man/systemd.exec.xml

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