man/systemd.exec.xml

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   7   This file is part of systemd.
   8
   9   Copyright 2010 Lennart Poettering
  10
  11   systemd is free software; you can redistribute it and/or modify it
  12   under the terms of the GNU Lesser General Public License as published by
  13   the Free Software Foundation; either version 2.1 of the License, or
  14   (at your option) any later version.
  15
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  18   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  19   Lesser General Public License for more details.
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  24
  25 <refentry id="systemd.exec">
  26         <refentryinfo>
  27                 <title>systemd.exec</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>systemd.exec</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.exec</refname>
  47                 <refpurpose>Execution environment configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename><replaceable>service</replaceable>.service</filename>,
  52                 <filename><replaceable>socket</replaceable>.socket</filename>,
  53                 <filename><replaceable>mount</replaceable>.mount</filename>,
  54                 <filename><replaceable>swap</replaceable>.swap</filename></para>
  55         </refsynopsisdiv>
  56
  57         <refsect1>
  58                 <title>Description</title>
  59
  60                 <para>Unit configuration files for services, sockets,
  61                 mount points and swap devices share a subset of
  62                 configuration options which define the execution
  63                 environment of spawned processes.</para>
  64
  65                 <para>This man page lists the configuration options
  66                 shared by these four unit types. See
  67                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  68                 for the common options of all unit configuration
  69                 files, and
  70                 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  71                 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  72                 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  73                 and
  74                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  75                 for more information on the specific unit
  76                 configuration files. The execution specific
  77                 configuration options are configured in the [Service],
  78                 [Socket], [Mount], or [Swap] sections, depending on the unit
  79                 type.</para>
  80         </refsect1>
  81
  82         <refsect1>
  83                 <title>Options</title>
  84
  85                 <variablelist class='unit-directives'>
  86
  87                         <varlistentry>
  88                                 <term><varname>WorkingDirectory=</varname></term>
  89
  90                                 <listitem><para>Takes an absolute
  91                                 directory path. Sets the working
  92                                 directory for executed processes. If
  93                                 not set defaults to the root directory
  94                                 when systemd is running as a system
  95                                 instance and the respective user's
  96                                 home directory if run as
  97                                 user.</para></listitem>
  98                         </varlistentry>
  99
 100                         <varlistentry>
 101                                 <term><varname>RootDirectory=</varname></term>
 102
 103                                 <listitem><para>Takes an absolute
 104                                 directory path. Sets the root
 105                                 directory for executed processes, with
 106                                 the
 107                                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 108                                 system call. If this is used it must
 109                                 be ensured that the process and all
 110                                 its auxiliary files are available in
 111                                 the <function>chroot()</function>
 112                                 jail.</para></listitem>
 113                         </varlistentry>
 114
 115                         <varlistentry>
 116                                 <term><varname>User=</varname></term>
 117                                 <term><varname>Group=</varname></term>
 118
 119                                 <listitem><para>Sets the Unix user
 120                                 or group that the processes are executed
 121                                 as, respectively. Takes a single user or group
 122                                 name or ID as argument. If no group is
 123                                 set, the default group of the user is
 124                                 chosen.</para></listitem>
 125                         </varlistentry>
 126
 127                         <varlistentry>
 128                                 <term><varname>SupplementaryGroups=</varname></term>
 129
 130                                 <listitem><para>Sets the supplementary
 131                                 Unix groups the processes are executed
 132                                 as. This takes a space separated list
 133                                 of group names or IDs. This option may
 134                                 be specified more than once in which
 135                                 case all listed groups are set as
 136                                 supplementary groups. When the empty
 137                                 string is assigned the list of
 138                                 supplementary groups is reset, and all
 139                                 assignments prior to this one will
 140                                 have no effect. In any way, this
 141                                 option does not override, but extends
 142                                 the list of supplementary groups
 143                                 configured in the system group
 144                                 database for the
 145                                 user.</para></listitem>
 146                         </varlistentry>
 147
 148                         <varlistentry>
 149                                 <term><varname>Nice=</varname></term>
 150
 151                                 <listitem><para>Sets the default nice
 152                                 level (scheduling priority) for
 153                                 executed processes. Takes an integer
 154                                 between -20 (highest priority) and 19
 155                                 (lowest priority). See
 156                                 <citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 157                                 for details.</para></listitem>
 158                         </varlistentry>
 159
 160                         <varlistentry>
 161                                 <term><varname>OOMScoreAdjust=</varname></term>
 162
 163                                 <listitem><para>Sets the adjustment
 164                                 level for the Out-Of-Memory killer for
 165                                 executed processes. Takes an integer
 166                                 between -1000 (to disable OOM killing
 167                                 for this process) and 1000 (to make
 168                                 killing of this process under memory
 169                                 pressure very likely). See <ulink
 170                                 url="http://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
 171                                 for details.</para></listitem>
 172                         </varlistentry>
 173
 174                         <varlistentry>
 175                                 <term><varname>IOSchedulingClass=</varname></term>
 176
 177                                 <listitem><para>Sets the IO scheduling
 178                                 class for executed processes. Takes an
 179                                 integer between 0 and 3 or one of the
 180                                 strings <option>none</option>,
 181                                 <option>realtime</option>,
 182                                 <option>best-effort</option> or
 183                                 <option>idle</option>. See
 184                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 185                                 for details.</para></listitem>
 186                         </varlistentry>
 187
 188                         <varlistentry>
 189                                 <term><varname>IOSchedulingPriority=</varname></term>
 190
 191                                 <listitem><para>Sets the IO scheduling
 192                                 priority for executed processes. Takes
 193                                 an integer between 0 (highest
 194                                 priority) and 7 (lowest priority). The
 195                                 available priorities depend on the
 196                                 selected IO scheduling class (see
 197                                 above). See
 198                                 <citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 199                                 for details.</para></listitem>
 200                         </varlistentry>
 201
 202                         <varlistentry>
 203                                 <term><varname>CPUSchedulingPolicy=</varname></term>
 204
 205                                 <listitem><para>Sets the CPU
 206                                 scheduling policy for executed
 207                                 processes. Takes one of
 208                                 <option>other</option>,
 209                                 <option>batch</option>,
 210                                 <option>idle</option>,
 211                                 <option>fifo</option> or
 212                                 <option>rr</option>. See
 213                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 214                                 for details.</para></listitem>
 215                         </varlistentry>
 216
 217                         <varlistentry>
 218                                 <term><varname>CPUSchedulingPriority=</varname></term>
 219
 220                                 <listitem><para>Sets the CPU
 221                                 scheduling priority for executed
 222                                 processes. The available priority
 223                                 range depends on the selected CPU
 224                                 scheduling policy (see above). For
 225                                 real-time scheduling policies an
 226                                 integer between 1 (lowest priority)
 227                                 and 99 (highest priority) can be used.
 228                                 See <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 229                                 for details.
 230                                 </para></listitem>
 231                         </varlistentry>
 232
 233                         <varlistentry>
 234                                 <term><varname>CPUSchedulingResetOnFork=</varname></term>
 235
 236                                 <listitem><para>Takes a boolean
 237                                 argument. If true elevated CPU
 238                                 scheduling priorities and policies
 239                                 will be reset when the executed
 240                                 processes fork, and can hence not leak
 241                                 into child processes. See
 242                                 <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 243                                 for details. Defaults to false.</para></listitem>
 244                         </varlistentry>
 245
 246                         <varlistentry>
 247                                 <term><varname>CPUAffinity=</varname></term>
 248
 249                                 <listitem><para>Controls the CPU
 250                                 affinity of the executed
 251                                 processes. Takes a space-separated
 252                                 list of CPU indexes. This option may
 253                                 be specified more than once in which
 254                                 case the specificed CPU affinity masks
 255                                 are merged. If the empty string is
 256                                 assigned the mask is reset, all
 257                                 assignments prior to this will have no
 258                                 effect. See
 259                                 <citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 260                                 for details.</para></listitem>
 261                         </varlistentry>
 262
 263                         <varlistentry>
 264                                 <term><varname>UMask=</varname></term>
 265
 266                                 <listitem><para>Controls the file mode
 267                                 creation mask. Takes an access mode in
 268                                 octal notation. See
 269                                 <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 270                                 for details. Defaults to
 271                                 0022.</para></listitem>
 272                         </varlistentry>
 273
 274                         <varlistentry>
 275                                 <term><varname>Environment=</varname></term>
 276
 277                                 <listitem><para>Sets environment
 278                                 variables for executed
 279                                 processes. Takes a space-separated
 280                                 list of variable assignments. This
 281                                 option may be specified more than once
 282                                 in which case all listed variables
 283                                 will be set. If the same variable is
 284                                 set twice the later setting will
 285                                 override the earlier setting. If the
 286                                 empty string is assigned to this
 287                                 option the list of environment
 288                                 variables is reset, all prior
 289                                 assignments have no effect.
 290                                 Variable expansion is not performed
 291                                 inside the strings, however, specifier
 292                                 expansion is possible. $ character has
 293                                 no special meaning.
 294                                 If you need to assign a value containing spaces
 295                                 to a variable, use double quotes (")
 296                                 for the assignment.</para>
 297
 298                                 <para>Example:
 299                                 <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=word 5 6"</programlisting>
 300                                 gives three variables <literal>VAR1</literal>,
 301                                 <literal>VAR2</literal>, <literal>VAR3</literal>.
 302                                 </para>
 303
 304                                 <para>
 305                                 See
 306                                 <citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 307                                 for details about environment variables.</para></listitem>
 308                         </varlistentry>
 309                         <varlistentry>
 310                                 <term><varname>EnvironmentFile=</varname></term>
 311                                 <listitem><para>Similar to
 312                                 <varname>Environment=</varname> but
 313                                 reads the environment variables from a
 314                                 text file. The text file should
 315                                 contain new-line separated variable
 316                                 assignments. Empty lines and lines
 317                                 starting with ; or # will be ignored,
 318                                 which may be used for commenting. A line
 319                                 ending with a backslash will be concatenated
 320                                 with the following one, allowing multiline variable
 321                                 definitions. The parser strips leading
 322                                 and trailing whitespace from the values
 323                                 of assignments, unless you use
 324                                 double quotes (").</para>
 325
 326                                 <para>The argument passed should be an
 327                                 absolute file name or wildcard
 328                                 expression, optionally prefixed with
 329                                 "-", which indicates that if the file
 330                                 does not exist it won't be read and no
 331                                 error or warning message is logged.
 332                                 This option may be specified more than
 333                                 once in which case all specified files
 334                                 are read. If the empty string is
 335                                 assigned to this option the list of
 336                                 file to read is reset, all prior
 337                                 assignments have no 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
 721                                 separated list of capability names as
 722                                 read by
 723                                 <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 724                                 e.g. <constant>CAP_SYS_ADMIN</constant>,
 725                                 <constant>CAP_DAC_OVERRIDE</constant>,
 726                                 <constant>CAP_SYS_PTRACE</constant>.
 727                                 Capabilities listed will be included
 728                                 in the bounding set, all others are
 729                                 removed. If the list of capabilities
 730                                 is prefixed with <literal>~</literal>
 731                                 all but the listed capabilities will
 732                                 be included, the effect of the
 733                                 assignment inverted. Note that this
 734                                 option also affects the respective
 735                                 capabilities in the effective,
 736                                 permitted and inheritable capability
 737                                 sets, on top of what
 738                                 <varname>Capabilities=</varname>
 739                                 does. If this option is not used the
 740                                 capability bounding set is not
 741                                 modified on process execution, hence
 742                                 no limits on the capabilities of the
 743                                 process are enforced. This option may
 744                                 appear more than once in which case
 745                                 the bounding sets are merged. If the
 746                                 empty string is assigned to this
 747                                 option the bounding set is reset to
 748                                 the empty capability set, and all
 749                                 prior settings have no effect. If set
 750                                 to <literal>~</literal> (without any
 751                                 further argument) the bounding set is
 752                                 reset to the full set of available
 753                                 capabilities, also undoing any
 754                                 previous settings.</para></listitem>
 755                         </varlistentry>
 756
 757                         <varlistentry>
 758                                 <term><varname>SecureBits=</varname></term>
 759                                 <listitem><para>Controls the secure
 760                                 bits set for the executed process. See
 761                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 762                                 for details. Takes a list of strings:
 763                                 <option>keep-caps</option>,
 764                                 <option>keep-caps-locked</option>,
 765                                 <option>no-setuid-fixup</option>,
 766                                 <option>no-setuid-fixup-locked</option>,
 767                                 <option>noroot</option> and/or
 768                                 <option>noroot-locked</option>. This
 769                                 option may appear more than once in
 770                                 which case the secure bits are
 771                                 ORed. If the empty string is assigned
 772                                 to this option the bits are reset to
 773                                 0.</para></listitem>
 774                         </varlistentry>
 775
 776                         <varlistentry>
 777                                 <term><varname>Capabilities=</varname></term>
 778                                 <listitem><para>Controls the
 779                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 780                                 set for the executed process. Take a
 781                                 capability string describing the
 782                                 effective, permitted and inherited
 783                                 capability sets as documented in
 784                                 <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 785                                 Note that these capability sets are
 786                                 usually influenced by the capabilities
 787                                 attached to the executed file. Due to
 788                                 that
 789                                 <varname>CapabilityBoundingSet=</varname>
 790                                 is probably the much more useful
 791                                 setting.</para></listitem>
 792                         </varlistentry>
 793
 794                         <varlistentry>
 795                                 <term><varname>ControlGroup=</varname></term>
 796
 797                                 <listitem><para>Controls the control
 798                                 groups the executed processes shall be
 799                                 made members of. Takes a
 800                                 space-separated list of cgroup
 801                                 identifiers. A cgroup identifier is
 802                                 formatted like
 803                                 <filename noindex='true'>cpu:/foo/bar</filename>,
 804                                 where "cpu" indicates the kernel
 805                                 control group controller used, and
 806                                 <filename noindex='true'>/foo/bar</filename> is the
 807                                 control group path. The controller
 808                                 name and ":" may be omitted in which
 809                                 case the named systemd control group
 810                                 hierarchy is implied. Alternatively,
 811                                 the path and ":" may be omitted, in
 812                                 which case the default control group
 813                                 path for this unit is implied.</para>
 814
 815                                 <para>This option may be used to place
 816                                 executed processes in arbitrary groups
 817                                 in arbitrary hierarchies -- which may
 818                                 then be externally configured with
 819                                 additional execution limits. By
 820                                 default systemd will place all
 821                                 executed processes in separate
 822                                 per-unit control groups (named after
 823                                 the unit) in the systemd named
 824                                 hierarchy. This option is primarily
 825                                 intended to place executed processes
 826                                 in specific paths in specific kernel
 827                                 controller hierarchies. It is not
 828                                 recommended to manipulate the service
 829                                 control group path in the private
 830                                 systemd named hierarchy
 831                                 (i.e. <literal>name=systemd</literal>),
 832                                 and doing this might result in
 833                                 undefined behaviour. For details about
 834                                 control groups see <ulink
 835                                 url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para>
 836
 837                                 <para>This option may appear more than
 838                                 once, in which case the list of
 839                                 control group assignments is
 840                                 merged. If the same hierarchy gets two
 841                                 different paths assigned only the
 842                                 later setting will take effect. If the
 843                                 empty string is assigned to this
 844                                 option the list of control group
 845                                 assignments is reset, all previous
 846                                 assignments will have no
 847                                 effect.</para>
 848
 849                                 <para>Note that the list of control
 850                                 group assignments of a unit is
 851                                 extended implicitly based on the
 852                                 settings of
 853                                 <varname>DefaultControllers=</varname>
 854                                 of
 855                                 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 856                                 but a unit's
 857                                 <varname>ControlGroup=</varname>
 858                                 setting for a specific controller
 859                                 takes precedence.</para></listitem>
 860                         </varlistentry>
 861
 862                         <varlistentry>
 863                                 <term><varname>ControlGroupModify=</varname></term>
 864                                 <listitem><para>Takes a boolean
 865                                 argument. If true, the control groups
 866                                 created for this unit will be owned by
 867                                 the user specified with
 868                                 <varname>User=</varname> (and the
 869                                 appropriate group), and he/she can create
 870                                 subgroups as well as add processes to
 871                                 the group.</para></listitem>
 872                         </varlistentry>
 873
 874                         <varlistentry>
 875                                 <term><varname>ControlGroupPersistent=</varname></term>
 876                                 <listitem><para>Takes a boolean
 877                                 argument. If true, the control groups
 878                                 created for this unit will be marked
 879                                 to be persistent, i.e. systemd will
 880                                 not remove them when stopping the
 881                                 unit. The default is false, meaning
 882                                 that the control groups will be
 883                                 removed when the unit is stopped. For
 884                                 details about the semantics of this
 885                                 logic see <ulink
 886                                 url="http://www.freedesktop.org/wiki/Software/systemd/PaxControlGroups">PaxControlGroups</ulink>.</para></listitem>
 887                         </varlistentry>
 888
 889                         <varlistentry>
 890                                 <term><varname>ControlGroupAttribute=</varname></term>
 891
 892                                 <listitem><para>Set a specific control
 893                                 group attribute for executed
 894                                 processes, and (if needed) add the
 895                                 executed processes to a cgroup in the
 896                                 hierarchy of the controller the
 897                                 attribute belongs to. Takes two
 898                                 space-separated arguments: the
 899                                 attribute name (syntax is
 900                                 <literal>cpu.shares</literal> where
 901                                 <literal>cpu</literal> refers to a
 902                                 specific controller and
 903                                 <literal>shares</literal> to the
 904                                 attribute name), and the attribute
 905                                 value. Example:
 906                                 <literal>ControlGroupAttribute=cpu.shares
 907                                 512</literal>. If this option is used
 908                                 for an attribute that belongs to a
 909                                 kernel controller hierarchy the unit
 910                                 is not already configured to be added
 911                                 to (for example via the
 912                                 <literal>ControlGroup=</literal>
 913                                 option) then the unit will be added to
 914                                 the controller and the default unit
 915                                 cgroup path is implied. Thus, using
 916                                 <varname>ControlGroupAttribute=</varname>
 917                                 is in most cases sufficient to make
 918                                 use of control group enforcements,
 919                                 explicit
 920                                 <varname>ControlGroup=</varname> are
 921                                 only necessary in case the implied
 922                                 default control group path for a
 923                                 service is not desirable. For details
 924                                 about control group attributes see
 925                                 <ulink
 926                                 url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>. This
 927                                 option may appear more than once, in
 928                                 order to set multiple control group
 929                                 attributes. If this option is used
 930                                 multiple times for the same cgroup
 931                                 attribute only the later setting takes
 932                                 effect. If the empty string is
 933                                 assigned to this option the list of
 934                                 attributes is reset, all previous
 935                                 cgroup attribute settings have no
 936                                 effect, including those done with
 937                                 <varname>CPUShares=</varname>,
 938                                 <varname>MemoryLimit=</varname>,
 939                                 <varname>MemorySoftLimit</varname>,
 940                                 <varname>DeviceAllow=</varname>,
 941                                 <varname>DeviceDeny=</varname>,
 942                                 <varname>BlockIOWeight=</varname>,
 943                                 <varname>BlockIOReadBandwidth=</varname>,
 944                                 <varname>BlockIOWriteBandwidth=</varname>.
 945                                 </para></listitem>
 946                         </varlistentry>
 947
 948                         <varlistentry>
 949                                 <term><varname>CPUShares=</varname></term>
 950
 951                                 <listitem><para>Assign the specified
 952                                 overall CPU time shares to the
 953                                 processes executed. Takes an integer
 954                                 value. This controls the
 955                                 <literal>cpu.shares</literal> control
 956                                 group attribute, which defaults to
 957                                 1024. For details about this control
 958                                 group attribute see <ulink
 959                                 url="http://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt">sched-design-CFS.txt</ulink>.</para></listitem>
 960                         </varlistentry>
 961
 962                         <varlistentry>
 963                                 <term><varname>MemoryLimit=</varname></term>
 964                                 <term><varname>MemorySoftLimit=</varname></term>
 965
 966                                 <listitem><para>Limit the overall memory usage
 967                                 of the executed processes to a certain
 968                                 size. Takes a memory size in bytes. If
 969                                 the value is suffixed with K, M, G or
 970                                 T the specified memory size is parsed
 971                                 as Kilobytes, Megabytes, Gigabytes,
 972                                 or Terabytes (to the base
 973                                 1024), respectively. This controls the
 974                                 <literal>memory.limit_in_bytes</literal>
 975                                 and
 976                                 <literal>memory.soft_limit_in_bytes</literal>
 977                                 control group attributes. For details
 978                                 about these control group attributes
 979                                 see <ulink
 980                                 url="http://www.kernel.org/doc/Documentation/cgroups/memory.txt">memory.txt</ulink>.</para></listitem>
 981                         </varlistentry>
 982
 983                         <varlistentry>
 984                                 <term><varname>DeviceAllow=</varname></term>
 985                                 <term><varname>DeviceDeny=</varname></term>
 986
 987                                 <listitem><para>Control access to
 988                                 specific device nodes by the executed processes. Takes two
 989                                 space separated strings: a device node
 990                                 path (such as
 991                                 <filename>/dev/null</filename>)
 992                                 followed by a combination of r, w, m
 993                                 to control reading, writing, or
 994                                 creating of the specific device node
 995                                 by the unit, respectively. This controls the
 996                                 <literal>devices.allow</literal>
 997                                 and
 998                                 <literal>devices.deny</literal>
 999                                 control group attributes. For details
1000                                 about these control group attributes
1001                                 see <ulink
1002                                 url="http://www.kernel.org/doc/Documentation/cgroups/devices.txt">devices.txt</ulink>.</para></listitem>
1003                         </varlistentry>
1004
1005                         <varlistentry>
1006                                 <term><varname>BlockIOWeight=</varname></term>
1007
1008                                 <listitem><para>Set the default or
1009                                 per-device overall block IO weight
1010                                 value for the executed
1011                                 processes. Takes either a single
1012                                 weight value (between 10 and 1000) to
1013                                 set the default block IO weight, or a
1014                                 space separated pair of a file path
1015                                 and a weight value to specify the
1016                                 device specific weight value (Example:
1017                                 "/dev/sda 500"). The file path may be
1018                                 specified as path to a block device
1019                                 node or as any other file in which
1020                                 case the backing block device of the
1021                                 file system of the file is
1022                                 determined. This controls the
1023                                 <literal>blkio.weight</literal> and
1024                                 <literal>blkio.weight_device</literal>
1025                                 control group attributes, which
1026                                 default to 1000. Use this option
1027                                 multiple times to set weights for
1028                                 multiple devices. For details about
1029                                 these control group attributes see
1030                                 <ulink
1031                                 url="http://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.</para></listitem>
1032                         </varlistentry>
1033
1034                         <varlistentry>
1035                                 <term><varname>BlockIOReadBandwidth=</varname></term>
1036                                 <term><varname>BlockIOWriteBandwidth=</varname></term>
1037
1038                                 <listitem><para>Set the per-device
1039                                 overall block IO bandwidth limit for
1040                                 the executed processes. Takes a space
1041                                 separated pair of a file path and a
1042                                 bandwidth value (in bytes per second)
1043                                 to specify the device specific
1044                                 bandwidth. The file path may be
1045                                 specified as path to a block device
1046                                 node or as any other file in which
1047                                 case the backing block device of the
1048                                 file system of the file is determined.
1049                                 If the bandwidth is suffixed with K, M,
1050                                 G, or T the specified bandwidth is
1051                                 parsed as Kilobytes, Megabytes,
1052                                 Gigabytes, or Terabytes, respectively (Example:
1053                                 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0
1054                                 5M"). This controls the
1055                                 <literal>blkio.read_bps_device</literal>
1056                                 and
1057                                 <literal>blkio.write_bps_device</literal>
1058                                 control group attributes. Use this
1059                                 option multiple times to set bandwidth
1060                                 limits for multiple devices. For
1061                                 details about these control group
1062                                 attributes see <ulink
1063                                 url="http://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt">blkio-controller.txt</ulink>.</para></listitem>
1064                         </varlistentry>
1065
1066                         <varlistentry>
1067                                 <term><varname>ReadWriteDirectories=</varname></term>
1068                                 <term><varname>ReadOnlyDirectories=</varname></term>
1069                                 <term><varname>InaccessibleDirectories=</varname></term>
1070
1071                                 <listitem><para>Sets up a new
1072                                 file system namespace for executed
1073                                 processes. These options may be used
1074                                 to limit access a process might have
1075                                 to the main file system
1076                                 hierarchy. Each setting takes a
1077                                 space-separated list of absolute
1078                                 directory paths. Directories listed in
1079                                 <varname>ReadWriteDirectories=</varname>
1080                                 are accessible from within the
1081                                 namespace with the same access rights
1082                                 as from outside. Directories listed in
1083                                 <varname>ReadOnlyDirectories=</varname>
1084                                 are accessible for reading only,
1085                                 writing will be refused even if the
1086                                 usual file access controls would
1087                                 permit this. Directories listed in
1088                                 <varname>InaccessibleDirectories=</varname>
1089                                 will be made inaccessible for
1090                                 processes inside the namespace. Note
1091                                 that restricting access with these
1092                                 options does not extend to submounts
1093                                 of a directory. You must list
1094                                 submounts separately in these settings
1095                                 to ensure the same limited
1096                                 access. These options may be specified
1097                                 more than once in which case all
1098                                 directories listed will have limited
1099                                 access from within the namespace. If
1100                                 the empty string is assigned to this
1101                                 option the specific list is reset, and
1102                                 all prior assignments have no
1103                                 effect.</para></listitem>
1104                         </varlistentry>
1105
1106                         <varlistentry>
1107                                 <term><varname>PrivateTmp=</varname></term>
1108
1109                                 <listitem><para>Takes a boolean
1110                                 argument. If true sets up a new file
1111                                 system namespace for the executed
1112                                 processes and mounts private
1113                                 <filename>/tmp</filename> and
1114                                 <filename>/var/tmp</filename> directories
1115                                 inside it, that are not shared by
1116                                 processes outside of the
1117                                 namespace. This is useful to secure
1118                                 access to temporary files of the
1119                                 process, but makes sharing between
1120                                 processes via
1121                                 <filename>/tmp</filename> or
1122                                 <filename>/var/tmp</filename>
1123                                 impossible. All temporary data created
1124                                 by service will be removed after service
1125                                 is stopped. Defaults to
1126                                 false.</para></listitem>
1127                         </varlistentry>
1128
1129                         <varlistentry>
1130                                 <term><varname>PrivateNetwork=</varname></term>
1131
1132                                 <listitem><para>Takes a boolean
1133                                 argument. If true sets up a new
1134                                 network namespace for the executed
1135                                 processes and configures only the
1136                                 loopback network device
1137                                 <literal>lo</literal> inside it. No
1138                                 other network devices will be
1139                                 available to the executed process.
1140                                 This is useful to securely turn off
1141                                 network access by the executed
1142                                 process. Defaults to
1143                                 false.</para></listitem>
1144                         </varlistentry>
1145
1146                         <varlistentry>
1147                                 <term><varname>MountFlags=</varname></term>
1148
1149                                 <listitem><para>Takes a mount
1150                                 propagation flag:
1151                                 <option>shared</option>,
1152                                 <option>slave</option> or
1153                                 <option>private</option>, which
1154                                 control whether the file system
1155                                 namespace set up for this unit's
1156                                 processes will receive or propagate
1157                                 new mounts. See
1158                                 <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
1159                                 for details. Default to
1160                                 <option>shared</option>.</para></listitem>
1161                         </varlistentry>
1162
1163                         <varlistentry>
1164                                 <term><varname>UtmpIdentifier=</varname></term>
1165
1166                                 <listitem><para>Takes a four
1167                                 character identifier string for an
1168                                 utmp/wtmp entry for this service. This
1169                                 should only be set for services such
1170                                 as <command>getty</command>
1171                                 implementations where utmp/wtmp
1172                                 entries must be created and cleared
1173                                 before and after execution. If the
1174                                 configured string is longer than four
1175                                 characters it is truncated and the
1176                                 terminal four characters are
1177                                 used. This setting interprets %I style
1178                                 string replacements. This setting is
1179                                 unset by default, i.e. no utmp/wtmp
1180                                 entries are created or cleaned up for
1181                                 this service.</para></listitem>
1182                         </varlistentry>
1183
1184                         <varlistentry>
1185                                 <term><varname>IgnoreSIGPIPE=</varname></term>
1186
1187                                 <listitem><para>Takes a boolean
1188                                 argument. If true causes SIGPIPE to be
1189                                 ignored in the executed
1190                                 process. Defaults to true, since
1191                                 SIGPIPE generally is useful only in
1192                                 shell pipelines.</para></listitem>
1193                         </varlistentry>
1194
1195                         <varlistentry>
1196                                 <term><varname>NoNewPrivileges=</varname></term>
1197
1198                                 <listitem><para>Takes a boolean
1199                                 argument. If true ensures that the
1200                                 service process and all its children
1201                                 can never gain new privileges. This
1202                                 option is more powerful than the respective
1203                                 secure bits flags (see above), as it
1204                                 also prohibits UID changes of any
1205                                 kind. This is the simplest, most
1206                                 effective way to ensure that a process
1207                                 and its children can never elevate
1208                                 privileges again.</para></listitem>
1209                         </varlistentry>
1210
1211                         <varlistentry>
1212                                 <term><varname>SystemCallFilter=</varname></term>
1213
1214                                 <listitem><para>Takes a space
1215                                 separated list of system call
1216                                 names. If this setting is used all
1217                                 system calls executed by the unit
1218                                 process except for the listed ones
1219                                 will result in immediate process
1220                                 termination with the
1221                                 <constant>SIGSYS</constant> signal
1222                                 (whitelisting). If the first character
1223                                 of the list is <literal>~</literal>
1224                                 the effect is inverted: only the
1225                                 listed system calls will result in
1226                                 immediate process termination
1227                                 (blacklisting). If this option is used
1228                                 <varname>NoNewPrivileges=yes</varname>
1229                                 is implied. This feature makes use of
1230                                 the Secure Computing Mode 2 interfaces
1231                                 of the kernel ('seccomp filtering')
1232                                 and is useful for enforcing a minimal
1233                                 sandboxing environment. Note that the
1234                                 <function>execve</function>,
1235                                 <function>rt_sigreturn</function>,
1236                                 <function>sigreturn</function>,
1237                                 <function>exit_group</function>,
1238                                 <function>exit</function> system calls
1239                                 are implicitly whitelisted and don't
1240                                 need to be listed explicitly. This
1241                                 option may be specified more than once
1242                                 in which case the filter masks are
1243                                 merged. If the empty string is
1244                                 assigned the filter is reset, all
1245                                 prior assignments will have no
1246                                 effect.</para></listitem>
1247                         </varlistentry>
1248
1249                 </variablelist>
1250         </refsect1>
1251
1252         <refsect1>
1253                   <title>See Also</title>
1254                   <para>
1255                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1256                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1257                           <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1258                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1259                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1260                           <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1261                           <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1262                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1263                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1264                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1265                   </para>
1266         </refsect1>
1267
1268 </refentry>