043                                 state. Set for the user <command>systemd</command>
1044                                 instance, and also in user sessions.
1045                                 See
1046                                 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
1047                                 </para></listitem>
1048                         </varlistentry>
1049
1050                         <varlistentry>
1051                                 <term><varname>$XDG_SESSION_ID</varname></term>
1052                                 <term><varname>$XDG_SEAT</varname></term>
1053                                 <term><varname>$XDG_VTNR</varname></term>
1054
1055                                 <listitem><para>The identifier of the
1056                                 session, and the seat name, and
1057                                 virtual terminal of the session. Set
1058                                 by
1059                                 <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1060                                 for login sessions.
1061                                 <varname>$XDG_SEAT</varname> and
1062                                 <varname>$XDG_VTNR</varname> will be
1063                                 only set when attached to a seat and a
1064                                 tty.</para></listitem>
1065                         </varlistentry>
1066
1067                         <varlistentry>
1068                                 <term><varname>$MANAGERPID</varname></term>
1069
1070                                 <listitem><para>The PID of the user
1071                                 <command>systemd</command> instance,
1072                                 set for processes spawned by it.
1073                                 </para></listitem>
1074                         </varlistentry>
1075
1076                         <varlistentry>
1077                                 <term><varname>$LISTEN_FDS</varname></term>
1078                                 <term><varname>$LISTEN_PID</varname></term>
1079
1080                                 <listitem><para>Information about file
1081                                 descriptors passed to a service for
1082                                 socket activation.  See
1083                                 <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
1084                                 </para></listitem>
1085                         </varlistentry>
1086
1087                         <varlistentry>
1088                                 <term><varname>$TERM</varname></term>
1089
1090                                 <listitem><para>Terminal type, set
1091                                 only for units connected to a terminal
1092                                 (<varname>StandardInput=tty</varname>,
1093                                 <varname>StandardOutput=tty</varname>,
1094                                 or
1095                                 <varname>StandardError=tty</varname>).
1096                                 See
1097                                 <citerefentry><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
1098                                 </para></listitem>
1099                         </varlistentry>
1100                 </variablelist>
1101
1102                 <para>Additional variables may be configured by the
1103                 following means: for processes spawned in specific
1104                 units, use the <varname>Environment=</varname> and
1105                 <varname>EnvironmentFile=</varname> options above; to
1106                 specify variables globally, use
1107                 <varname>DefaultEnvironment=</varname> (see
1108                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
1109                 or the kernel option
1110                 <varname>systemd.setenv=</varname> (see
1111                 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Additional
1112                 variables may also be set through PAM,
1113                 c.f. <citerefentry><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
1114         </refsect1>
1115
1116         <refsect1>
1117                   <title>See Also</title>
1118                   <para>
1119                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1120                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1121                           <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1122                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1123                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1124                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1125                           <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1126                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1127                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1128                           <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1129                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1130                           <citerefentry><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
1131                   </para>
1132         </refsect1>
1133
1134 </refentry>