man/udevadm.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="udevadm"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>udevadm</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>udevadm</refentrytitle>
  16     <manvolnum>8</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>udevadm</refname><refpurpose>udev management tool</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <cmdsynopsis>
  25       <command>udevadm</command>
  26         <arg><option>--debug</option></arg>
  27         <arg><option>--version</option></arg>
  28         <arg><option>--help</option></arg>
  29     </cmdsynopsis>
  30     <cmdsynopsis>
  31       <command>udevadm info <optional>options</optional> <optional>devpath</optional></command>
  32     </cmdsynopsis>
  33     <cmdsynopsis>
  34       <command>udevadm trigger <optional>options</optional> <optional>devpath</optional></command>
  35     </cmdsynopsis>
  36     <cmdsynopsis>
  37       <command>udevadm settle <optional>options</optional></command>
  38     </cmdsynopsis>
  39     <cmdsynopsis>
  40       <command>udevadm control <replaceable>option</replaceable></command>
  41     </cmdsynopsis>
  42     <cmdsynopsis>
  43       <command>udevadm monitor <optional>options</optional></command>
  44     </cmdsynopsis>
  45     <cmdsynopsis>
  46       <command>udevadm test <optional>options</optional> <replaceable>devpath</replaceable></command>
  47     </cmdsynopsis>
  48     <cmdsynopsis>
  49       <command>udevadm test-builtin <optional>options</optional> <replaceable>command</replaceable> <replaceable>devpath</replaceable></command>
  50     </cmdsynopsis>
  51     <cmdsynopsis>
  52       <command>udevadm verify</command>
  53       <arg choice="opt" rep="repeat">options</arg>
  54       <arg choice="opt" rep="repeat"><replaceable>file</replaceable></arg>
  55     </cmdsynopsis>
  56     <cmdsynopsis>
  57       <command>udevadm wait <optional>options</optional> <replaceable>device|syspath</replaceable></command>
  58     </cmdsynopsis>
  59     <cmdsynopsis>
  60       <command>udevadm lock <optional>options</optional> <replaceable>command</replaceable></command>
  61     </cmdsynopsis>
  62   </refsynopsisdiv>
  63
  64   <refsect1><title>Description</title>
  65     <para><command>udevadm</command> expects a command and command
  66     specific options.  It controls the runtime behavior of
  67     <command>systemd-udevd</command>, requests kernel events, manages
  68     the event queue, and provides simple debugging mechanisms.</para>
  69   </refsect1>
  70
  71   <refsect1><title>Options</title>
  72     <variablelist>
  73       <varlistentry>
  74         <term><option>-d</option></term>
  75         <term><option>--debug</option></term>
  76         <listitem>
  77           <para>Print debug messages to standard error. This option is implied in <command>udevadm test</command> and
  78           <command>udevadm test-builtin</command> commands.</para>
  79         </listitem>
  80       </varlistentry>
  81
  82       <xi:include href="standard-options.xml" xpointer="help" />
  83     </variablelist>
  84
  85     <refsect2><title>udevadm info
  86       <optional><replaceable>options</replaceable></optional>
  87       <optional><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></optional>
  88     </title>
  89
  90       <para>Query the udev database for device information.</para>
  91
  92       <para>Positional arguments should be used to specify one or more devices. Each one may be a device name
  93       (in which case it must start with <filename>/dev/</filename>), a sys path (in which case it must start
  94       with <filename>/sys/</filename>), or a systemd device unit name (in which case it must end with
  95       <literal>.device</literal>, see
  96       <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
  97       </para>
  98
  99       <variablelist>
 100         <varlistentry>
 101           <term><option>-q</option></term>
 102           <term><option>--query=<replaceable>TYPE</replaceable></option></term>
 103           <listitem>
 104             <para>Query the database for the specified type of device data.
 105             Valid <replaceable>TYPE</replaceable>s are:
 106             <constant>name</constant>, <constant>symlink</constant>,
 107             <constant>path</constant>, <constant>property</constant>,
 108             <constant>all</constant>.</para>
 109           </listitem>
 110         </varlistentry>
 111
 112         <varlistentry>
 113           <term><option>--property=<replaceable>NAME</replaceable></option></term>
 114           <listitem>
 115             <para>When showing device properties using the <option>--query=property</option>
 116             option, limit display to properties specified in the argument. The argument should
 117             be a comma-separated list of property names. If not specified, all known properties
 118             are shown.</para>
 119
 120           <xi:include href="version-info.xml" xpointer="v250"/>
 121           </listitem>
 122         </varlistentry>
 123         <varlistentry>
 124           <term><option>--value</option></term>
 125           <listitem>
 126             <para>When showing device properties using the <option>--query=property</option>
 127             option, print only their values, and skip the property name and <literal>=</literal>.</para>
 128             <para>Cannot be used together with <option>-x/--export</option> or
 129             <option>-P/--export-prefix</option>.</para>
 130
 131             <xi:include href="version-info.xml" xpointer="v250"/>
 132           </listitem>
 133         </varlistentry>
 134         <varlistentry>
 135           <term><option>-p</option></term>
 136           <term><option>--path=<replaceable>DEVPATH</replaceable></option></term>
 137           <listitem>
 138             <para>The <filename>/sys/</filename> path of the device to query, e.g.
 139             <filename><optional>/sys/</optional>/class/block/sda</filename>. This option is an alternative to
 140             the positional argument with a <filename>/sys/</filename> prefix. <command>udevadm info
 141             --path=/class/block/sda</command> is equivalent to <command>udevadm info
 142             /sys/class/block/sda</command>.</para>
 143           </listitem>
 144         </varlistentry>
 145         <varlistentry>
 146           <term><option>-n</option></term>
 147           <term><option>--name=<replaceable>FILE</replaceable></option></term>
 148           <listitem>
 149             <para>The name of the device node or a symlink to query,
 150             e.g. <filename><optional>/dev/</optional>/sda</filename>. This option is an alternative to the
 151             positional argument with a <filename>/dev/</filename> prefix. <command>udevadm info
 152             --name=sda</command> is equivalent to <command>udevadm info /dev/sda</command>.</para>
 153           </listitem>
 154         </varlistentry>
 155         <varlistentry>
 156           <term><option>-r</option></term>
 157           <term><option>--root</option></term>
 158           <listitem>
 159             <para>Print absolute paths in <command>name</command> or <command>symlink</command>
 160             query.</para>
 161           </listitem>
 162         </varlistentry>
 163         <varlistentry>
 164           <term><option>-a</option></term>
 165           <term><option>--attribute-walk</option></term>
 166           <listitem>
 167             <para>Print all sysfs properties of the specified device that can be used
 168             in udev rules to match the specified device. It prints all devices
 169             along the chain, up to the root of sysfs that can be used in udev rules.</para>
 170           </listitem>
 171         </varlistentry>
 172         <varlistentry>
 173           <term><option>-t</option></term>
 174           <term><option>--tree</option></term>
 175           <listitem>
 176             <para>Display a sysfs tree. This recursively iterates through the sysfs hierarchy and displays it
 177             in a tree structure. If a path is specified only the subtree below and its parent directories are
 178             shown. This will show both device and subsystem items.</para>
 179
 180             <xi:include href="version-info.xml" xpointer="v251"/>
 181           </listitem>
 182         </varlistentry>
 183         <varlistentry>
 184           <term><option>-x</option></term>
 185           <term><option>--export</option></term>
 186           <listitem>
 187             <para>Print output as key/value pairs. Values are enclosed in single quotes.
 188             This takes effects only when <option>--query=property</option> or
 189             <option>--device-id-of-file=<replaceable>FILE</replaceable></option> is specified.</para>
 190           </listitem>
 191         </varlistentry>
 192         <varlistentry>
 193           <term><option>-P</option></term>
 194           <term><option>--export-prefix=<replaceable>NAME</replaceable></option></term>
 195           <listitem>
 196             <para>Add a prefix to the key name of exported values.
 197             This implies <option>--export</option>.</para>
 198           </listitem>
 199         </varlistentry>
 200         <varlistentry>
 201           <term><option>-d</option></term>
 202           <term><option>--device-id-of-file=<replaceable>FILE</replaceable></option></term>
 203           <listitem>
 204             <para>Print major/minor numbers of the underlying device, where the file lives on.
 205             If this is specified, all positional arguments are ignored.</para>
 206           </listitem>
 207         </varlistentry>
 208         <varlistentry>
 209           <term><option>-e</option></term>
 210           <term><option>--export-db</option></term>
 211           <listitem>
 212             <para>Export the content of the udev database.</para>
 213           </listitem>
 214         </varlistentry>
 215         <varlistentry>
 216           <term><option>-c</option></term>
 217           <term><option>--cleanup-db</option></term>
 218           <listitem>
 219             <para>Cleanup the udev database.</para>
 220           </listitem>
 221         </varlistentry>
 222         <varlistentry>
 223           <term><option>-w<optional>SECONDS</optional></option></term>
 224           <term><option>--wait-for-initialization<optional>=SECONDS</optional></option></term>
 225           <listitem>
 226             <para>Wait for device to be initialized. If argument <replaceable>SECONDS</replaceable>
 227             is not specified, the default is to wait forever.</para>
 228
 229           <xi:include href="version-info.xml" xpointer="v243"/>
 230           </listitem>
 231         </varlistentry>
 232         <varlistentry>
 233           <term><option>--subsystem-match<optional>=SUBSYSTEM</optional></option></term>
 234           <term><option>--subsystem-nomatch<optional>=SUBSYSTEM</optional></option></term>
 235           <listitem>
 236             <para>When used with <option>--export-db</option>, only show devices of or not of the given
 237             subsystem respectively.</para>
 238
 239           <xi:include href="version-info.xml" xpointer="v255"/>
 240           </listitem>
 241         </varlistentry>
 242         <varlistentry>
 243           <term><option>--attr-match<optional>=FILE[=VALUE]</optional></option></term>
 244           <term><option>--attr-nomatch<optional>=FILE[=VALUE]</optional></option></term>
 245           <listitem>
 246             <para>When used with <option>--export-db</option>, only show devices matching or not matching the
 247             given attribute respectively.</para>
 248
 249           <xi:include href="version-info.xml" xpointer="v255"/>
 250           </listitem>
 251         </varlistentry>
 252         <varlistentry>
 253           <term><option>--property-match<optional>=KEY=VALUE</optional></option></term>
 254           <listitem>
 255             <para>When used with <option>--export-db</option>, only show devices matching the given property
 256             and value.</para>
 257
 258           <xi:include href="version-info.xml" xpointer="v255"/>
 259           </listitem>
 260         </varlistentry>
 261         <varlistentry>
 262           <term><option>--tag-match<optional>=TAG</optional></option></term>
 263           <listitem>
 264             <para>When used with <option>--export-db</option>, only show devices with the given tag.</para>
 265
 266           <xi:include href="version-info.xml" xpointer="v255"/>
 267           </listitem>
 268         </varlistentry>
 269         <varlistentry>
 270           <term><option>--sysname-match<optional>=NAME</optional></option></term>
 271           <listitem>
 272             <para>When used with <option>--export-db</option>, only show devices with the given
 273             <literal>/sys</literal> path.</para>
 274
 275           <xi:include href="version-info.xml" xpointer="v255"/>
 276           </listitem>
 277         </varlistentry>
 278         <varlistentry>
 279           <term><option>--name-match<optional>=NAME</optional></option></term>
 280           <listitem>
 281             <para>When used with <option>--export-db</option>, only show devices with the given name in
 282             <literal>/dev</literal>.</para>
 283
 284           <xi:include href="version-info.xml" xpointer="v255"/>
 285           </listitem>
 286         </varlistentry>
 287         <varlistentry>
 288           <term><option>--parent-match<optional>=NAME</optional></option></term>
 289           <listitem>
 290             <para>When used with <option>--export-db</option>, only show devices with the given parent
 291             device.</para>
 292
 293           <xi:include href="version-info.xml" xpointer="v255"/>
 294           </listitem>
 295         </varlistentry>
 296         <varlistentry>
 297           <term><option>--initialized-match</option></term>
 298           <term><option>--initialized-nomatch</option></term>
 299           <listitem>
 300             <para>When used with <option>--export-db</option>, only show devices that are initialized or not
 301             initialized respectively.</para>
 302
 303           <xi:include href="version-info.xml" xpointer="v255"/>
 304           </listitem>
 305         </varlistentry>
 306
 307         <xi:include href="standard-options.xml" xpointer="json" />
 308         <xi:include href="standard-options.xml" xpointer="help" />
 309         <xi:include href="standard-options.xml" xpointer="no-pager" />
 310       </variablelist>
 311
 312       <para>The generated output shows the current device database entry in a terse format. Each line shown
 313       is prefixed with one of the following characters:</para>
 314
 315       <table>
 316         <title><command>udevadm info</command> output prefixes</title>
 317         <tgroup cols='2' align='left' colsep='1' rowsep='1'>
 318           <colspec colname="prefix" />
 319           <colspec colname="meaning" />
 320           <thead>
 321             <row>
 322               <entry>Prefix</entry>
 323               <entry>Meaning</entry>
 324             </row>
 325           </thead>
 326           <tbody>
 327             <row>
 328               <entry><literal>P:</literal></entry>
 329               <entry>Device path in <filename>/sys/</filename></entry>
 330             </row>
 331             <row>
 332               <entry><literal>M:</literal></entry>
 333               <entry>Device name in <filename>/sys/</filename> (i.e. the last component of <literal>P:</literal>)</entry>
 334             </row>
 335             <row>
 336               <entry><literal>R:</literal></entry>
 337               <entry>Device number in <filename>/sys/</filename> (i.e. the numeric suffix of the last component of <literal>P:</literal>)</entry>
 338             </row>
 339             <row>
 340               <entry><literal>U:</literal></entry>
 341               <entry>Kernel subsystem</entry>
 342             </row>
 343             <row>
 344               <entry><literal>T:</literal></entry>
 345               <entry>Kernel device type within subsystem</entry>
 346             </row>
 347             <row>
 348               <entry><literal>D:</literal></entry>
 349               <entry>Kernel device node major/minor</entry>
 350             </row>
 351             <row>
 352               <entry><literal>I:</literal></entry>
 353               <entry>Network interface index</entry>
 354             </row>
 355             <row>
 356               <entry><literal>N:</literal></entry>
 357               <entry>Kernel device node name</entry>
 358             </row>
 359             <row>
 360               <entry><literal>L:</literal></entry>
 361               <entry>Device node symlink priority</entry>
 362             </row>
 363             <row>
 364               <entry><literal>S:</literal></entry>
 365               <entry>Device node symlink</entry>
 366             </row>
 367             <row>
 368               <entry><literal>Q:</literal></entry>
 369               <entry>Block device sequence number (DISKSEQ)</entry>
 370             </row>
 371             <row>
 372               <entry><literal>V:</literal></entry>
 373               <entry>Attached driver</entry>
 374             </row>
 375             <row>
 376               <entry><literal>E:</literal></entry>
 377               <entry>Device property</entry>
 378             </row>
 379           </tbody>
 380         </tgroup>
 381       </table>
 382     </refsect2>
 383
 384     <refsect2><title>udevadm trigger
 385       <optional><replaceable>options</replaceable></optional>
 386       <optional><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></optional>
 387       </title>
 388       <para>Request device events from the kernel. Primarily used to replay events at system coldplug time.</para>
 389
 390       <para>Takes device specifications as positional arguments. See the description of <command>info</command>
 391       above.</para>
 392
 393       <variablelist>
 394         <varlistentry>
 395           <term><option>-v</option></term>
 396           <term><option>--verbose</option></term>
 397           <listitem>
 398             <para>Print the list of devices which will be triggered.</para>
 399           </listitem>
 400         </varlistentry>
 401         <varlistentry>
 402           <term><option>-n</option></term>
 403           <term><option>--dry-run</option></term>
 404           <listitem>
 405             <para>Do not actually trigger the event.</para>
 406           </listitem>
 407         </varlistentry>
 408         <varlistentry>
 409           <term><option>-q</option></term>
 410           <term><option>--quiet</option></term>
 411           <listitem>
 412             <para>Suppress error logging in triggering events.</para>
 413
 414           <xi:include href="version-info.xml" xpointer="v248"/>
 415           </listitem>
 416         </varlistentry>
 417         <varlistentry>
 418           <term><option>-t</option></term>
 419           <term><option>--type=<replaceable>TYPE</replaceable></option></term>
 420           <listitem>
 421             <para>Trigger a specific type of devices. Valid types are <literal>all</literal>,
 422             <literal>devices</literal>, and <literal>subsystems</literal>. The default value is
 423             <literal>devices</literal>.</para>
 424           </listitem>
 425         </varlistentry>
 426         <varlistentry>
 427           <term><option>-c</option></term>
 428           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 429           <listitem>
 430             <para>Type of event to be triggered. Possible actions are <literal>add</literal>,
 431             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 432             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 433             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 434             to list the possible actions. The default value is <literal>change</literal>.
 435             </para>
 436           </listitem>
 437         </varlistentry>
 438         <varlistentry>
 439           <term><option>--prioritized-subsystem=<replaceable>SUBSYSTEM<optional>,<replaceable>SUBSYSTEM</replaceable>…</optional></replaceable></option></term>
 440           <listitem>
 441             <para>Takes a comma separated list of subsystems. When triggering events for devices, the
 442             devices from the specified subsystems and their parents are triggered first. For example,
 443             if <option>--prioritized-subsystem=block,net</option>, then firstly all block devices and
 444             their parents are triggered, in the next all network devices and their parents are
 445             triggered, and lastly the other devices are triggered. This option can be specified
 446             multiple times, and in that case the lists of the subsystems will be merged. That is,
 447             <option>--prioritized-subsystem=block --prioritized-subsystem=net</option> is equivalent to
 448             <option>--prioritized-subsystem=block,net</option>.</para>
 449
 450             <xi:include href="version-info.xml" xpointer="v251"/>
 451           </listitem>
 452         </varlistentry>
 453         <varlistentry>
 454           <term><option>-s</option></term>
 455           <term><option>--subsystem-match=<replaceable>SUBSYSTEM</replaceable></option></term>
 456           <listitem>
 457             <para>Trigger events for devices which belong to a
 458             matching subsystem. This option supports shell style pattern matching.
 459             When this option is specified more than once, then each matching result is ORed, that is,
 460             all the devices in each subsystem are triggered.</para>
 461           </listitem>
 462         </varlistentry>
 463         <varlistentry>
 464           <term><option>-S</option></term>
 465           <term><option>--subsystem-nomatch=<replaceable>SUBSYSTEM</replaceable></option></term>
 466           <listitem>
 467             <para>Do not trigger events for devices which belong to a matching subsystem. This option
 468             supports shell style pattern matching. When this option is specified more than once,
 469             then each matching result is ANDed, that is, devices which do not match all specified
 470             subsystems are triggered.</para>
 471           </listitem>
 472         </varlistentry>
 473         <varlistentry>
 474           <term><option>-a</option></term>
 475           <term><option>--attr-match=<replaceable>ATTRIBUTE</replaceable>=<replaceable>VALUE</replaceable></option></term>
 476           <listitem>
 477             <para>Trigger events for devices with a matching sysfs attribute. If a value is specified along
 478             with the attribute name, the content of the attribute is matched against the given value using
 479             shell style pattern matching. If no value is specified, the existence of the sysfs attribute is
 480             checked. When this option is specified multiple times, then each matching result is ANDed,
 481             that is, only devices which have all specified attributes are triggered.</para>
 482           </listitem>
 483         </varlistentry>
 484         <varlistentry>
 485           <term><option>-A</option></term>
 486           <term><option>--attr-nomatch=<replaceable>ATTRIBUTE</replaceable>=<replaceable>VALUE</replaceable></option></term>
 487           <listitem>
 488             <para>Do not trigger events for devices with a matching sysfs attribute. If a value is specified
 489             along with the attribute name, the content of the attribute is matched against the given value
 490             using shell style pattern matching. If no value is specified, the existence of the sysfs attribute
 491             is checked. When this option is specified multiple times, then each matching result is ANDed,
 492             that is, only devices which have none of the specified attributes are triggered.</para>
 493           </listitem>
 494         </varlistentry>
 495         <varlistentry>
 496           <term><option>-p</option></term>
 497           <term><option>--property-match=<replaceable>PROPERTY</replaceable>=<replaceable>VALUE</replaceable></option></term>
 498           <listitem>
 499             <para>Trigger events for devices with a matching property value. This option supports shell style
 500             pattern matching. When this option is specified more than once, then each matching result is ORed,
 501             that is, devices which have one of the specified properties are triggered.</para>
 502           </listitem>
 503         </varlistentry>
 504         <varlistentry>
 505           <term><option>-g</option></term>
 506           <term><option>--tag-match=<replaceable>TAG</replaceable></option></term>
 507           <listitem>
 508             <para>Trigger events for devices with a matching tag. When this option is specified multiple times,
 509             then each matching result is ANDed, that is, devices which have all specified tags are triggered.</para>
 510           </listitem>
 511         </varlistentry>
 512         <varlistentry>
 513           <term><option>-y</option></term>
 514           <term><option>--sysname-match=<replaceable>NAME</replaceable></option></term>
 515           <listitem>
 516             <para>Trigger events for devices for which the last component (i.e. the filename) of the
 517             <filename>/sys/</filename> path matches the specified <replaceable>PATH</replaceable>. This option
 518             supports shell style pattern matching. When this option is specified more than once, then each
 519             matching result is ORed, that is, all devices which have any of the specified
 520             <replaceable>NAME</replaceable> are triggered.</para>
 521           </listitem>
 522         </varlistentry>
 523         <varlistentry>
 524           <term><option>--name-match=<replaceable>NAME</replaceable></option></term>
 525           <listitem>
 526             <para>Trigger events for devices with a matching device path. When this option is specified more than once,
 527             then each matching result is ORed, that is, all specified devices are triggered.</para>
 528
 529             <xi:include href="version-info.xml" xpointer="v218"/>
 530           </listitem>
 531         </varlistentry>
 532         <varlistentry>
 533           <term><option>-b</option></term>
 534           <term><option>--parent-match=<replaceable>SYSPATH</replaceable></option></term>
 535           <listitem>
 536             <para>Trigger events for all children of a given device. When this option is specified more than once,
 537             then each matching result is ORed, that is, all children of each specified device are triggered.</para>
 538           </listitem>
 539         </varlistentry>
 540         <varlistentry>
 541           <term><option>--initialized-match</option></term>
 542           <term><option>--initialized-nomatch</option></term>
 543           <listitem>
 544             <para>When <option>--initialized-match</option> is specified, trigger events for devices
 545             that are already initialized by <command>systemd-udevd</command>, and skip devices that
 546             are not initialized yet.</para>
 547             <para>When <option>--initialized-nomatch</option> is specified, trigger events for devices
 548             that are not initialized by <command>systemd-udevd</command> yet, and skip devices that
 549             are already initialized.</para>
 550             <para>Typically, it is essential that applications which intend to use such a match, make
 551             sure a suitable udev rule is installed that sets at least one property on devices that
 552             shall be matched. See also Initialized Devices section below for more details.</para>
 553             <warning>
 554               <para><option>--initialized-nomatch</option> can potentially save a significant
 555               amount of time compared to re-triggering all devices in the system and e.g. can be used to
 556               optimize boot time. However, this is not safe to be used in a boot sequence in general.
 557               Especially, when udev rules for a device depend on its parent devices (e.g.
 558               <literal>ATTRS</literal> or <literal>IMPORT{parent}</literal> keys, see
 559               <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 560               for more details), the final state of the device becomes easily unstable with this option.
 561               </para>
 562             </warning>
 563
 564             <xi:include href="version-info.xml" xpointer="v251"/>
 565           </listitem>
 566         </varlistentry>
 567         <varlistentry>
 568           <term><option>-w</option></term>
 569           <term><option>--settle</option></term>
 570           <listitem>
 571             <para>Apart from triggering events, also waits for those events to
 572             finish. Note that this is different from calling <command>udevadm
 573             settle</command>. <command>udevadm settle</command> waits for all
 574             events to finish. This option only waits for events triggered by
 575             the same command to finish.</para>
 576
 577             <xi:include href="version-info.xml" xpointer="v238"/>
 578           </listitem>
 579         </varlistentry>
 580         <varlistentry>
 581           <term><option>--uuid</option></term>
 582           <listitem>
 583             <para>Trigger the synthetic device events, and associate a randomized UUID with each. These UUIDs
 584             are printed to standard output, one line for each event. These UUIDs are included in the uevent
 585             environment block (in the <literal>SYNTH_UUID=</literal> property) and may be used to track
 586             delivery of the generated events.</para>
 587
 588             <xi:include href="version-info.xml" xpointer="v249"/>
 589           </listitem>
 590         </varlistentry>
 591         <varlistentry>
 592           <term><option>--wait-daemon[=<replaceable>SECONDS</replaceable>]</option></term>
 593           <listitem>
 594             <para>Before triggering uevents, wait for systemd-udevd daemon to be initialized.
 595             Optionally takes timeout value. Default timeout is 5 seconds. This is equivalent to invoking
 596             <command>udevadm control --ping</command> before <command>udevadm trigger</command>.</para>
 597
 598             <xi:include href="version-info.xml" xpointer="v241"/>
 599           </listitem>
 600         </varlistentry>
 601
 602         <xi:include href="standard-options.xml" xpointer="help" />
 603       </variablelist>
 604
 605       <para>In addition, optional positional arguments can be used
 606       to specify device names or sys paths. They must start with
 607       <filename>/dev/</filename> or <filename>/sys/</filename>
 608       respectively.</para>
 609     </refsect2>
 610
 611     <refsect2><title>udevadm settle
 612       <optional><replaceable>options</replaceable></optional>
 613     </title>
 614       <para>Watches the udev event queue, and exits if all current events are handled.</para>
 615       <variablelist>
 616         <varlistentry>
 617           <term><option>-t</option></term>
 618           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 619           <listitem>
 620             <para>Maximum number of seconds to wait for the event
 621             queue to become empty. The default value is 120 seconds. A
 622             value of 0 will check if the queue is empty and always
 623             return immediately. A non-zero value will return an exit
 624             code of 0 if queue became empty before timeout was reached,
 625             non-zero otherwise.</para>
 626           </listitem>
 627         </varlistentry>
 628         <varlistentry>
 629           <term><option>-E</option></term>
 630           <term><option>--exit-if-exists=<replaceable>FILE</replaceable></option></term>
 631           <listitem>
 632             <para>Stop waiting if file exists.</para>
 633           </listitem>
 634         </varlistentry>
 635
 636         <xi:include href="standard-options.xml" xpointer="help" />
 637       </variablelist>
 638
 639       <para>See
 640       <citerefentry><refentrytitle>systemd-udev-settle.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 641       for more information.</para>
 642     </refsect2>
 643
 644     <refsect2><title>udevadm control <replaceable>option</replaceable></title>
 645       <para>Modify the internal state of the running udev daemon.</para>
 646       <variablelist>
 647         <varlistentry>
 648           <term><option>-e</option></term>
 649           <term><option>--exit</option></term>
 650           <listitem>
 651             <para>Signal and wait for systemd-udevd to exit. No option except for
 652             <option>--timeout</option> can be specified after this option.
 653             Note that <filename>systemd-udevd.service</filename> contains
 654             <option>Restart=always</option> and so as a result, this option restarts systemd-udevd.
 655             If you want to stop <filename>systemd-udevd.service</filename>, please use the following:
 656             <programlisting>systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd.service</programlisting>
 657             </para>
 658           </listitem>
 659         </varlistentry>
 660         <varlistentry>
 661           <term><option>-l</option></term>
 662           <term><option>--log-level=<replaceable>value</replaceable></option></term>
 663           <listitem>
 664             <para>Set the internal log level of
 665             <filename>systemd-udevd</filename>. Valid values are the
 666             numerical syslog priorities or their textual
 667             representations: <option>emerg</option>,
 668             <option>alert</option>, <option>crit</option>,
 669             <option>err</option>, <option>warning</option>,
 670             <option>notice</option>, <option>info</option>, and
 671             <option>debug</option>.</para>
 672           </listitem>
 673         </varlistentry>
 674         <varlistentry>
 675           <term><option>-s</option></term>
 676           <term><option>--stop-exec-queue</option></term>
 677           <listitem>
 678             <para>Signal systemd-udevd to stop executing new events. Incoming events
 679             will be queued.</para>
 680           </listitem>
 681         </varlistentry>
 682         <varlistentry>
 683           <term><option>-S</option></term>
 684           <term><option>--start-exec-queue</option></term>
 685           <listitem>
 686             <para>Signal systemd-udevd to enable the execution of events.</para>
 687           </listitem>
 688         </varlistentry>
 689         <varlistentry>
 690           <term><option>-R</option></term>
 691           <term><option>--reload</option></term>
 692           <listitem>
 693             <para>Signal systemd-udevd to reload the rules files and other databases like the kernel
 694             module index. Reloading rules and databases does not apply any changes to already
 695             existing devices; the new configuration will only be applied to new events.</para>
 696           </listitem>
 697         </varlistentry>
 698         <varlistentry>
 699           <term><option>-p</option></term>
 700           <term><option>--property=<replaceable>KEY</replaceable>=<replaceable>value</replaceable></option></term>
 701           <listitem>
 702             <para>Set a global property for all events.</para>
 703           </listitem>
 704         </varlistentry>
 705         <varlistentry>
 706           <term><option>-m</option></term>
 707           <term><option>--children-max=<replaceable>value</replaceable></option></term>
 708           <listitem>
 709             <para>Set the maximum number of events, systemd-udevd will handle at the same time. When 0 is
 710             specified, then the maximum is determined based on the system resources.</para>
 711           </listitem>
 712         </varlistentry>
 713         <varlistentry>
 714           <term><option>--ping</option></term>
 715           <listitem>
 716             <para>Send a ping message to systemd-udevd and wait for the reply. This may be useful to check that
 717             systemd-udevd daemon is running.</para>
 718
 719             <xi:include href="version-info.xml" xpointer="v241"/>
 720           </listitem>
 721         </varlistentry>
 722         <varlistentry>
 723           <term><option>-t</option></term>
 724           <term><option>--timeout=<replaceable>seconds</replaceable></option></term>
 725           <listitem>
 726             <para>The maximum number of seconds to wait for a reply from systemd-udevd.</para>
 727           </listitem>
 728         </varlistentry>
 729
 730         <xi:include href="standard-options.xml" xpointer="help" />
 731       </variablelist>
 732     </refsect2>
 733
 734     <refsect2><title>udevadm monitor
 735       <optional><replaceable>options</replaceable></optional>
 736     </title>
 737       <para>Listens to the kernel uevents and events sent out by a udev rule
 738       and prints the devpath of the event to the console. It can be used to analyze the
 739       event timing, by comparing the timestamps of the kernel uevent and the udev event.
 740       </para>
 741       <variablelist>
 742         <varlistentry>
 743           <term><option>-k</option></term>
 744           <term><option>--kernel</option></term>
 745           <listitem>
 746             <para>Print the kernel uevents.</para>
 747           </listitem>
 748         </varlistentry>
 749         <varlistentry>
 750           <term><option>-u</option></term>
 751           <term><option>--udev</option></term>
 752           <listitem>
 753             <para>Print the udev event after the rule processing.</para>
 754           </listitem>
 755         </varlistentry>
 756         <varlistentry>
 757           <term><option>-p</option></term>
 758           <term><option>--property</option></term>
 759           <listitem>
 760             <para>Also print the properties of the event.</para>
 761           </listitem>
 762         </varlistentry>
 763         <varlistentry>
 764           <term><option>-s</option></term>
 765           <term><option>--subsystem-match=<replaceable>string[/string]</replaceable></option></term>
 766           <listitem>
 767             <para>Filter kernel uevents and udev events by subsystem[/devtype]. Only events with a matching subsystem value will pass.
 768             When this option is specified more than once, then each matching result is ORed, that is, all devices in the specified
 769             subsystems are monitored.</para>
 770           </listitem>
 771         </varlistentry>
 772         <varlistentry>
 773           <term><option>-t</option></term>
 774           <term><option>--tag-match=<replaceable>string</replaceable></option></term>
 775           <listitem>
 776             <para>Filter udev events by tag. Only udev events with a given tag attached will pass.
 777             When this option is specified more than once, then each matching result is ORed, that is, devices which have one of the
 778             specified tags are monitored.</para>
 779           </listitem>
 780         </varlistentry>
 781
 782         <xi:include href="standard-options.xml" xpointer="help" />
 783       </variablelist>
 784     </refsect2>
 785
 786     <refsect2><title>udevadm test
 787       <optional><replaceable>options</replaceable></optional>
 788       <optional><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></optional>
 789     </title>
 790       <para>Simulate a udev event run for the given device, and print debug output.</para>
 791       <variablelist>
 792         <varlistentry>
 793           <term><option>-a</option></term>
 794           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 795           <listitem>
 796             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 797             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 798             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 799             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 800             to list the possible actions. The default value is <literal>add</literal>.</para>
 801           </listitem>
 802         </varlistentry>
 803         <varlistentry>
 804           <term><option>-N</option></term>
 805           <term><option>--resolve-names=<constant>early</constant>|<constant>late</constant>|<constant>never</constant></option></term>
 806           <listitem>
 807             <para>Specify when udevadm should resolve names of users
 808             and groups.  When set to <constant>early</constant> (the
 809             default), names will be resolved when the rules are
 810             parsed. When set to <constant>late</constant>, names will
 811             be resolved for every event. When set to
 812             <constant>never</constant>, names will never be resolved
 813             and all devices will be owned by root.</para>
 814
 815             <xi:include href="version-info.xml" xpointer="v209"/>
 816           </listitem>
 817         </varlistentry>
 818
 819         <xi:include href="standard-options.xml" xpointer="help" />
 820       </variablelist>
 821     </refsect2>
 822
 823     <refsect2><title>udevadm test-builtin
 824       <optional><replaceable>options</replaceable></optional>
 825       <replaceable>command</replaceable>
 826       <optional><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></optional>
 827     </title>
 828       <para>Run a built-in command <replaceable>COMMAND</replaceable>
 829       for device <replaceable>DEVPATH</replaceable>, and print debug
 830       output.</para>
 831       <variablelist>
 832         <varlistentry>
 833           <term><option>-a</option></term>
 834           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 835           <listitem>
 836             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 837             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 838             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 839             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 840             to list the possible actions. The default value is <literal>add</literal>.</para>
 841
 842           <xi:include href="version-info.xml" xpointer="v250"/>
 843           </listitem>
 844         </varlistentry>
 845
 846         <xi:include href="standard-options.xml" xpointer="help" />
 847         <xi:include href="standard-options.xml" xpointer="version" />
 848       </variablelist>
 849     </refsect2>
 850
 851     <refsect2>
 852       <title>udevadm verify
 853       <optional><replaceable>options</replaceable></optional>
 854       <optional><replaceable>file</replaceable></optional>
 855       …
 856       </title>
 857
 858       <para>Verify syntactic, semantic, and stylistic correctness of udev rules files.</para>
 859
 860       <para>Positional arguments could be used to specify one or more files to check.
 861       If no files are specified, the udev rules are read from the files located in
 862       the same udev/rules.d directories that are processed by the udev daemon.</para>
 863
 864       <para>The exit status is <constant>0</constant> if all specified udev
 865       rules files are syntactically, semantically, and stylistically correct,
 866       and a non-zero error code otherwise.</para>
 867
 868       <variablelist>
 869         <varlistentry>
 870           <term><option>-N</option></term>
 871           <term><option>--resolve-names=<constant>early</constant>|<constant>never</constant></option></term>
 872           <listitem>
 873             <para>Specify when udevadm should resolve names of users
 874             and groups.  When set to <constant>early</constant> (the
 875             default), names will be resolved when the rules are
 876             parsed. When set to <constant>never</constant>, names will
 877             never be resolved.</para>
 878
 879             <xi:include href="version-info.xml" xpointer="v254"/>
 880           </listitem>
 881         </varlistentry>
 882
 883         <varlistentry>
 884           <term><option>--root=<replaceable>PATH</replaceable></option></term>
 885           <listitem>
 886             <para>When looking for udev rules files located in udev/rules.d directories,
 887             operate on files underneath the specified root path <replaceable>PATH</replaceable>.</para>
 888
 889             <xi:include href="version-info.xml" xpointer="v254"/>
 890           </listitem>
 891         </varlistentry>
 892
 893         <varlistentry>
 894           <term><option>--no-summary</option></term>
 895           <listitem>
 896             <para>Do not show summary.</para>
 897
 898           <xi:include href="version-info.xml" xpointer="v254"/>
 899           </listitem>
 900         </varlistentry>
 901
 902         <varlistentry>
 903           <term><option>--no-style</option></term>
 904           <listitem>
 905             <para>Ignore style issues. When specified, even if style issues are found in udev rules files,
 906             the exit status is <constant>0</constant> if no syntactic or semantic errors are found.</para>
 907
 908             <xi:include href="version-info.xml" xpointer="v254"/>
 909           </listitem>
 910         </varlistentry>
 911
 912         <xi:include href="standard-options.xml" xpointer="help" />
 913       </variablelist>
 914     </refsect2>
 915
 916     <refsect2>
 917       <title>udevadm wait
 918       <optional><replaceable>options</replaceable></optional>
 919       <optional><replaceable>device|syspath</replaceable></optional>
 920       …
 921       </title>
 922
 923       <para>Wait for devices or device symlinks being created and initialized by
 924       <command>systemd-udevd</command>. Each device path must start with
 925       <literal>/dev/</literal> or <literal>/sys/</literal>, e.g. <literal>/dev/sda</literal>,
 926       <literal>/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1</literal>,
 927       <literal>/sys/devices/pci0000:00/0000:00:1f.6/net/eth0</literal>, or
 928       <literal>/sys/class/net/eth0</literal>. This can take multiple devices. This may be useful for
 929       waiting for devices being processed by <command>systemd-udevd</command> after e.g. partitioning
 930       or formatting the devices.</para>
 931
 932       <variablelist>
 933         <varlistentry>
 934           <term><option>-t</option></term>
 935           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 936           <listitem>
 937             <para>Maximum number of seconds to wait for the specified devices or device symlinks being
 938             created, initialized, or removed. The default value is <literal>infinity</literal>.</para>
 939
 940             <xi:include href="version-info.xml" xpointer="v251"/>
 941           </listitem>
 942         </varlistentry>
 943
 944         <varlistentry>
 945           <term><option>--initialized=<replaceable>BOOL</replaceable></option></term>
 946           <listitem>
 947             <para>Check if <command>systemd-udevd</command> initialized devices. Defaults to true. When
 948             false, the command only checks if the specified devices exist. Set false to this setting if
 949             there is no udev rules for the specified devices, as the devices will never be considered
 950             as initialized in that case. See Initialized Devices section below for more details.</para>
 951
 952           <xi:include href="version-info.xml" xpointer="v251"/>
 953           </listitem>
 954         </varlistentry>
 955
 956         <varlistentry>
 957           <term><option>--removed</option></term>
 958           <listitem>
 959             <para>When specified, the command wait for devices being removed instead of created or
 960             initialized. If this is specified, <option>--initialized=</option> will be ignored.</para>
 961
 962             <xi:include href="version-info.xml" xpointer="v251"/>
 963           </listitem>
 964         </varlistentry>
 965
 966         <varlistentry>
 967           <term><option>--settle</option></term>
 968           <listitem>
 969             <para>When specified, also watches the udev event queue, and wait for all queued events
 970             being processed by <command>systemd-udevd</command>.</para>
 971
 972             <xi:include href="version-info.xml" xpointer="v251"/>
 973           </listitem>
 974         </varlistentry>
 975
 976         <xi:include href="standard-options.xml" xpointer="help" />
 977       </variablelist>
 978     </refsect2>
 979
 980     <refsect2>
 981       <title>udevadm lock
 982       <optional><replaceable>options</replaceable></optional>
 983       <optional><replaceable>command</replaceable></optional>
 984       …
 985       </title>
 986
 987       <para><command>udevadm lock</command> takes an (advisory) exclusive lock on a block device (or all
 988       specified devices), as per <ulink url="https://systemd.io/BLOCK_DEVICE_LOCKING">Locking Block Device
 989       Access</ulink> and invokes a program with the locks taken. When the invoked program exits the locks
 990       are automatically released and its return value is propagated as exit code of <command>udevadm
 991       lock</command>.</para>
 992
 993       <para>This tool is in particular useful to ensure that
 994       <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 995       does not probe a block device while changes are made to it, for example partitions created or file
 996       systems formatted. Note that many tools that interface with block devices natively support taking
 997       relevant locks, see for example
 998       <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
 999       <option>--lock</option> switch.</para>
1000
1001       <para>The command expects at least one block device specified via <option>--device=</option> or
1002       <option>--backing=</option>, and a command line to execute as arguments.</para>
1003
1004       <variablelist>
1005         <varlistentry>
1006           <term><option>--device=<replaceable>DEVICE</replaceable></option></term>
1007           <term><option>-d <replaceable>DEVICE</replaceable></option></term>
1008
1009           <listitem><para>Takes a path to a device node of the device to lock. This switch may be used
1010           multiple times (and in combination with <option>--backing=</option>) in order to lock multiple
1011           devices. If a partition block device node is specified the containing "whole" block device is
1012           automatically determined and used for the lock, as per the specification. If multiple devices are
1013           specified, they are deduplicated, sorted by the major/minor of their device nodes and then locked
1014           in order.</para>
1015
1016           <para>This switch must be used at least once, to specify at least one device to
1017           lock. (Alternatively, use <option>--backing=</option>, see below.)</para>
1018
1019           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
1020         </varlistentry>
1021
1022         <varlistentry>
1023           <term><option>--backing=<replaceable>PATH</replaceable></option></term>
1024           <term><option>-b <replaceable>PATH</replaceable></option></term>
1025
1026           <listitem><para>If a path to a device node is specified, identical to
1027           <option>--device=</option>. However, this switch alternatively accepts a path to a regular file or
1028           directory, in which case the block device of the file system the file/directory resides on is
1029           automatically determined and used as if it was specified with
1030           <option>--device=</option>.</para>
1031
1032           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
1033         </varlistentry>
1034
1035         <varlistentry>
1036           <term><option>--timeout=<replaceable>SECS</replaceable></option></term>
1037           <term><option>-t <replaceable>SECS</replaceable></option></term>
1038
1039           <listitem><para>Specifies how long to wait at most until all locks can be taken. Takes a value in
1040           seconds, or in the usual supported time units, see
1041           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>. If
1042           specified as zero the lock is attempted and if not successful the invocation will immediately
1043           fail. If passed as <literal>infinity</literal> (the default) the invocation will wait indefinitely
1044           until the lock can be acquired. If the lock cannot be taken in the specified time the specified
1045           command will not be executed and the invocation will fail.</para>
1046
1047           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
1048         </varlistentry>
1049
1050         <varlistentry>
1051           <term><option>--print</option></term>
1052           <term><option>-p</option></term>
1053
1054           <listitem><para>Instead of locking the specified devices and executing a command, just print the
1055           device paths that would be locked, and execute no command. This command is useful to determine
1056           the "whole" block device in case a partition block device is specified. The devices will be sorted
1057           by their device node major number as primary ordering key and the minor number as secondary
1058           ordering key (i.e. they are shown in the order they'd be locked). Note that the number of lines
1059           printed here can be less than the number of <option>--device=</option> and
1060           <option>--backing=</option> switches specified in case these resolve to the same "whole"
1061           devices.</para>
1062
1063           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
1064         </varlistentry>
1065
1066         <xi:include href="standard-options.xml" xpointer="help" />
1067       </variablelist>
1068     </refsect2>
1069   </refsect1>
1070
1071   <refsect1>
1072     <title>Initialized Devices</title>
1073
1074     <para>Initialized devices are those for which at least one udev rule already completed execution
1075     – for any action but <literal>remove</literal> — that set a property or other device setting (and
1076     thus has an entry in the udev device database). Devices are no longer considered initialized if a
1077     <literal>remove</literal> action is seen for them (which removes their entry in the udev device
1078     database). Note that devices that have no udev rules are never considered initialized, but might
1079     still be announced via the sd-device API (or similar).</para>
1080   </refsect1>
1081
1082   <refsect1>
1083     <title>Example</title>
1084
1085     <example>
1086       <title>Format a File System</title>
1087
1088       <para>Take a lock on the backing block device while creating a file system, to ensure that
1089       <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is
1090       comprehensively written:</para>
1091
1092       <programlisting># udevadm lock --device=/dev/sda1 mkfs.ext4 /dev/sda1</programlisting>
1093     </example>
1094
1095     <example>
1096       <title>Format a RAID File System</title>
1097
1098       <para>Similar, but take locks on multiple devices at once:</para>
1099
1100       <programlisting># udevadm lock --device=/dev/sda1 --device=/dev/sdb1 mkfs.btrfs /dev/sda1 /dev/sdb1</programlisting>
1101     </example>
1102
1103     <example>
1104       <title>Copy in a File System</title>
1105
1106       <para>Take a lock on the backing block device while copying in a prepared file system image, to ensure
1107       that <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is fully
1108       written:</para>
1109
1110       <programlisting># udevadm lock -d /dev/sda1 dd if=fs.raw of=/dev/sda1</programlisting>
1111     </example>
1112   </refsect1>
1113
1114   <refsect1>
1115     <title>See Also</title>
1116     <para><simplelist type="inline">
1117       <member><citerefentry>
1118         <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
1119       </citerefentry></member>
1120       <member><citerefentry>
1121         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
1122       </citerefentry></member>
1123     </simplelist></para>
1124   </refsect1>
1125 </refentry>