1<?xml version='1.0'?> 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> 4<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> 5 6<refentry id="systemd.resource-control" xmlns:xi="http://www.w3.org/2001/XInclude"> 7 <refentryinfo> 8 <title>systemd.resource-control</title> 9 <productname>systemd</productname> 10 </refentryinfo> 11 12 <refmeta> 13 <refentrytitle>systemd.resource-control</refentrytitle> 14 <manvolnum>5</manvolnum> 15 </refmeta> 16 17 <refnamediv> 18 <refname>systemd.resource-control</refname> 19 <refpurpose>Resource control unit settings</refpurpose> 20 </refnamediv> 21 22 <refsynopsisdiv> 23 <para> 24 <filename><replaceable>slice</replaceable>.slice</filename>, 25 <filename><replaceable>scope</replaceable>.scope</filename>, 26 <filename><replaceable>service</replaceable>.service</filename>, 27 <filename><replaceable>socket</replaceable>.socket</filename>, 28 <filename><replaceable>mount</replaceable>.mount</filename>, 29 <filename><replaceable>swap</replaceable>.swap</filename> 30 </para> 31 </refsynopsisdiv> 32 33 <refsect1> 34 <title>Description</title> 35 36 <para>Unit configuration files for services, slices, scopes, sockets, mount points, and swap devices share a subset 37 of configuration options for resource control of spawned processes. Internally, this relies on the Linux Control 38 Groups (cgroups) kernel concept for organizing processes in a hierarchical tree of named groups for the purpose of 39 resource management.</para> 40 41 <para>This man page lists the configuration options shared by 42 those six unit types. See 43 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> 44 for the common options of all unit configuration files, and 45 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 46 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 47 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 48 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 49 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 50 and 51 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry> 52 for more information on the specific unit configuration files. The 53 resource control configuration options are configured in the 54 [Slice], [Scope], [Service], [Socket], [Mount], or [Swap] 55 sections, depending on the unit type.</para> 56 57 <para>In addition, options which control resources available to programs 58 <emphasis>executed</emphasis> by systemd are listed in 59 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. 60 Those options complement options listed here.</para> 61 62 <para>See the <ulink 63 url="https://www.freedesktop.org/wiki/Software/systemd/ControlGroupInterface/">New 64 Control Group Interfaces</ulink> for an introduction on how to make 65 use of resource control APIs from programs.</para> 66 67 <refsect2> 68 <title>Setting resource controls for a group of related units</title> 69 70 <para>As described in 71 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, the 72 settings listed here may be set through the main file of a unit and drop-in snippets in 73 <filename index="false">*.d/</filename> directories. The list of directories searched for drop-ins 74 includes names formed by repeatedly truncating the unit name after all dashes. This is particularly 75 convenient to set resource limits for a group of units with similar names.</para> 76 77 <para>For example, every user gets their own slice 78 <filename>user-<replaceable>nnn</replaceable>.slice</filename>. Drop-ins with local configuration that 79 affect user 1000 may be placed in 80 <filename index="false">/etc/systemd/system/user-1000.slice</filename>, 81 <filename index="false">/etc/systemd/system/user-1000.slice.d/*.conf</filename>, but also 82 <filename index="false">/etc/systemd/system/user-.slice.d/*.conf</filename>. This last directory 83 applies to all user slices.</para> 84 </refsect2> 85 </refsect1> 86 87 <refsect1> 88 <title>Implicit Dependencies</title> 89 90 <para>The following dependencies are implicitly added:</para> 91 92 <itemizedlist> 93 <listitem><para>Units with the <varname>Slice=</varname> setting set automatically acquire 94 <varname>Requires=</varname> and <varname>After=</varname> dependencies on the specified 95 slice unit.</para></listitem> 96 </itemizedlist> 97 </refsect1> 98 99 <!-- We don't have any default dependency here. --> 100 101 <refsect1> 102 <title>Unified and Legacy Control Group Hierarchies</title> 103 104 <para>The unified control group hierarchy is the new version of kernel control group interface, see 105 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2</ulink>. 106 Depending on the resource type, there are differences in resource control capabilities. Also, because of 107 interface changes, some resource types have separate set of options on the unified hierarchy.</para> 108 109 <para> 110 <variablelist> 111 112 <varlistentry> 113 <term>CPU</term> 114 <listitem> 115 <para><varname>CPUWeight=</varname> and <varname>StartupCPUWeight=</varname> replace 116 <varname>CPUShares=</varname> and <varname>StartupCPUShares=</varname>, respectively.</para> 117 118 <para>The <literal>cpuacct</literal> controller does not exist separately on the unified hierarchy.</para> 119 </listitem> 120 </varlistentry> 121 122 <varlistentry> 123 <term>Memory</term> 124 <listitem> 125 <para><varname>MemoryMax=</varname> replaces <varname>MemoryLimit=</varname>. <varname>MemoryLow=</varname> 126 and <varname>MemoryHigh=</varname> are effective only on unified hierarchy.</para> 127 </listitem> 128 </varlistentry> 129 130 <varlistentry> 131 <term>IO</term> 132 <listitem> 133 <para><literal>IO</literal>-prefixed settings are a superset of and replace 134 <literal>BlockIO</literal>-prefixed ones. On unified hierarchy, IO resource control also applies 135 to buffered writes.</para> 136 </listitem> 137 </varlistentry> 138 139 </variablelist> 140 </para> 141 142 <para>To ease the transition, there is best-effort translation between the two versions of settings. For each 143 controller, if any of the settings for the unified hierarchy are present, all settings for the legacy hierarchy are 144 ignored. If the resulting settings are for the other type of hierarchy, the configurations are translated before 145 application.</para> 146 147 <para>Legacy control group hierarchy (see <ulink 148 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/">Control Groups version 1</ulink>), 149 also called cgroup-v1, doesn't allow safe delegation of controllers to unprivileged processes. If the 150 system uses the legacy control group hierarchy, resource control is disabled for the systemd user 151 instance, see 152 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para> 153 </refsect1> 154 155 <refsect1> 156 <title>Options</title> 157 158 <para>Units of the types listed above can have settings 159 for resource control configuration:</para> 160 161 <variablelist class='unit-directives'> 162 163 <varlistentry> 164 <term><varname>CPUAccounting=</varname></term> 165 166 <listitem> 167 <para>Turn on CPU usage accounting for this unit. Takes a 168 boolean argument. Note that turning on CPU accounting for 169 one unit will also implicitly turn it on for all units 170 contained in the same slice and for all its parent slices 171 and the units contained therein. The system default for this 172 setting may be controlled with 173 <varname>DefaultCPUAccounting=</varname> in 174 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 175 </listitem> 176 </varlistentry> 177 178 <varlistentry> 179 <term><varname>CPUWeight=<replaceable>weight</replaceable></varname></term> 180 <term><varname>StartupCPUWeight=<replaceable>weight</replaceable></varname></term> 181 182 <listitem> 183 <para>Assign the specified CPU time weight to the processes executed, if the unified control group 184 hierarchy is used on the system. These options take an integer value and control the 185 <literal>cpu.weight</literal> control group attribute. The allowed range is 1 to 10000. Defaults to 186 100. For details about this control group attribute, see <ulink 187 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2</ulink> 188 and <ulink url="https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS 189 Scheduler</ulink>. The available CPU time is split up among all units within one slice relative to 190 their CPU time weight. A higher weight means more CPU time, a lower weight means less.</para> 191 192 <para>While <varname>StartupCPUWeight=</varname> applies to the startup and shutdown phases of the system, 193 <varname>CPUWeight=</varname> applies to normal runtime of the system, and if the former is not set also to 194 the startup and shutdown phases. Using <varname>StartupCPUWeight=</varname> allows prioritizing specific services at 195 boot-up and shutdown differently than during normal runtime.</para> 196 197 <para>These settings replace <varname>CPUShares=</varname> and <varname>StartupCPUShares=</varname>.</para> 198 </listitem> 199 </varlistentry> 200 201 <varlistentry> 202 <term><varname>CPUQuota=</varname></term> 203 204 <listitem> 205 <para>Assign the specified CPU time quota to the processes executed. Takes a percentage value, suffixed with 206 "%". The percentage specifies how much CPU time the unit shall get at maximum, relative to the total CPU time 207 available on one CPU. Use values > 100% for allotting CPU time on more than one CPU. This controls the 208 <literal>cpu.max</literal> attribute on the unified control group hierarchy and 209 <literal>cpu.cfs_quota_us</literal> on legacy. For details about these control group attributes, see <ulink 210 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2</ulink> and <ulink 211 url="https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt">sched-bwc.txt</ulink>. 212 Setting <varname>CPUQuota=</varname> to an empty value unsets the quota.</para> 213 214 <para>Example: <varname>CPUQuota=20%</varname> ensures that the executed processes will never get more than 215 20% CPU time on one CPU.</para> 216 217 </listitem> 218 </varlistentry> 219 220 <varlistentry> 221 <term><varname>CPUQuotaPeriodSec=</varname></term> 222 223 <listitem> 224 <para>Assign the duration over which the CPU time quota specified by <varname>CPUQuota=</varname> is measured. 225 Takes a time duration value in seconds, with an optional suffix such as "ms" for milliseconds (or "s" for seconds.) 226 The default setting is 100ms. The period is clamped to the range supported by the kernel, which is [1ms, 1000ms]. 227 Additionally, the period is adjusted up so that the quota interval is also at least 1ms. 228 Setting <varname>CPUQuotaPeriodSec=</varname> to an empty value resets it to the default.</para> 229 230 <para>This controls the second field of <literal>cpu.max</literal> attribute on the unified control group hierarchy 231 and <literal>cpu.cfs_period_us</literal> on legacy. For details about these control group attributes, see 232 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2</ulink> and 233 <ulink url="https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS Scheduler</ulink>.</para> 234 235 <para>Example: <varname>CPUQuotaPeriodSec=10ms</varname> to request that the CPU quota is measured in periods of 10ms.</para> 236 </listitem> 237 </varlistentry> 238 239 <varlistentry> 240 <term><varname>AllowedCPUs=</varname></term> 241 <term><varname>StartupAllowedCPUs=</varname></term> 242 243 <listitem> 244 <para>Restrict processes to be executed on specific CPUs. Takes a list of CPU indices or ranges separated by either 245 whitespace or commas. CPU ranges are specified by the lower and upper CPU indices separated by a dash.</para> 246 247 <para>Setting <varname>AllowedCPUs=</varname> or <varname>StartupAllowedCPUs=</varname> doesn't guarantee that all 248 of the CPUs will be used by the processes as it may be limited by parent units. The effective configuration is 249 reported as <varname>EffectiveCPUs=</varname>.</para> 250 251 <para>While <varname>StartupAllowedCPUs=</varname> applies to the startup and shutdown phases of the system, 252 <varname>AllowedCPUs=</varname> applies to normal runtime of the system, and if the former is not set also to 253 the startup and shutdown phases. Using <varname>StartupAllowedCPUs=</varname> allows prioritizing specific services at 254 boot-up and shutdown differently than during normal runtime.</para> 255 256 <para>This setting is supported only with the unified control group hierarchy.</para> 257 </listitem> 258 </varlistentry> 259 260 <varlistentry> 261 <term><varname>AllowedMemoryNodes=</varname></term> 262 <term><varname>StartupAllowedMemoryNodes=</varname></term> 263 264 <listitem> 265 <para>Restrict processes to be executed on specific memory NUMA nodes. Takes a list of memory NUMA nodes indices 266 or ranges separated by either whitespace or commas. Memory NUMA nodes ranges are specified by the lower and upper 267 NUMA nodes indices separated by a dash.</para> 268 269 <para>Setting <varname>AllowedMemoryNodes=</varname> or <varname>StartupAllowedMemoryNodes=</varname> doesn't 270 guarantee that all of the memory NUMA nodes will be used by the processes as it may be limited by parent units. 271 The effective configuration is reported as <varname>EffectiveMemoryNodes=</varname>.</para> 272 273 <para>While <varname>StartupAllowedMemoryNodes=</varname> applies to the startup and shutdown phases of the system, 274 <varname>AllowedMemoryNodes=</varname> applies to normal runtime of the system, and if the former is not set also to 275 the startup and shutdown phases. Using <varname>StartupAllowedMemoryNodes=</varname> allows prioritizing specific services at 276 boot-up and shutdown differently than during normal runtime.</para> 277 278 <para>This setting is supported only with the unified control group hierarchy.</para> 279 </listitem> 280 </varlistentry> 281 282 <varlistentry> 283 <term><varname>MemoryAccounting=</varname></term> 284 285 <listitem> 286 <para>Turn on process and kernel memory accounting for this 287 unit. Takes a boolean argument. Note that turning on memory 288 accounting for one unit will also implicitly turn it on for 289 all units contained in the same slice and for all its parent 290 slices and the units contained therein. The system default 291 for this setting may be controlled with 292 <varname>DefaultMemoryAccounting=</varname> in 293 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 294 </listitem> 295 </varlistentry> 296 297 <varlistentry> 298 <term><varname>MemoryMin=<replaceable>bytes</replaceable></varname>, <varname>MemoryLow=<replaceable>bytes</replaceable></varname></term> 299 300 <listitem> 301 <para>Specify the memory usage protection of the executed processes in this unit. 302 When reclaiming memory, the unit is treated as if it was using less memory resulting in memory 303 to be preferentially reclaimed from unprotected units. 304 Using <varname>MemoryLow=</varname> results in a weaker protection where memory may still 305 be reclaimed to avoid invoking the OOM killer in case there is no other reclaimable memory.</para> 306 <para> 307 For a protection to be effective, it is generally required to set a corresponding 308 allocation on all ancestors, which is then distributed between children 309 (with the exception of the root slice). 310 Any <varname>MemoryMin=</varname> or <varname>MemoryLow=</varname> allocation that is not 311 explicitly distributed to specific children is used to create a shared protection for all children. 312 As this is a shared protection, the children will freely compete for the memory.</para> 313 314 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is 315 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a 316 percentage value may be specified, which is taken relative to the installed physical memory on the 317 system. If assigned the special value <literal>infinity</literal>, all available memory is protected, which may be 318 useful in order to always inherit all of the protection afforded by ancestors. 319 This controls the <literal>memory.min</literal> or <literal>memory.low</literal> control group attribute. 320 For details about this control group attribute, see <ulink 321 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files</ulink>.</para> 322 323 <para>This setting is supported only if the unified control group hierarchy is used and disables 324 <varname>MemoryLimit=</varname>.</para> 325 326 <para>Units may have their children use a default <literal>memory.min</literal> or 327 <literal>memory.low</literal> value by specifying <varname>DefaultMemoryMin=</varname> or 328 <varname>DefaultMemoryLow=</varname>, which has the same semantics as 329 <varname>MemoryMin=</varname> and <varname>MemoryLow=</varname>. 330 This setting does not affect <literal>memory.min</literal> or <literal>memory.low</literal> 331 in the unit itself. 332 Using it to set a default child allocation is only useful on kernels older than 5.7, 333 which do not support the <literal>memory_recursiveprot</literal> cgroup2 mount option.</para> 334 </listitem> 335 </varlistentry> 336 337 <varlistentry> 338 <term><varname>MemoryHigh=<replaceable>bytes</replaceable></varname></term> 339 340 <listitem> 341 <para>Specify the throttling limit on memory usage of the executed processes in this unit. Memory usage may go 342 above the limit if unavoidable, but the processes are heavily slowed down and memory is taken away 343 aggressively in such cases. This is the main mechanism to control memory usage of a unit.</para> 344 345 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is 346 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a 347 percentage value may be specified, which is taken relative to the installed physical memory on the 348 system. If assigned the 349 special value <literal>infinity</literal>, no memory throttling is applied. This controls the 350 <literal>memory.high</literal> control group attribute. For details about this control group attribute, see 351 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files</ulink>.</para> 352 353 <para>This setting is supported only if the unified control group hierarchy is used and disables 354 <varname>MemoryLimit=</varname>.</para> 355 </listitem> 356 </varlistentry> 357 358 <varlistentry> 359 <term><varname>MemoryMax=<replaceable>bytes</replaceable></varname></term> 360 361 <listitem> 362 <para>Specify the absolute limit on memory usage of the executed processes in this unit. If memory usage 363 cannot be contained under the limit, out-of-memory killer is invoked inside the unit. It is recommended to 364 use <varname>MemoryHigh=</varname> as the main control mechanism and use <varname>MemoryMax=</varname> as the 365 last line of defense.</para> 366 367 <para>Takes a memory size in bytes. If the value is suffixed with K, M, G or T, the specified memory size is 368 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. Alternatively, a 369 percentage value may be specified, which is taken relative to the installed physical memory on the system. If 370 assigned the special value <literal>infinity</literal>, no memory limit is applied. This controls the 371 <literal>memory.max</literal> control group attribute. For details about this control group attribute, see 372 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files</ulink>.</para> 373 374 <para>This setting replaces <varname>MemoryLimit=</varname>.</para> 375 </listitem> 376 </varlistentry> 377 378 <varlistentry> 379 <term><varname>MemorySwapMax=<replaceable>bytes</replaceable></varname></term> 380 381 <listitem> 382 <para>Specify the absolute limit on swap usage of the executed processes in this unit.</para> 383 384 <para>Takes a swap size in bytes. If the value is suffixed with K, M, G or T, the specified swap size is 385 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes (with the base 1024), respectively. If assigned the 386 special value <literal>infinity</literal>, no swap limit is applied. This controls the 387 <literal>memory.swap.max</literal> control group attribute. For details about this control group attribute, 388 see <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory-interface-files">Memory Interface Files</ulink>.</para> 389 390 <para>This setting is supported only if the unified control group hierarchy is used and disables 391 <varname>MemoryLimit=</varname>.</para> 392 </listitem> 393 </varlistentry> 394 395 <varlistentry> 396 <term><varname>TasksAccounting=</varname></term> 397 398 <listitem> 399 <para>Turn on task accounting for this unit. Takes a 400 boolean argument. If enabled, the system manager will keep 401 track of the number of tasks in the unit. The number of 402 tasks accounted this way includes both kernel threads and 403 userspace processes, with each thread counting 404 individually. Note that turning on tasks accounting for one 405 unit will also implicitly turn it on for all units contained 406 in the same slice and for all its parent slices and the 407 units contained therein. The system default for this setting 408 may be controlled with 409 <varname>DefaultTasksAccounting=</varname> in 410 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 411 </listitem> 412 </varlistentry> 413 414 <varlistentry> 415 <term><varname>TasksMax=<replaceable>N</replaceable></varname></term> 416 417 <listitem> 418 <para>Specify the maximum number of tasks that may be created in the unit. This ensures that the number of 419 tasks accounted for the unit (see above) stays below a specific limit. This either takes an absolute number 420 of tasks or a percentage value that is taken relative to the configured maximum number of tasks on the 421 system. If assigned the special value <literal>infinity</literal>, no tasks limit is applied. This controls 422 the <literal>pids.max</literal> control group attribute. For details about this control group attribute, see 423 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/pids.html">Process Number Controller</ulink>. 424 </para> 425 426 <para>The system default for this setting may be controlled with 427 <varname>DefaultTasksMax=</varname> in 428 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 429 </listitem> 430 </varlistentry> 431 432 <varlistentry> 433 <term><varname>IOAccounting=</varname></term> 434 435 <listitem> 436 <para>Turn on Block I/O accounting for this unit, if the unified control group hierarchy is used on the 437 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly 438 turn it on for all units contained in the same slice and all for its parent slices and the units contained 439 therein. The system default for this setting may be controlled with <varname>DefaultIOAccounting=</varname> 440 in 441 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 442 443 <para>This setting replaces <varname>BlockIOAccounting=</varname> and disables settings prefixed with 444 <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para> 445 </listitem> 446 </varlistentry> 447 448 <varlistentry> 449 <term><varname>IOWeight=<replaceable>weight</replaceable></varname></term> 450 <term><varname>StartupIOWeight=<replaceable>weight</replaceable></varname></term> 451 452 <listitem> 453 <para>Set the default overall block I/O weight for the executed processes, if the unified control 454 group hierarchy is used on the system. Takes a single weight value (between 1 and 10000) to set the 455 default block I/O weight. This controls the <literal>io.weight</literal> control group attribute, 456 which defaults to 100. For details about this control group attribute, see <ulink 457 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO 458 Interface Files</ulink>. The available I/O bandwidth is split up among all units within one slice 459 relative to their block I/O weight. A higher weight means more I/O bandwidth, a lower weight means 460 less.</para> 461 462 <para>While <varname>StartupIOWeight=</varname> applies 463 to the startup and shutdown phases of the system, 464 <varname>IOWeight=</varname> applies to the later runtime of 465 the system, and if the former is not set also to the startup 466 and shutdown phases. This allows prioritizing specific services at boot-up 467 and shutdown differently than during runtime.</para> 468 469 <para>These settings replace <varname>BlockIOWeight=</varname> and <varname>StartupBlockIOWeight=</varname> 470 and disable settings prefixed with <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para> 471 </listitem> 472 </varlistentry> 473 474 <varlistentry> 475 <term><varname>IODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term> 476 477 <listitem> 478 <para>Set the per-device overall block I/O weight for the executed processes, if the unified control group 479 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify 480 the device specific weight value, between 1 and 10000. (Example: <literal>/dev/sda 1000</literal>). The file 481 path may be specified as path to a block device node or as any other file, in which case the backing block 482 device of the file system of the file is determined. This controls the <literal>io.weight</literal> control 483 group attribute, which defaults to 100. Use this option multiple times to set weights for multiple devices. 484 For details about this control group attribute, see <ulink 485 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files</ulink>.</para> 486 487 <para>This setting replaces <varname>BlockIODeviceWeight=</varname> and disables settings prefixed with 488 <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para> 489 490 <para>The specified device node should reference a block device that has an I/O scheduler 491 associated, i.e. should not refer to partition or loopback block devices, but to the originating, 492 physical device. When a path to a regular file or directory is specified it is attempted to 493 discover the correct originating device backing the file system of the specified path. This works 494 correctly only for simpler cases, where the file system is directly placed on a partition or 495 physical block device, or where simple 1:1 encryption using dm-crypt/LUKS is used. This discovery 496 does not cover complex storage and in particular RAID and volume management storage devices.</para> 497 </listitem> 498 </varlistentry> 499 500 <varlistentry> 501 <term><varname>IOReadBandwidthMax=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term> 502 <term><varname>IOWriteBandwidthMax=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term> 503 504 <listitem> 505 <para>Set the per-device overall block I/O bandwidth maximum limit for the executed processes, if the unified 506 control group hierarchy is used on the system. This limit is not work-conserving and the executed processes 507 are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of a file 508 path and a bandwidth value (in bytes per second) to specify the device specific bandwidth. The file path may 509 be a path to a block device node, or as any other file in which case the backing block device of the file 510 system of the file is used. If the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is 511 parsed as Kilobytes, Megabytes, Gigabytes, or Terabytes, respectively, to the base of 1000. (Example: 512 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the <literal>io.max</literal> control 513 group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For details 514 about this control group attribute, see <ulink 515 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files</ulink>. 516 </para> 517 518 <para>These settings replace <varname>BlockIOReadBandwidth=</varname> and 519 <varname>BlockIOWriteBandwidth=</varname> and disable settings prefixed with <varname>BlockIO</varname> or 520 <varname>StartupBlockIO</varname>.</para> 521 522 <para>Similar restrictions on block device discovery as for <varname>IODeviceWeight=</varname> apply, see above.</para> 523 </listitem> 524 </varlistentry> 525 526 <varlistentry> 527 <term><varname>IOReadIOPSMax=<replaceable>device</replaceable> <replaceable>IOPS</replaceable></varname></term> 528 <term><varname>IOWriteIOPSMax=<replaceable>device</replaceable> <replaceable>IOPS</replaceable></varname></term> 529 530 <listitem> 531 <para>Set the per-device overall block I/O IOs-Per-Second maximum limit for the executed processes, if the 532 unified control group hierarchy is used on the system. This limit is not work-conserving and the executed 533 processes are not allowed to use more even if the device has idle capacity. Takes a space-separated pair of 534 a file path and an IOPS value to specify the device specific IOPS. The file path may be a path to a block 535 device node, or as any other file in which case the backing block device of the file system of the file is 536 used. If the IOPS is suffixed with K, M, G, or T, the specified IOPS is parsed as KiloIOPS, MegaIOPS, 537 GigaIOPS, or TeraIOPS, respectively, to the base of 1000. (Example: 538 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 1K"). This controls the <literal>io.max</literal> control 539 group attributes. Use this option multiple times to set IOPS limits for multiple devices. For details about 540 this control group attribute, see <ulink 541 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files</ulink>. 542 </para> 543 544 <para>These settings are supported only if the unified control group hierarchy is used and disable settings 545 prefixed with <varname>BlockIO</varname> or <varname>StartupBlockIO</varname>.</para> 546 547 <para>Similar restrictions on block device discovery as for <varname>IODeviceWeight=</varname> apply, see above.</para> 548 </listitem> 549 </varlistentry> 550 551 <varlistentry> 552 <term><varname>IODeviceLatencyTargetSec=<replaceable>device</replaceable> <replaceable>target</replaceable></varname></term> 553 554 <listitem> 555 <para>Set the per-device average target I/O latency for the executed processes, if the unified control group 556 hierarchy is used on the system. Takes a file path and a timespan separated by a space to specify 557 the device specific latency target. (Example: "/dev/sda 25ms"). The file path may be specified 558 as path to a block device node or as any other file, in which case the backing block device of the file 559 system of the file is determined. This controls the <literal>io.latency</literal> control group 560 attribute. Use this option multiple times to set latency target for multiple devices. For details about this 561 control group attribute, see <ulink 562 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#io-interface-files">IO Interface Files</ulink>.</para> 563 564 <para>Implies <literal>IOAccounting=yes</literal>.</para> 565 566 <para>These settings are supported only if the unified control group hierarchy is used.</para> 567 568 <para>Similar restrictions on block device discovery as for <varname>IODeviceWeight=</varname> apply, see above.</para> 569 </listitem> 570 </varlistentry> 571 572 <varlistentry> 573 <term><varname>IPAccounting=</varname></term> 574 575 <listitem> 576 <para>Takes a boolean argument. If true, turns on IPv4 and IPv6 network traffic accounting for packets sent 577 or received by the unit. When this option is turned on, all IPv4 and IPv6 sockets created by any process of 578 the unit are accounted for.</para> 579 580 <para>When this option is used in socket units, it applies to all IPv4 and IPv6 sockets 581 associated with it (including both listening and connection sockets where this applies). Note that for 582 socket-activated services, this configuration setting and the accounting data of the service unit and the 583 socket unit are kept separate, and displayed separately. No propagation of the setting and the collected 584 statistics is done, in either direction. Moreover, any traffic sent or received on any of the socket unit's 585 sockets is accounted to the socket unit — and never to the service unit it might have activated, even if the 586 socket is used by it.</para> 587 588 <para>The system default for this setting may be controlled with <varname>DefaultIPAccounting=</varname> in 589 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 590 </listitem> 591 </varlistentry> 592 593 <varlistentry> 594 <term><varname>IPAddressAllow=<replaceable>ADDRESS[/PREFIXLENGTH]…</replaceable></varname></term> 595 <term><varname>IPAddressDeny=<replaceable>ADDRESS[/PREFIXLENGTH]…</replaceable></varname></term> 596 597 <listitem> 598 <para>Turn on network traffic filtering for IP packets sent and received over 599 <constant>AF_INET</constant> and <constant>AF_INET6</constant> sockets. Both directives take a 600 space separated list of IPv4 or IPv6 addresses, each optionally suffixed with an address prefix 601 length in bits after a <literal>/</literal> character. If the suffix is omitted, the address is 602 considered a host address, i.e. the filter covers the whole address (32 bits for IPv4, 128 bits for 603 IPv6).</para> 604 605 <para>The access lists configured with this option are applied to all sockets created by processes 606 of this unit (or in the case of socket units, associated with it). The lists are implicitly 607 combined with any lists configured for any of the parent slice units this unit might be a member 608 of. By default both access lists are empty. Both ingress and egress traffic is filtered by these 609 settings. In case of ingress traffic the source IP address is checked against these access lists, 610 in case of egress traffic the destination IP address is checked. The following rules are applied in 611 turn:</para> 612 613 <itemizedlist> 614 <listitem><para>Access is granted when the checked IP address matches an entry in the 615 <varname>IPAddressAllow=</varname> list.</para></listitem> 616 617 <listitem><para>Otherwise, access is denied when the checked IP address matches an entry in the 618 <varname>IPAddressDeny=</varname> list.</para></listitem> 619 620 <listitem><para>Otherwise, access is granted.</para></listitem> 621 </itemizedlist> 622 623 <para>In order to implement an allow-listing IP firewall, it is recommended to use a 624 <varname>IPAddressDeny=</varname><constant>any</constant> setting on an upper-level slice unit 625 (such as the root slice <filename>-.slice</filename> or the slice containing all system services 626 <filename>system.slice</filename> – see 627 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> 628 for details on these slice units), plus individual per-service <varname>IPAddressAllow=</varname> 629 lines permitting network access to relevant services, and only them.</para> 630 631 <para>Note that for socket-activated services, the IP access list configured on the socket unit 632 applies to all sockets associated with it directly, but not to any sockets created by the 633 ultimately activated services for it. Conversely, the IP access list configured for the service is 634 not applied to any sockets passed into the service via socket activation. Thus, it is usually a 635 good idea to replicate the IP access lists on both the socket and the service unit. Nevertheless, 636 it may make sense to maintain one list more open and the other one more restricted, depending on 637 the usecase.</para> 638 639 <para>If these settings are used multiple times in the same unit the specified lists are combined. If an 640 empty string is assigned to these settings the specific access list is reset and all previous settings undone.</para> 641 642 <para>In place of explicit IPv4 or IPv6 address and prefix length specifications a small set of symbolic 643 names may be used. The following names are defined:</para> 644 645 <table> 646 <title>Special address/network names</title> 647 648 <tgroup cols='3'> 649 <colspec colname='name'/> 650 <colspec colname='definition'/> 651 <colspec colname='meaning'/> 652 653 <thead> 654 <row> 655 <entry>Symbolic Name</entry> 656 <entry>Definition</entry> 657 <entry>Meaning</entry> 658 </row> 659 </thead> 660 661 <tbody> 662 <row> 663 <entry><constant>any</constant></entry> 664 <entry>0.0.0.0/0 ::/0</entry> 665 <entry>Any host</entry> 666 </row> 667 668 <row> 669 <entry><constant>localhost</constant></entry> 670 <entry>127.0.0.0/8 ::1/128</entry> 671 <entry>All addresses on the local loopback</entry> 672 </row> 673 674 <row> 675 <entry><constant>link-local</constant></entry> 676 <entry>169.254.0.0/16 fe80::/64</entry> 677 <entry>All link-local IP addresses</entry> 678 </row> 679 680 <row> 681 <entry><constant>multicast</constant></entry> 682 <entry>224.0.0.0/4 ff00::/8</entry> 683 <entry>All IP multicasting addresses</entry> 684 </row> 685 </tbody> 686 </tgroup> 687 </table> 688 689 <para>Note that these settings might not be supported on some systems (for example if eBPF control group 690 support is not enabled in the underlying kernel or container manager). These settings will have no effect in 691 that case. If compatibility with such systems is desired it is hence recommended to not exclusively rely on 692 them for IP security.</para> 693 </listitem> 694 </varlistentry> 695 696 <varlistentry> 697 <term><varname>IPIngressFilterPath=<replaceable>BPF_FS_PROGRAM_PATH</replaceable></varname></term> 698 <term><varname>IPEgressFilterPath=<replaceable>BPF_FS_PROGRAM_PATH</replaceable></varname></term> 699 700 <listitem> 701 <para>Add custom network traffic filters implemented as BPF programs, applying to all IP packets 702 sent and received over <constant>AF_INET</constant> and <constant>AF_INET6</constant> sockets. 703 Takes an absolute path to a pinned BPF program in the BPF virtual filesystem (<filename>/sys/fs/bpf/</filename>). 704 </para> 705 706 <para>The filters configured with this option are applied to all sockets created by processes 707 of this unit (or in the case of socket units, associated with it). The filters are loaded in addition 708 to filters any of the parent slice units this unit might be a member of as well as any 709 <varname>IPAddressAllow=</varname> and <varname>IPAddressDeny=</varname> filters in any of these units. 710 By default there are no filters specified.</para> 711 712 <para>If these settings are used multiple times in the same unit all the specified programs are attached. If an 713 empty string is assigned to these settings the program list is reset and all previous specified programs ignored.</para> 714 715 <para>If the path <replaceable>BPF_FS_PROGRAM_PATH</replaceable> in <varname>IPIngressFilterPath=</varname> assignment 716 is already being handled by <varname>BPFProgram=</varname> ingress hook, e.g. 717 <varname>BPFProgram=</varname><constant>ingress</constant>:<replaceable>BPF_FS_PROGRAM_PATH</replaceable>, 718 the assignment will be still considered valid and the program will be attached to a cgroup. Same for 719 <varname>IPEgressFilterPath=</varname> path and <constant>egress</constant> hook.</para> 720 721 <para>Note that for socket-activated services, the IP filter programs configured on the socket unit apply to 722 all sockets associated with it directly, but not to any sockets created by the ultimately activated services 723 for it. Conversely, the IP filter programs configured for the service are not applied to any sockets passed into 724 the service via socket activation. Thus, it is usually a good idea, to replicate the IP filter programs on both 725 the socket and the service unit, however it often makes sense to maintain one configuration more open and the other 726 one more restricted, depending on the usecase.</para> 727 728 <para>Note that these settings might not be supported on some systems (for example if eBPF control group 729 support is not enabled in the underlying kernel or container manager). These settings will fail the service in 730 that case. If compatibility with such systems is desired it is hence recommended to attach your filter manually 731 (requires <varname>Delegate=</varname><constant>yes</constant>) instead of using this setting.</para> 732 </listitem> 733 </varlistentry> 734 735 <varlistentry> 736 <term><varname>BPFProgram=<replaceable>type</replaceable><constant>:</constant><replaceable>program-path</replaceable></varname></term> 737 <listitem> 738 <para>Add a custom cgroup BPF program.</para> 739 740 <para><varname>BPFProgram=</varname> allows attaching BPF hooks to the cgroup of a systemd unit. 741 (This generalizes the functionality exposed via <varname>IPEgressFilterPath=</varname> for egress and 742 <varname>IPIngressFilterPath=</varname> for ingress.) 743 Cgroup-bpf hooks in the form of BPF programs loaded to the BPF filesystem are attached with cgroup-bpf attach 744 flags determined by the unit. For details about attachment types and flags see <ulink 745 url="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/include/uapi/linux/bpf.h"/>. 746 For general BPF documentation please refer to <ulink url="https://www.kernel.org/doc/html/latest/bpf/index.html"/>.</para> 747 748 <para>The specification of BPF program consists of a <replaceable>type</replaceable> followed by a 749 <replaceable>program-path</replaceable> with <literal>:</literal> as the separator: 750 <replaceable>type</replaceable><constant>:</constant><replaceable>program-path</replaceable>.</para> 751 752 <para><replaceable>type</replaceable> is the string name of BPF attach type also used in 753 <command>bpftool</command>. <replaceable>type</replaceable> can be one of <constant>egress</constant>, 754 <constant>ingress</constant>, <constant>sock_create</constant>, <constant>sock_ops</constant>, 755 <constant>device</constant>, <constant>bind4</constant>, <constant>bind6</constant>, 756 <constant>connect4</constant>, <constant>connect6</constant>, <constant>post_bind4</constant>, 757 <constant>post_bind6</constant>, <constant>sendmsg4</constant>, <constant>sendmsg6</constant>, 758 <constant>sysctl</constant>, <constant>recvmsg4</constant>, <constant>recvmsg6</constant>, 759 <constant>getsockopt</constant>, <constant>setsockopt</constant>.</para> 760 761 <para>Setting <varname>BPFProgram=</varname> to an empty value makes previous assignments ineffective.</para> 762 <para>Multiple assignments of the same <replaceable>type</replaceable>:<replaceable>program-path</replaceable> 763 value have the same effect as a single assignment: the program with the path <replaceable>program-path</replaceable> 764 will be attached to cgroup hook <replaceable>type</replaceable> just once.</para> 765 <para>If BPF <constant>egress</constant> pinned to <replaceable>program-path</replaceable> path is already being 766 handled by <varname>IPEgressFilterPath=</varname>, <varname>BPFProgram=</varname> 767 assignment will be considered valid and <varname>BPFProgram=</varname> will be attached to a cgroup. 768 Similarly for <constant>ingress</constant> hook and <varname>IPIngressFilterPath=</varname> assignment.</para> 769 770 <para>BPF programs passed with <varname>BPFProgram=</varname> are attached to the cgroup of a unit with BPF 771 attach flag <constant>multi</constant>, that allows further attachments of the same 772 <replaceable>type</replaceable> within cgroup hierarchy topped by the unit cgroup.</para> 773 774 <para>Examples:<programlisting> 775BPFProgram=egress:/sys/fs/bpf/egress-hook 776BPFProgram=bind6:/sys/fs/bpf/sock-addr-hook 777</programlisting></para> 778 </listitem> 779 </varlistentry> 780 781 <varlistentry> 782 <term><varname>SocketBindAllow=<replaceable>bind-rule</replaceable></varname></term> 783 <term><varname>SocketBindDeny=<replaceable>bind-rule</replaceable></varname></term> 784 785 <listitem> 786 <para>Allow or deny binding a socket address to a socket by matching it with the <replaceable>bind-rule</replaceable> and 787 applying a corresponding action if there is a match.</para> 788 789 <para><replaceable>bind-rule</replaceable> describes socket properties such as <replaceable>address-family</replaceable>, 790 <replaceable>transport-protocol</replaceable> and <replaceable>ip-ports</replaceable>.</para> 791 792 <para><replaceable>bind-rule</replaceable> := 793 { [<replaceable>address-family</replaceable><constant>:</constant>][<replaceable>transport-protocol</replaceable><constant>:</constant>][<replaceable>ip-ports</replaceable>] | <constant>any</constant> }</para> 794 795 <para><replaceable>address-family</replaceable> := { <constant>ipv4</constant> | <constant>ipv6</constant> }</para> 796 797 <para><replaceable>transport-protocol</replaceable> := { <constant>tcp</constant> | <constant>udp</constant> }</para> 798 799 <para><replaceable>ip-ports</replaceable> := { <replaceable>ip-port</replaceable> | <replaceable>ip-port-range</replaceable> }</para> 800 801 <para>An optional <replaceable>address-family</replaceable> expects <constant>ipv4</constant> or <constant>ipv6</constant> values. 802 If not specified, a rule will be matched for both IPv4 and IPv6 addresses and applied depending on other socket fields, e.g. <replaceable>transport-protocol</replaceable>, 803 <replaceable>ip-port</replaceable>.</para> 804 805 <para>An optional <replaceable>transport-protocol</replaceable> expects <constant>tcp</constant> or <constant>udp</constant> transport protocol names. 806 If not specified, a rule will be matched for any transport protocol.</para> 807 808 <para>An optional <replaceable>ip-port</replaceable> value must lie within 1…65535 interval inclusively, i.e. 809 dynamic port <constant>0</constant> is not allowed. A range of sequential ports is described by 810 <replaceable>ip-port-range</replaceable> := <replaceable>ip-port-low</replaceable><constant>-</constant><replaceable>ip-port-high</replaceable>, 811 where <replaceable>ip-port-low</replaceable> is smaller than or equal to <replaceable>ip-port-high</replaceable> 812 and both are within 1…65535 inclusively.</para> 813 814 <para>A special value <constant>any</constant> can be used to apply a rule to any address family, transport protocol and any port with a positive value.</para> 815 816 <para>To allow multiple rules assign <varname>SocketBindAllow=</varname> or <varname>SocketBindDeny=</varname> multiple times. 817 To clear the existing assignments pass an empty <varname>SocketBindAllow=</varname> or <varname>SocketBindDeny=</varname> 818 assignment.</para> 819 820 <para>For each of <varname>SocketBindAllow=</varname> and <varname>SocketBindDeny=</varname>, maximum allowed number of assignments is 821 <constant>128</constant>.</para> 822 823 <itemizedlist> 824 <listitem><para>Binding to a socket is allowed when a socket address matches an entry in the 825 <varname>SocketBindAllow=</varname> list.</para></listitem> 826 827 <listitem><para>Otherwise, binding is denied when the socket address matches an entry in the 828 <varname>SocketBindDeny=</varname> list.</para></listitem> 829 830 <listitem><para>Otherwise, binding is allowed.</para></listitem> 831 </itemizedlist> 832 833 <para>The feature is implemented with <constant>cgroup/bind4</constant> and <constant>cgroup/bind6</constant> cgroup-bpf hooks.</para> 834 <para>Examples:<programlisting>… 835# Allow binding IPv6 socket addresses with a port greater than or equal to 10000. 836[Service] 837SocketBindAllow=ipv6:10000-65535 838SocketBindDeny=any 839… 840# Allow binding IPv4 and IPv6 socket addresses with 1234 and 4321 ports. 841[Service] 842SocketBindAllow=1234 843SocketBindAllow=4321 844SocketBindDeny=any 845… 846# Deny binding IPv6 socket addresses. 847[Service] 848SocketBindDeny=ipv6 849… 850# Deny binding IPv4 and IPv6 socket addresses. 851[Service] 852SocketBindDeny=any 853… 854# Allow binding only over TCP 855[Service] 856SocketBindAllow=tcp 857SocketBindDeny=any 858… 859# Allow binding only over IPv6/TCP 860[Service] 861SocketBindAllow=ipv6:tcp 862SocketBindDeny=any 863… 864# Allow binding ports within 10000-65535 range over IPv4/UDP. 865[Service] 866SocketBindAllow=ipv4:udp:10000-65535 867SocketBindDeny=any 868…</programlisting></para> 869 </listitem> 870 </varlistentry> 871 872 <varlistentry> 873 <term><varname>RestrictNetworkInterfaces=</varname></term> 874 875 <listitem> 876 <para>Takes a list of space-separated network interface names. This option restricts the network 877 interfaces that processes of this unit can use. By default processes can only use the network interfaces 878 listed (allow-list). If the first character of the rule is <literal>~</literal>, the effect is inverted: 879 the processes can only use network interfaces not listed (deny-list). 880 </para> 881 882 <para>This option can appear multiple times, in which case the network interface names are merged. If the 883 empty string is assigned the set is reset, all prior assignments will have not effect. 884 </para> 885 886 <para>If you specify both types of this option (i.e. allow-listing and deny-listing), the first encountered 887 will take precedence and will dictate the default action (allow vs deny). Then the next occurrences of this 888 option will add or delete the listed network interface names from the set, depending of its type and the 889 default action. 890 </para> 891 892 <para>The loopback interface ("lo") is not treated in any special way, you have to configure it explicitly 893 in the unit file. 894 </para> 895 <para>Example 1: allow-list 896 <programlisting> 897RestrictNetworkInterfaces=eth1 898RestrictNetworkInterfaces=eth2</programlisting> 899 Programs in the unit will be only able to use the eth1 and eth2 network 900 interfaces. 901 </para> 902 903 <para>Example 2: deny-list 904 <programlisting> 905RestrictNetworkInterfaces=~eth1 eth2</programlisting> 906 Programs in the unit will be able to use any network interface but eth1 and eth2. 907 </para> 908 909 <para>Example 3: mixed 910 <programlisting> 911RestrictNetworkInterfaces=eth1 eth2 912RestrictNetworkInterfaces=~eth1</programlisting> 913 Programs in the unit will be only able to use the eth2 network interface. 914 </para> 915 </listitem> 916 </varlistentry> 917 918 <varlistentry> 919 <term><varname>DeviceAllow=</varname></term> 920 921 <listitem> 922 <para>Control access to specific device nodes by the executed processes. Takes two space-separated 923 strings: a device node specifier followed by a combination of <constant>r</constant>, 924 <constant>w</constant>, <constant>m</constant> to control <emphasis>r</emphasis>eading, 925 <emphasis>w</emphasis>riting, or creation of the specific device node(s) by the unit 926 (<emphasis>m</emphasis>knod), respectively. On cgroup-v1 this controls the 927 <literal>devices.allow</literal> control group attribute. For details about this control group 928 attribute, see <ulink 929 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/devices.html">Device Whitelist Controller</ulink>. 930 In the unified cgroup hierarchy this functionality is implemented using eBPF filtering.</para> 931 932 <para>When access to <emphasis>all</emphasis> physical devices should be disallowed, 933 <varname>PrivateDevices=</varname> may be used instead. See 934 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. 935 </para> 936 937 <para>The device node specifier is either a path to a device node in the file system, starting with 938 <filename>/dev/</filename>, or a string starting with either <literal>char-</literal> or 939 <literal>block-</literal> followed by a device group name, as listed in 940 <filename>/proc/devices</filename>. The latter is useful to allow-list all current and future 941 devices belonging to a specific device group at once. The device group is matched according to 942 filename globbing rules, you may hence use the <literal>*</literal> and <literal>?</literal> 943 wildcards. (Note that such globbing wildcards are not available for device node path 944 specifications!) In order to match device nodes by numeric major/minor, use device node paths in 945 the <filename>/dev/char/</filename> and <filename>/dev/block/</filename> directories. However, 946 matching devices by major/minor is generally not recommended as assignments are neither stable nor 947 portable between systems or different kernel versions.</para> 948 949 <para>Examples: <filename>/dev/sda5</filename> is a path to a device node, referring to an ATA or 950 SCSI block device. <literal>char-pts</literal> and <literal>char-alsa</literal> are specifiers for 951 all pseudo TTYs and all ALSA sound devices, respectively. <literal>char-cpu/*</literal> is a 952 specifier matching all CPU related device groups.</para> 953 954 <para>Note that allow lists defined this way should only reference device groups which are 955 resolvable at the time the unit is started. Any device groups not resolvable then are not added to 956 the device allow list. In order to work around this limitation, consider extending service units 957 with a pair of <command>After=modprobe@xyz.service</command> and 958 <command>Wants=modprobe@xyz.service</command> lines that load the necessary kernel module 959 implementing the device group if missing. 960 Example: <programlisting>… 961[Unit] 962Wants=modprobe@loop.service 963After=modprobe@loop.service 964 965[Service] 966DeviceAllow=block-loop 967DeviceAllow=/dev/loop-control 968…</programlisting></para> 969 970 </listitem> 971 </varlistentry> 972 973 <varlistentry> 974 <term><varname>DevicePolicy=auto|closed|strict</varname></term> 975 976 <listitem> 977 <para> 978 Control the policy for allowing device access: 979 </para> 980 <variablelist> 981 <varlistentry> 982 <term><option>strict</option></term> 983 <listitem> 984 <para>means to only allow types of access that are 985 explicitly specified.</para> 986 </listitem> 987 </varlistentry> 988 989 <varlistentry> 990 <term><option>closed</option></term> 991 <listitem> 992 <para>in addition, allows access to standard pseudo 993 devices including 994 <filename>/dev/null</filename>, 995 <filename>/dev/zero</filename>, 996 <filename>/dev/full</filename>, 997 <filename>/dev/random</filename>, and 998 <filename>/dev/urandom</filename>. 999 </para> 1000 </listitem> 1001 </varlistentry> 1002 1003 <varlistentry> 1004 <term><option>auto</option></term> 1005 <listitem> 1006 <para> 1007 in addition, allows access to all devices if no 1008 explicit <varname>DeviceAllow=</varname> is present. 1009 This is the default. 1010 </para> 1011 </listitem> 1012 </varlistentry> 1013 </variablelist> 1014 </listitem> 1015 </varlistentry> 1016 1017 <varlistentry> 1018 <term><varname>Slice=</varname></term> 1019 1020 <listitem> 1021 <para>The name of the slice unit to place the unit 1022 in. Defaults to <filename>system.slice</filename> for all 1023 non-instantiated units of all unit types (except for slice 1024 units themselves see below). Instance units are by default 1025 placed in a subslice of <filename>system.slice</filename> 1026 that is named after the template name.</para> 1027 1028 <para>This option may be used to arrange systemd units in a 1029 hierarchy of slices each of which might have resource 1030 settings applied.</para> 1031 1032 <para>For units of type slice, the only accepted value for 1033 this setting is the parent slice. Since the name of a slice 1034 unit implies the parent slice, it is hence redundant to ever 1035 set this parameter directly for slice units.</para> 1036 1037 <para>Special care should be taken when relying on the default slice assignment in templated service units 1038 that have <varname>DefaultDependencies=no</varname> set, see 1039 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, section 1040 "Default Dependencies" for details.</para> 1041 1042 </listitem> 1043 </varlistentry> 1044 1045 <varlistentry> 1046 <term><varname>Delegate=</varname></term> 1047 1048 <listitem> 1049 <para>Turns on delegation of further resource control partitioning to processes of the unit. Units where this 1050 is enabled may create and manage their own private subhierarchy of control groups below the control group of 1051 the unit itself. For unprivileged services (i.e. those using the <varname>User=</varname> setting) the unit's 1052 control group will be made accessible to the relevant user. When enabled the service manager will refrain 1053 from manipulating control groups or moving processes below the unit's control group, so that a clear concept 1054 of ownership is established: the control group tree above the unit's control group (i.e. towards the root 1055 control group) is owned and managed by the service manager of the host, while the control group tree below 1056 the unit's control group is owned and managed by the unit itself. Takes either a boolean argument or a list 1057 of control group controller names. If true, delegation is turned on, and all supported controllers are 1058 enabled for the unit, making them available to the unit's processes for management. If false, delegation is 1059 turned off entirely (and no additional controllers are enabled). If set to a list of controllers, delegation 1060 is turned on, and the specified controllers are enabled for the unit. Note that additional controllers than 1061 the ones specified might be made available as well, depending on configuration of the containing slice unit 1062 or other units contained in it. Note that assigning the empty string will enable delegation, but reset the 1063 list of controllers, all assignments prior to this will have no effect. Defaults to false.</para> 1064 1065 <para>Note that controller delegation to less privileged code is only safe on the unified control group 1066 hierarchy. Accordingly, access to the specified controllers will not be granted to unprivileged services on 1067 the legacy hierarchy, even when requested.</para> 1068 1069 <xi:include href="supported-controllers.xml" xpointer="controllers-text" /> 1070 1071 <para>Not all of these controllers are available on all kernels however, and some are 1072 specific to the unified hierarchy while others are specific to the legacy hierarchy. Also note that the 1073 kernel might support further controllers, which aren't covered here yet as delegation is either not supported 1074 at all for them or not defined cleanly.</para> 1075 1076 <para>For further details on the delegation model consult <ulink 1077 url="https://systemd.io/CGROUP_DELEGATION">Control Group APIs and Delegation</ulink>.</para> 1078 </listitem> 1079 </varlistentry> 1080 1081 <varlistentry> 1082 <term><varname>DisableControllers=</varname></term> 1083 1084 <listitem> 1085 <para>Disables controllers from being enabled for a unit's children. If a controller listed is already in use 1086 in its subtree, the controller will be removed from the subtree. This can be used to avoid child units being 1087 able to implicitly or explicitly enable a controller. Defaults to not disabling any controllers.</para> 1088 1089 <para>It may not be possible to successfully disable a controller if the unit or any child of the unit in 1090 question delegates controllers to its children, as any delegated subtree of the cgroup hierarchy is unmanaged 1091 by systemd.</para> 1092 1093 <para>Multiple controllers may be specified, separated by spaces. You may also pass 1094 <varname>DisableControllers=</varname> multiple times, in which case each new instance adds another controller 1095 to disable. Passing <varname>DisableControllers=</varname> by itself with no controller name present resets 1096 the disabled controller list.</para> 1097 1098 <xi:include href="supported-controllers.xml" xpointer="controllers-text" /> 1099 </listitem> 1100 </varlistentry> 1101 1102 <varlistentry> 1103 <term><varname>ManagedOOMSwap=auto|kill</varname></term> 1104 <term><varname>ManagedOOMMemoryPressure=auto|kill</varname></term> 1105 1106 <listitem> 1107 <para>Specifies how 1108 <citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> 1109 will act on this unit's cgroups. Defaults to <option>auto</option>.</para> 1110 1111 <para>When set to <option>kill</option>, the unit becomes a candidate for monitoring by 1112 <command>systemd-oomd</command>. If the cgroup passes the limits set by 1113 <citerefentry><refentrytitle>oomd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> or 1114 the unit configuration, <command>systemd-oomd</command> will select a descendant cgroup and send 1115 <constant>SIGKILL</constant> to all of the processes under it. You can find more details on 1116 candidates and kill behavior at 1117 <citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> 1118 and 1119 <citerefentry><refentrytitle>oomd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 1120 1121 <para>Setting either of these properties to <option>kill</option> will also result in 1122 <varname>After=</varname> and <varname>Wants=</varname> dependencies on 1123 <filename>systemd-oomd.service</filename> unless <varname>DefaultDependencies=no</varname>.</para> 1124 1125 <para>When set to <option>auto</option>, <command>systemd-oomd</command> will not actively use this 1126 cgroup's data for monitoring and detection. However, if an ancestor cgroup has one of these 1127 properties set to <option>kill</option>, a unit with <option>auto</option> can still be a candidate 1128 for <command>systemd-oomd</command> to terminate.</para> 1129 </listitem> 1130 </varlistentry> 1131 1132 <varlistentry> 1133 <term><varname>ManagedOOMMemoryPressureLimit=</varname></term> 1134 1135 <listitem> 1136 <para>Overrides the default memory pressure limit set by 1137 <citerefentry><refentrytitle>oomd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> for 1138 this unit (cgroup). Takes a percentage value between 0% and 100%, inclusive. This property is 1139 ignored unless <varname>ManagedOOMMemoryPressure=</varname><option>kill</option>. Defaults to 0%, 1140 which means to use the default set by 1141 <citerefentry><refentrytitle>oomd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. 1142 </para> 1143 </listitem> 1144 </varlistentry> 1145 1146 <varlistentry> 1147 <term><varname>ManagedOOMPreference=none|avoid|omit</varname></term> 1148 1149 <listitem> 1150 <para>Allows deprioritizing or omitting this unit's cgroup as a candidate when 1151 <command>systemd-oomd</command> needs to act. Requires support for extended attributes (see 1152 <citerefentry project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry>) 1153 in order to use <option>avoid</option> or <option>omit</option>. Additionally, 1154 <command>systemd-oomd</command> will ignore these extended attributes if the unit's cgroup is not 1155 owned by the root user.</para> 1156 1157 <para>If this property is set to <option>avoid</option>, the service manager will convey this to 1158 <command>systemd-oomd</command>, which will only select this cgroup if there are no other viable 1159 candidates.</para> 1160 1161 <para>If this property is set to <option>omit</option>, the service manager will convey this to 1162 <command>systemd-oomd</command>, which will ignore this cgroup as a candidate and will not perform 1163 any actions on it.</para> 1164 1165 <para>It is recommended to use <option>avoid</option> and <option>omit</option> sparingly, as it 1166 can adversely affect <command>systemd-oomd</command>'s kill behavior. Also note that these extended 1167 attributes are not applied recursively to cgroups under this unit's cgroup.</para> 1168 1169 <para>Defaults to <option>none</option> which means <command>systemd-oomd</command> will rank this 1170 unit's cgroup as defined in 1171 <citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> 1172 and <citerefentry><refentrytitle>oomd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. 1173 </para> 1174 </listitem> 1175 </varlistentry> 1176 </variablelist> 1177 </refsect1> 1178 1179 <refsect1> 1180 <title>Deprecated Options</title> 1181 1182 <para>The following options are deprecated. Use the indicated superseding options instead:</para> 1183 1184 <variablelist class='unit-directives'> 1185 1186 <varlistentry> 1187 <term><varname>CPUShares=<replaceable>weight</replaceable></varname></term> 1188 <term><varname>StartupCPUShares=<replaceable>weight</replaceable></varname></term> 1189 1190 <listitem> 1191 <para>Assign the specified CPU time share weight to the processes executed. These options take an integer 1192 value and control the <literal>cpu.shares</literal> control group attribute. The allowed range is 2 to 1193 262144. Defaults to 1024. For details about this control group attribute, see <ulink 1194 url="https://www.kernel.org/doc/html/latest/scheduler/sched-design-CFS.html">CFS Scheduler</ulink>. 1195 The available CPU time is split up among all units within one slice relative to their CPU time share 1196 weight.</para> 1197 1198 <para>While <varname>StartupCPUShares=</varname> applies to the startup and shutdown phases of the system, 1199 <varname>CPUShares=</varname> applies to normal runtime of the system, and if the former is not set also to 1200 the startup and shutdown phases. Using <varname>StartupCPUShares=</varname> allows prioritizing specific services at 1201 boot-up and shutdown differently than during normal runtime.</para> 1202 1203 <para>Implies <literal>CPUAccounting=yes</literal>.</para> 1204 1205 <para>These settings are deprecated. Use <varname>CPUWeight=</varname> and 1206 <varname>StartupCPUWeight=</varname> instead.</para> 1207 </listitem> 1208 </varlistentry> 1209 1210 <varlistentry> 1211 <term><varname>MemoryLimit=<replaceable>bytes</replaceable></varname></term> 1212 1213 <listitem> 1214 <para>Specify the limit on maximum memory usage of the executed processes. The limit specifies how much 1215 process and kernel memory can be used by tasks in this unit. Takes a memory size in bytes. If the value is 1216 suffixed with K, M, G or T, the specified memory size is parsed as Kilobytes, Megabytes, Gigabytes, or 1217 Terabytes (with the base 1024), respectively. Alternatively, a percentage value may be specified, which is 1218 taken relative to the installed physical memory on the system. If assigned the special value 1219 <literal>infinity</literal>, no memory limit is applied. This controls the 1220 <literal>memory.limit_in_bytes</literal> control group attribute. For details about this control group 1221 attribute, see <ulink 1222 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html">Memory Resource Controller</ulink>.</para> 1223 1224 <para>Implies <literal>MemoryAccounting=yes</literal>.</para> 1225 1226 <para>This setting is deprecated. Use <varname>MemoryMax=</varname> instead.</para> 1227 </listitem> 1228 </varlistentry> 1229 1230 <varlistentry> 1231 <term><varname>BlockIOAccounting=</varname></term> 1232 1233 <listitem> 1234 <para>Turn on Block I/O accounting for this unit, if the legacy control group hierarchy is used on the 1235 system. Takes a boolean argument. Note that turning on block I/O accounting for one unit will also implicitly 1236 turn it on for all units contained in the same slice and all for its parent slices and the units contained 1237 therein. The system default for this setting may be controlled with 1238 <varname>DefaultBlockIOAccounting=</varname> in 1239 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para> 1240 1241 <para>This setting is deprecated. Use <varname>IOAccounting=</varname> instead.</para> 1242 </listitem> 1243 </varlistentry> 1244 1245 <varlistentry> 1246 <term><varname>BlockIOWeight=<replaceable>weight</replaceable></varname></term> 1247 <term><varname>StartupBlockIOWeight=<replaceable>weight</replaceable></varname></term> 1248 1249 <listitem><para>Set the default overall block I/O weight for the executed processes, if the legacy control 1250 group hierarchy is used on the system. Takes a single weight value (between 10 and 1000) to set the default 1251 block I/O weight. This controls the <literal>blkio.weight</literal> control group attribute, which defaults to 1252 500. For details about this control group attribute, see <ulink 1253 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller</ulink>. 1254 The available I/O bandwidth is split up among all units within one slice relative to their block I/O 1255 weight.</para> 1256 1257 <para>While <varname>StartupBlockIOWeight=</varname> only 1258 applies to the startup and shutdown phases of the system, 1259 <varname>BlockIOWeight=</varname> applies to the later runtime 1260 of the system, and if the former is not set also to the 1261 startup and shutdown phases. This allows prioritizing specific services at 1262 boot-up and shutdown differently than during runtime.</para> 1263 1264 <para>Implies 1265 <literal>BlockIOAccounting=yes</literal>.</para> 1266 1267 <para>These settings are deprecated. Use <varname>IOWeight=</varname> and <varname>StartupIOWeight=</varname> 1268 instead.</para> 1269 1270 </listitem> 1271 </varlistentry> 1272 1273 <varlistentry> 1274 <term><varname>BlockIODeviceWeight=<replaceable>device</replaceable> <replaceable>weight</replaceable></varname></term> 1275 1276 <listitem> 1277 <para>Set the per-device overall block I/O weight for the executed processes, if the legacy control group 1278 hierarchy is used on the system. Takes a space-separated pair of a file path and a weight value to specify 1279 the device specific weight value, between 10 and 1000. (Example: "/dev/sda 500"). The file path may be 1280 specified as path to a block device node or as any other file, in which case the backing block device of the 1281 file system of the file is determined. This controls the <literal>blkio.weight_device</literal> control group 1282 attribute, which defaults to 1000. Use this option multiple times to set weights for multiple devices. For 1283 details about this control group attribute, see <ulink 1284 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller</ulink>.</para> 1285 1286 <para>Implies 1287 <literal>BlockIOAccounting=yes</literal>.</para> 1288 1289 <para>This setting is deprecated. Use <varname>IODeviceWeight=</varname> instead.</para> 1290 </listitem> 1291 </varlistentry> 1292 1293 <varlistentry> 1294 <term><varname>BlockIOReadBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term> 1295 <term><varname>BlockIOWriteBandwidth=<replaceable>device</replaceable> <replaceable>bytes</replaceable></varname></term> 1296 1297 <listitem> 1298 <para>Set the per-device overall block I/O bandwidth limit for the executed processes, if the legacy control 1299 group hierarchy is used on the system. Takes a space-separated pair of a file path and a bandwidth value (in 1300 bytes per second) to specify the device specific bandwidth. The file path may be a path to a block device 1301 node, or as any other file in which case the backing block device of the file system of the file is used. If 1302 the bandwidth is suffixed with K, M, G, or T, the specified bandwidth is parsed as Kilobytes, Megabytes, 1303 Gigabytes, or Terabytes, respectively, to the base of 1000. (Example: 1304 "/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This controls the 1305 <literal>blkio.throttle.read_bps_device</literal> and <literal>blkio.throttle.write_bps_device</literal> 1306 control group attributes. Use this option multiple times to set bandwidth limits for multiple devices. For 1307 details about these control group attributes, see <ulink 1308 url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/blkio-controller.html">Block IO Controller</ulink>. 1309 </para> 1310 1311 <para>Implies 1312 <literal>BlockIOAccounting=yes</literal>.</para> 1313 1314 <para>These settings are deprecated. Use <varname>IOReadBandwidthMax=</varname> and 1315 <varname>IOWriteBandwidthMax=</varname> instead.</para> 1316 </listitem> 1317 </varlistentry> 1318 1319 </variablelist> 1320 </refsect1> 1321 1322 <refsect1> 1323 <title>See Also</title> 1324 <para> 1325 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, 1326 <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1327 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1328 <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1329 <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1330 <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1331 <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1332 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1333 <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1334 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, 1335 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>, 1336 <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>, 1337 <citerefentry><refentrytitle>systemd-oomd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, 1338 The documentation for control groups and specific controllers in the Linux kernel: 1339 <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html">Control Groups v2</ulink>. 1340 </para> 1341 </refsect1> 1342</refentry> 1343