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/4.2/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 wait <optional>options</optional> <replaceable>device|syspath</replaceable></command>
  53     </cmdsynopsis>
  54     <cmdsynopsis>
  55       <command>udevadm lock <optional>options</optional> <replaceable>command</replaceable></command>
  56     </cmdsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1><title>Description</title>
  60     <para><command>udevadm</command> expects a command and command
  61     specific options.  It controls the runtime behavior of
  62     <command>systemd-udevd</command>, requests kernel events, manages
  63     the event queue, and provides simple debugging mechanisms.</para>
  64   </refsect1>
  65
  66   <refsect1><title>Options</title>
  67     <variablelist>
  68       <varlistentry>
  69         <term><option>-d</option></term>
  70         <term><option>--debug</option></term>
  71         <listitem>
  72           <para>Print debug messages to standard error. This option is implied in <command>udevadm test</command> and
  73           <command>udevadm test-builtin</command> commands.</para>
  74         </listitem>
  75       </varlistentry>
  76
  77       <xi:include href="standard-options.xml" xpointer="help" />
  78     </variablelist>
  79
  80     <refsect2><title>udevadm info
  81       <arg choice="opt"><replaceable>options</replaceable></arg>
  82       <arg choice="opt" rep="repeat"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
  83     </title>
  84
  85       <para>Query the udev database for device information.</para>
  86
  87       <para>Positional arguments should be used to specify one or more devices. Each one may be a device name
  88       (in which case it must start with <filename>/dev/</filename>), a sys path (in which case it must start
  89       with <filename>/sys/</filename>), or a systemd device unit name (in which case it must end with
  90       <literal>.device</literal>, see
  91       <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
  92       </para>
  93
  94       <variablelist>
  95         <varlistentry>
  96           <term><option>-q</option></term>
  97           <term><option>--query=<replaceable>TYPE</replaceable></option></term>
  98           <listitem>
  99             <para>Query the database for the specified type of device data.
 100             Valid <replaceable>TYPE</replaceable>s are:
 101             <constant>name</constant>, <constant>symlink</constant>,
 102             <constant>path</constant>, <constant>property</constant>,
 103             <constant>all</constant>.</para>
 104           </listitem>
 105         </varlistentry>
 106
 107         <varlistentry>
 108           <term><option>--property=<replaceable>NAME</replaceable></option></term>
 109           <listitem>
 110             <para>When showing device properties using the <option>--query=property</option>
 111             option, limit display to properties specified in the argument. The argument should
 112             be a comma-separated list of property names. If not specified, all known properties
 113             are shown.</para>
 114           </listitem>
 115         </varlistentry>
 116         <varlistentry>
 117           <term><option>--value</option></term>
 118           <listitem>
 119             <para>When showing device properties using the <option>--query=property</option>
 120             option, print only their values, and skip the property name and <literal>=</literal>.</para>
 121             <para>Cannot be used together with <option>-x/--export</option> or
 122             <option>-P/--export-prefix</option>.</para>
 123           </listitem>
 124         </varlistentry>
 125         <varlistentry>
 126           <term><option>-p</option></term>
 127           <term><option>--path=<replaceable>DEVPATH</replaceable></option></term>
 128           <listitem>
 129             <para>The <filename>/sys/</filename> path of the device to query, e.g.
 130             <filename><optional>/sys/</optional>/class/block/sda</filename>. This option is an alternative to
 131             the positional argument with a <filename>/sys/</filename> prefix. <command>udevadm info
 132             --path=/class/block/sda</command> is equivalent to <command>udevadm info
 133             /sys/class/block/sda</command>.</para>
 134           </listitem>
 135         </varlistentry>
 136         <varlistentry>
 137           <term><option>-n</option></term>
 138           <term><option>--name=<replaceable>FILE</replaceable></option></term>
 139           <listitem>
 140             <para>The name of the device node or a symlink to query,
 141             e.g. <filename><optional>/dev/</optional>/sda</filename>. This option is an alternative to the
 142             positional argument with a <filename>/dev/</filename> prefix. <command>udevadm info
 143             --name=sda</command> is equivalent to <command>udevadm info /dev/sda</command>.</para>
 144           </listitem>
 145         </varlistentry>
 146         <varlistentry>
 147           <term><option>-r</option></term>
 148           <term><option>--root</option></term>
 149           <listitem>
 150             <para>Print absolute paths in <command>name</command> or <command>symlink</command>
 151             query.</para>
 152           </listitem>
 153         </varlistentry>
 154         <varlistentry>
 155           <term><option>-a</option></term>
 156           <term><option>--attribute-walk</option></term>
 157           <listitem>
 158             <para>Print all sysfs properties of the specified device that can be used
 159             in udev rules to match the specified device. It prints all devices
 160             along the chain, up to the root of sysfs that can be used in udev rules.</para>
 161           </listitem>
 162         </varlistentry>
 163         <varlistentry>
 164           <term><option>-t</option></term>
 165           <term><option>--tree</option></term>
 166           <listitem>
 167             <para>Display a sysfs tree. This recursively iterates through the sysfs hierarchy and displays it
 168             in a tree structure. If a path is specified only the subtree below and its parent directories are
 169             shown. This will show both device and subsystem items.</para>
 170           </listitem>
 171         </varlistentry>
 172         <varlistentry>
 173           <term><option>-x</option></term>
 174           <term><option>--export</option></term>
 175           <listitem>
 176             <para>Print output as key/value pairs. Values are enclosed in single quotes.
 177             This takes effects only when <option>--query=property</option> or
 178             <option>--device-id-of-file=<replaceable>FILE</replaceable></option> is specified.</para>
 179           </listitem>
 180         </varlistentry>
 181         <varlistentry>
 182           <term><option>-P</option></term>
 183           <term><option>--export-prefix=<replaceable>NAME</replaceable></option></term>
 184           <listitem>
 185             <para>Add a prefix to the key name of exported values.
 186             This implies <option>--export</option>.</para>
 187           </listitem>
 188         </varlistentry>
 189         <varlistentry>
 190           <term><option>-d</option></term>
 191           <term><option>--device-id-of-file=<replaceable>FILE</replaceable></option></term>
 192           <listitem>
 193             <para>Print major/minor numbers of the underlying device, where the file lives on.
 194             If this is specified, all positional arguments are ignored.</para>
 195           </listitem>
 196         </varlistentry>
 197         <varlistentry>
 198           <term><option>-e</option></term>
 199           <term><option>--export-db</option></term>
 200           <listitem>
 201             <para>Export the content of the udev database.</para>
 202           </listitem>
 203         </varlistentry>
 204         <varlistentry>
 205           <term><option>-c</option></term>
 206           <term><option>--cleanup-db</option></term>
 207           <listitem>
 208             <para>Cleanup the udev database.</para>
 209           </listitem>
 210         </varlistentry>
 211         <varlistentry>
 212           <term><option>-w<optional>SECONDS</optional></option></term>
 213           <term><option>--wait-for-initialization<optional>=SECONDS</optional></option></term>
 214           <listitem>
 215             <para>Wait for device to be initialized. If argument <replaceable>SECONDS</replaceable>
 216             is not specified, the default is to wait forever.</para>
 217           </listitem>
 218         </varlistentry>
 219
 220         <xi:include href="standard-options.xml" xpointer="help" />
 221         <xi:include href="standard-options.xml" xpointer="no-pager" />
 222       </variablelist>
 223
 224       <para>The generated output shows the current device database entry in a terse format. Each line shown
 225       is prefixed with one of the following characters:</para>
 226
 227       <table>
 228         <title><command>udevadm info</command> output prefixes</title>
 229         <tgroup cols='2' align='left' colsep='1' rowsep='1'>
 230           <colspec colname="prefix" />
 231           <colspec colname="meaning" />
 232           <thead>
 233             <row>
 234               <entry>Prefix</entry>
 235               <entry>Meaning</entry>
 236             </row>
 237           </thead>
 238           <tbody>
 239             <row>
 240               <entry><literal>P:</literal></entry>
 241               <entry>Device path in <filename>/sys/</filename></entry>
 242             </row>
 243             <row>
 244               <entry><literal>M:</literal></entry>
 245               <entry>Device name in <filename>/sys/</filename> (i.e. the last component of <literal>P:</literal>)</entry>
 246             </row>
 247             <row>
 248               <entry><literal>R:</literal></entry>
 249               <entry>Device number in <filename>/sys/</filename> (i.e. the numeric suffix of the last component of <literal>P:</literal>)</entry>
 250             </row>
 251             <row>
 252               <entry><literal>U:</literal></entry>
 253               <entry>Kernel subsystem</entry>
 254             </row>
 255             <row>
 256               <entry><literal>T:</literal></entry>
 257               <entry>Kernel device type within subsystem</entry>
 258             </row>
 259             <row>
 260               <entry><literal>D:</literal></entry>
 261               <entry>Kernel device node major/minor</entry>
 262             </row>
 263             <row>
 264               <entry><literal>I:</literal></entry>
 265               <entry>Network interface index</entry>
 266             </row>
 267             <row>
 268               <entry><literal>N:</literal></entry>
 269               <entry>Kernel device node name</entry>
 270             </row>
 271             <row>
 272               <entry><literal>L:</literal></entry>
 273               <entry>Device node symlink priority</entry>
 274             </row>
 275             <row>
 276               <entry><literal>S:</literal></entry>
 277               <entry>Device node symlink</entry>
 278             </row>
 279             <row>
 280               <entry><literal>Q:</literal></entry>
 281               <entry>Block device sequence number (DISKSEQ)</entry>
 282             </row>
 283             <row>
 284               <entry><literal>V:</literal></entry>
 285               <entry>Attached driver</entry>
 286             </row>
 287             <row>
 288               <entry><literal>E:</literal></entry>
 289               <entry>Device property</entry>
 290             </row>
 291           </tbody>
 292         </tgroup>
 293       </table>
 294     </refsect2>
 295
 296     <refsect2><title>udevadm trigger
 297       <arg choice="opt"><replaceable>options</replaceable></arg>
 298       <arg choice="opt"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
 299       </title>
 300       <para>Request device events from the kernel. Primarily used to replay events at system coldplug time.</para>
 301
 302       <para>Takes device specifications as positional arguments. See the description of <command>info</command>
 303       above.</para>
 304
 305       <variablelist>
 306         <varlistentry>
 307           <term><option>-v</option></term>
 308           <term><option>--verbose</option></term>
 309           <listitem>
 310             <para>Print the list of devices which will be triggered.</para>
 311           </listitem>
 312         </varlistentry>
 313         <varlistentry>
 314           <term><option>-n</option></term>
 315           <term><option>--dry-run</option></term>
 316           <listitem>
 317             <para>Do not actually trigger the event.</para>
 318           </listitem>
 319         </varlistentry>
 320         <varlistentry>
 321           <term><option>-q</option></term>
 322           <term><option>--quiet</option></term>
 323           <listitem>
 324             <para>Suppress error logging in triggering events.</para>
 325           </listitem>
 326         </varlistentry>
 327         <varlistentry>
 328           <term><option>-t</option></term>
 329           <term><option>--type=<replaceable>TYPE</replaceable></option></term>
 330           <listitem>
 331             <para>Trigger a specific type of devices. Valid types are <literal>all</literal>,
 332             <literal>devices</literal>, and <literal>subsystems</literal>. The default value is
 333             <literal>devices</literal>.</para>
 334           </listitem>
 335         </varlistentry>
 336         <varlistentry>
 337           <term><option>-c</option></term>
 338           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 339           <listitem>
 340             <para>Type of event to be triggered. Possible actions are <literal>add</literal>,
 341             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 342             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 343             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 344             to list the possible actions. The default value is <literal>change</literal>.
 345             </para>
 346           </listitem>
 347         </varlistentry>
 348         <varlistentry>
 349           <term><option>--prioritized-subsystem=<replaceable>SUBSYSTEM<optional>,<replaceable>SUBSYSTEM</replaceable>…</optional></replaceable></option></term>
 350           <listitem>
 351             <para>Takes a comma separated list of subsystems. When triggering events for devices, the
 352             devices from the specified subsystems and their parents are triggered first. For example,
 353             if <option>--prioritized-subsystem=block,net</option>, then firstly all block devices and
 354             their parents are triggered, in the next all network devices and their parents are
 355             triggered, and lastly the other devices are triggered. This option can be specified
 356             multiple times, and in that case the lists of the subsystems will be merged. That is,
 357             <option>--prioritized-subsystem=block --prioritized-subsystem=net</option> is equivalent to
 358             <option>--prioritized-subsystem=block,net</option>.</para>
 359           </listitem>
 360         </varlistentry>
 361         <varlistentry>
 362           <term><option>-s</option></term>
 363           <term><option>--subsystem-match=<replaceable>SUBSYSTEM</replaceable></option></term>
 364           <listitem>
 365             <para>Trigger events for devices which belong to a
 366             matching subsystem. This option supports shell style pattern matching.
 367             When this option is specified more than once, then each matching result is ORed, that is,
 368             all the devices in each subsystem are triggered.</para>
 369           </listitem>
 370         </varlistentry>
 371         <varlistentry>
 372           <term><option>-S</option></term>
 373           <term><option>--subsystem-nomatch=<replaceable>SUBSYSTEM</replaceable></option></term>
 374           <listitem>
 375             <para>Do not trigger events for devices which belong to a matching subsystem. This option
 376             supports shell style pattern matching. When this option is specified more than once,
 377             then each matching result is ANDed, that is, devices which do not match all specified
 378             subsystems are triggered.</para>
 379           </listitem>
 380         </varlistentry>
 381         <varlistentry>
 382           <term><option>-a</option></term>
 383           <term><option>--attr-match=<replaceable>ATTRIBUTE</replaceable>=<replaceable>VALUE</replaceable></option></term>
 384           <listitem>
 385             <para>Trigger events for devices with a matching sysfs attribute. If a value is specified along
 386             with the attribute name, the content of the attribute is matched against the given value using
 387             shell style pattern matching. If no value is specified, the existence of the sysfs attribute is
 388             checked. When this option is specified multiple times, then each matching result is ANDed,
 389             that is, only devices which have all specified attributes are triggered.</para>
 390           </listitem>
 391         </varlistentry>
 392         <varlistentry>
 393           <term><option>-A</option></term>
 394           <term><option>--attr-nomatch=<replaceable>ATTRIBUTE</replaceable>=<replaceable>VALUE</replaceable></option></term>
 395           <listitem>
 396             <para>Do not trigger events for devices with a matching sysfs attribute. If a value is specified
 397             along with the attribute name, the content of the attribute is matched against the given value
 398             using shell style pattern matching. If no value is specified, the existence of the sysfs attribute
 399             is checked. When this option is specified multiple times, then each matching result is ANDed,
 400             that is, only devices which have none of the specified attributes are triggered.</para>
 401           </listitem>
 402         </varlistentry>
 403         <varlistentry>
 404           <term><option>-p</option></term>
 405           <term><option>--property-match=<replaceable>PROPERTY</replaceable>=<replaceable>VALUE</replaceable></option></term>
 406           <listitem>
 407             <para>Trigger events for devices with a matching property value. This option supports shell style
 408             pattern matching. When this option is specified more than once, then each matching result is ORed,
 409             that is, devices which have one of the specified properties are triggered.</para>
 410           </listitem>
 411         </varlistentry>
 412         <varlistentry>
 413           <term><option>-g</option></term>
 414           <term><option>--tag-match=<replaceable>TAG</replaceable></option></term>
 415           <listitem>
 416             <para>Trigger events for devices with a matching tag. When this option is specified multiple times,
 417             then each matching result is ANDed, that is, devices which have all specified tags are triggered.</para>
 418           </listitem>
 419         </varlistentry>
 420         <varlistentry>
 421           <term><option>-y</option></term>
 422           <term><option>--sysname-match=<replaceable>NAME</replaceable></option></term>
 423           <listitem>
 424             <para>Trigger events for devices for which the last component (i.e. the filename) of the
 425             <filename>/sys/</filename> path matches the specified <replaceable>PATH</replaceable>. This option
 426             supports shell style pattern matching. When this option is specified more than once, then each
 427             matching result is ORed, that is, all devices which have any of the specified
 428             <replaceable>NAME</replaceable> are triggered.</para>
 429           </listitem>
 430         </varlistentry>
 431         <varlistentry>
 432           <term><option>--name-match=<replaceable>NAME</replaceable></option></term>
 433           <listitem>
 434             <para>Trigger events for devices with a matching device path. When this option is specified more than once,
 435             then each matching result is ORed, that is, all specified devices are triggered.</para>
 436           </listitem>
 437         </varlistentry>
 438         <varlistentry>
 439           <term><option>-b</option></term>
 440           <term><option>--parent-match=<replaceable>SYSPATH</replaceable></option></term>
 441           <listitem>
 442             <para>Trigger events for all children of a given device. When this option is specified more than once,
 443             then each matching result is ORed, that is, all children of each specified device are triggered.</para>
 444           </listitem>
 445         </varlistentry>
 446         <varlistentry>
 447           <term><option>--initialized-match</option></term>
 448           <term><option>--initialized-nomatch</option></term>
 449           <listitem>
 450             <para>When <option>--initialized-match</option> is specified, trigger events for devices
 451             that are already initialized by <command>systemd-udevd</command>, and skip devices that
 452             are not initialized yet.</para>
 453             <para>When <option>--initialized-nomatch</option> is specified, trigger events for devices
 454             that are not initialized by <command>systemd-udevd</command> yet, and skip devices that
 455             are already initialized.</para>
 456             <para>Typically, it is essential that applications which intend to use such a match, make
 457             sure a suitable udev rule is installed that sets at least one property on devices that
 458             shall be matched. See also Initialized Devices section below for more details.</para>
 459             <para>WARNING: <option>--initialized-nomatch</option> can potentially save a significant
 460             amount of time compared to re-triggering all devices in the system and e.g. can be used to
 461             optimize boot time. However, this is not safe to be used in a boot sequence in general.
 462             Especially, when udev rules for a device depend on its parent devices (e.g.
 463             <literal>ATTRS</literal> or <literal>IMPORT{parent}</literal> keys, see
 464             <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 465             for more details), the final state of the device becomes easily unstable with this option.
 466             </para>
 467           </listitem>
 468         </varlistentry>
 469         <varlistentry>
 470           <term><option>-w</option></term>
 471           <term><option>--settle</option></term>
 472           <listitem>
 473             <para>Apart from triggering events, also waits for those events to
 474             finish. Note that this is different from calling <command>udevadm
 475             settle</command>. <command>udevadm settle</command> waits for all
 476             events to finish. This option only waits for events triggered by
 477             the same command to finish.</para>
 478           </listitem>
 479         </varlistentry>
 480         <varlistentry>
 481           <term><option>--uuid</option></term>
 482           <listitem>
 483             <para>Trigger the synthetic device events, and associate a randomized UUID with each. These UUIDs
 484             are printed to standard output, one line for each event. These UUIDs are included in the uevent
 485             environment block (in the <literal>SYNTH_UUID=</literal> property) and may be used to track
 486             delivery of the generated events.</para>
 487           </listitem>
 488         </varlistentry>
 489         <varlistentry>
 490           <term><option>--wait-daemon[=<replaceable>SECONDS</replaceable>]</option></term>
 491           <listitem>
 492             <para>Before triggering uevents, wait for systemd-udevd daemon to be initialized.
 493             Optionally takes timeout value. Default timeout is 5 seconds. This is equivalent to invoke
 494             invoking <command>udevadm control --ping</command> before <command>udevadm trigger</command>.</para>
 495           </listitem>
 496         </varlistentry>
 497
 498         <xi:include href="standard-options.xml" xpointer="help" />
 499       </variablelist>
 500
 501       <para>In addition, optional positional arguments can be used
 502       to specify device names or sys paths. They must start with
 503       <filename>/dev/</filename> or <filename>/sys/</filename>
 504       respectively.</para>
 505     </refsect2>
 506
 507     <refsect2><title>udevadm settle
 508       <arg choice="opt"><replaceable>options</replaceable></arg>
 509     </title>
 510       <para>Watches the udev event queue, and exits if all current events are handled.</para>
 511       <variablelist>
 512         <varlistentry>
 513           <term><option>-t</option></term>
 514           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 515           <listitem>
 516             <para>Maximum number of seconds to wait for the event
 517             queue to become empty. The default value is 120 seconds. A
 518             value of 0 will check if the queue is empty and always
 519             return immediately. A non-zero value will return an exit
 520             code of 0 if queue became empty before timeout was reached,
 521             non-zero otherwise.</para>
 522           </listitem>
 523         </varlistentry>
 524         <varlistentry>
 525           <term><option>-E</option></term>
 526           <term><option>--exit-if-exists=<replaceable>FILE</replaceable></option></term>
 527           <listitem>
 528             <para>Stop waiting if file exists.</para>
 529           </listitem>
 530         </varlistentry>
 531
 532         <xi:include href="standard-options.xml" xpointer="help" />
 533       </variablelist>
 534
 535       <para>See
 536       <citerefentry><refentrytitle>systemd-udev-settle.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 537       for more information.</para>
 538     </refsect2>
 539
 540     <refsect2><title>udevadm control <replaceable>option</replaceable></title>
 541       <para>Modify the internal state of the running udev daemon.</para>
 542       <variablelist>
 543         <varlistentry>
 544           <term><option>-e</option></term>
 545           <term><option>--exit</option></term>
 546           <listitem>
 547             <para>Signal and wait for systemd-udevd to exit. No option except for
 548             <option>--timeout</option> can be specified after this option.
 549             Note that <filename>systemd-udevd.service</filename> contains
 550             <option>Restart=always</option> and so as a result, this option restarts systemd-udevd.
 551             If you want to stop <filename>systemd-udevd.service</filename>, please use the following:
 552             <programlisting>systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd.service</programlisting>
 553             </para>
 554           </listitem>
 555         </varlistentry>
 556         <varlistentry>
 557           <term><option>-l</option></term>
 558           <term><option>--log-level=<replaceable>value</replaceable></option></term>
 559           <listitem>
 560             <para>Set the internal log level of
 561             <filename>systemd-udevd</filename>. Valid values are the
 562             numerical syslog priorities or their textual
 563             representations: <option>emerg</option>,
 564             <option>alert</option>, <option>crit</option>,
 565             <option>err</option>, <option>warning</option>,
 566             <option>notice</option>, <option>info</option>, and
 567             <option>debug</option>.</para>
 568           </listitem>
 569         </varlistentry>
 570         <varlistentry>
 571           <term><option>-s</option></term>
 572           <term><option>--stop-exec-queue</option></term>
 573           <listitem>
 574             <para>Signal systemd-udevd to stop executing new events. Incoming events
 575             will be queued.</para>
 576           </listitem>
 577         </varlistentry>
 578         <varlistentry>
 579           <term><option>-S</option></term>
 580           <term><option>--start-exec-queue</option></term>
 581           <listitem>
 582             <para>Signal systemd-udevd to enable the execution of events.</para>
 583           </listitem>
 584         </varlistentry>
 585         <varlistentry>
 586           <term><option>-R</option></term>
 587           <term><option>--reload</option></term>
 588           <listitem>
 589             <para>Signal systemd-udevd to reload the rules files and other databases like the kernel
 590             module index. Reloading rules and databases does not apply any changes to already
 591             existing devices; the new configuration will only be applied to new events.</para>
 592           </listitem>
 593         </varlistentry>
 594         <varlistentry>
 595           <term><option>-p</option></term>
 596           <term><option>--property=<replaceable>KEY</replaceable>=<replaceable>value</replaceable></option></term>
 597           <listitem>
 598             <para>Set a global property for all events.</para>
 599           </listitem>
 600         </varlistentry>
 601         <varlistentry>
 602           <term><option>-m</option></term>
 603           <term><option>--children-max=</option><replaceable>value</replaceable></term>
 604           <listitem>
 605             <para>Set the maximum number of events, systemd-udevd will handle at the
 606             same time.</para>
 607           </listitem>
 608         </varlistentry>
 609         <varlistentry>
 610           <term><option>--ping</option></term>
 611           <listitem>
 612             <para>Send a ping message to systemd-udevd and wait for the reply. This may be useful to check that
 613             systemd-udevd daemon is running.</para>
 614           </listitem>
 615         </varlistentry>
 616         <varlistentry>
 617           <term><option>-t</option></term>
 618           <term><option>--timeout=</option><replaceable>seconds</replaceable></term>
 619           <listitem>
 620             <para>The maximum number of seconds to wait for a reply from systemd-udevd.</para>
 621           </listitem>
 622         </varlistentry>
 623
 624         <xi:include href="standard-options.xml" xpointer="help" />
 625       </variablelist>
 626     </refsect2>
 627
 628     <refsect2><title>udevadm monitor
 629       <arg choice="opt"><replaceable>options</replaceable></arg>
 630     </title>
 631       <para>Listens to the kernel uevents and events sent out by a udev rule
 632       and prints the devpath of the event to the console. It can be used to analyze the
 633       event timing, by comparing the timestamps of the kernel uevent and the udev event.
 634       </para>
 635       <variablelist>
 636         <varlistentry>
 637           <term><option>-k</option></term>
 638           <term><option>--kernel</option></term>
 639           <listitem>
 640             <para>Print the kernel uevents.</para>
 641           </listitem>
 642         </varlistentry>
 643         <varlistentry>
 644           <term><option>-u</option></term>
 645           <term><option>--udev</option></term>
 646           <listitem>
 647             <para>Print the udev event after the rule processing.</para>
 648           </listitem>
 649         </varlistentry>
 650         <varlistentry>
 651           <term><option>-p</option></term>
 652           <term><option>--property</option></term>
 653           <listitem>
 654             <para>Also print the properties of the event.</para>
 655           </listitem>
 656         </varlistentry>
 657         <varlistentry>
 658           <term><option>-s</option></term>
 659           <term><option>--subsystem-match=<replaceable>string[/string]</replaceable></option></term>
 660           <listitem>
 661             <para>Filter kernel uevents and udev events by subsystem[/devtype]. Only events with a matching subsystem value will pass.
 662             When this option is specified more than once, then each matching result is ORed, that is, all devices in the specified
 663             subsystems are monitored.</para>
 664           </listitem>
 665         </varlistentry>
 666         <varlistentry>
 667           <term><option>-t</option></term>
 668           <term><option>--tag-match=<replaceable>string</replaceable></option></term>
 669           <listitem>
 670             <para>Filter udev events by tag. Only udev events with a given tag attached will pass.
 671             When this option is specified more than once, then each matching result is ORed, that is, devices which have one of the
 672             specified tags are monitored.</para>
 673           </listitem>
 674         </varlistentry>
 675
 676         <xi:include href="standard-options.xml" xpointer="help" />
 677       </variablelist>
 678     </refsect2>
 679
 680     <refsect2><title>udevadm test
 681       <arg choice="opt"><replaceable>options</replaceable></arg>
 682       <arg choice="opt"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
 683     </title>
 684       <para>Simulate a udev event run for the given device, and print debug output.</para>
 685       <variablelist>
 686         <varlistentry>
 687           <term><option>-a</option></term>
 688           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 689           <listitem>
 690             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 691             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 692             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 693             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 694             to list the possible actions. The default value is <literal>add</literal>.</para>
 695           </listitem>
 696         </varlistentry>
 697         <varlistentry>
 698           <term><option>-N</option></term>
 699           <term><option>--resolve-names=<constant>early</constant>|<constant>late</constant>|<constant>never</constant></option></term>
 700           <listitem>
 701             <para>Specify when udevadm should resolve names of users
 702             and groups.  When set to <constant>early</constant> (the
 703             default), names will be resolved when the rules are
 704             parsed. When set to <constant>late</constant>, names will
 705             be resolved for every event. When set to
 706             <constant>never</constant>, names will never be resolved
 707             and all devices will be owned by root.</para>
 708           </listitem>
 709         </varlistentry>
 710
 711         <xi:include href="standard-options.xml" xpointer="help" />
 712       </variablelist>
 713     </refsect2>
 714
 715     <refsect2><title>udevadm test-builtin
 716       <arg choice="opt"><replaceable>options</replaceable></arg>
 717       <arg><replaceable>command</replaceable></arg>
 718       <arg choice="opt"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
 719     </title>
 720       <para>Run a built-in command <replaceable>COMMAND</replaceable>
 721       for device <replaceable>DEVPATH</replaceable>, and print debug
 722       output.</para>
 723       <variablelist>
 724         <varlistentry>
 725           <term><option>-a</option></term>
 726           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 727           <listitem>
 728             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 729             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 730             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 731             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 732             to list the possible actions. The default value is <literal>add</literal>.</para>
 733           </listitem>
 734         </varlistentry>
 735
 736         <xi:include href="standard-options.xml" xpointer="help" />
 737       </variablelist>
 738     </refsect2>
 739
 740     <refsect2>
 741       <title>udevadm wait
 742       <arg choice="opt"><replaceable>options</replaceable></arg>
 743       <arg choice="opt"><replaceable>device|syspath</replaceable></arg>
 744       …
 745       </title>
 746
 747       <para>Wait for devices or device symlinks being created and initialized by
 748       <command>systemd-udevd</command>. Each device path must start with
 749       <literal>/dev/</literal> or <literal>/sys/</literal>, e.g. <literal>/dev/sda</literal>,
 750       <literal>/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1</literal>,
 751       <literal>/sys/devices/pci0000:00/0000:00:1f.6/net/eth0</literal>, or
 752       <literal>/sys/class/net/eth0</literal>. This can take multiple devices. This may be useful for
 753       waiting for devices being processed by <command>systemd-udevd</command> after e.g. partitioning
 754       or formatting the devices.</para>
 755
 756       <variablelist>
 757         <varlistentry>
 758           <term><option>-t</option></term>
 759           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 760           <listitem>
 761             <para>Maximum number of seconds to wait for the specified devices or device symlinks being
 762             created, initialized, or removed. The default value is <literal>infinity</literal>.</para>
 763           </listitem>
 764         </varlistentry>
 765
 766         <varlistentry>
 767           <term><option>--initialized=<replaceable>BOOL</replaceable></option></term>
 768           <listitem>
 769             <para>Check if <command>systemd-udevd</command> initialized devices. Defaults to true. When
 770             false, the command only checks if the specified devices exist. Set false to this setting if
 771             there is no udev rules for the specified devices, as the devices will never be considered
 772             as initialized in that case. See Initialized Devices section below for more details.</para>
 773           </listitem>
 774         </varlistentry>
 775
 776         <varlistentry>
 777           <term><option>--removed</option></term>
 778           <listitem>
 779             <para>When specified, the command wait for devices being removed instead of created or
 780             initialized. If this is specified, <option>--initialized=</option> will be ignored.</para>
 781           </listitem>
 782         </varlistentry>
 783
 784         <varlistentry>
 785           <term><option>--settle</option></term>
 786           <listitem>
 787             <para>When specified, also watches the udev event queue, and wait for all queued events
 788             being processed by <command>systemd-udevd</command>.</para>
 789           </listitem>
 790         </varlistentry>
 791
 792         <xi:include href="standard-options.xml" xpointer="help" />
 793       </variablelist>
 794     </refsect2>
 795
 796     <refsect2>
 797       <title>udevadm lock
 798       <arg choice="opt"><replaceable>options</replaceable></arg>
 799       <arg choice="opt"><replaceable>command</replaceable></arg>
 800       …
 801       </title>
 802
 803       <para><command>udevadm lock</command> takes an (advisory) exclusive lock on a block device (or all
 804       specified devices), as per <ulink url="https://systemd.io/BLOCK_DEVICE_LOCKING">Locking Block Device
 805       Access</ulink> and invokes a program with the locks taken. When the invoked program exits the locks
 806       are automatically released and its return value is propagated as exit code of <command>udevadm
 807       lock</command>.</para>
 808
 809       <para>This tool is in particular useful to ensure that
 810       <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 811       does not probe a block device while changes are made to it, for example partitions created or file
 812       systems formatted. Note that many tools that interface with block devices natively support taking
 813       relevant locks, see for example
 814       <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
 815       <option>--lock</option> switch.</para>
 816
 817       <para>The command expects at least one block device specified via <option>--device=</option> or
 818       <option>--backing=</option>, and a command line to execute as arguments.</para>
 819
 820       <variablelist>
 821         <varlistentry>
 822           <term><option>--device=<replaceable>DEVICE</replaceable></option></term>
 823           <term><option>-d <replaceable>DEVICE</replaceable></option></term>
 824
 825           <listitem><para>Takes a path to a device node of the device to lock. This switch may be used
 826           multiple times (and in combination with <option>--backing=</option>) in order to lock multiple
 827           devices. If a partition block device node is specified the containing "whole" block device is
 828           automatically determined and used for the lock, as per the specification. If multiple devices are
 829           specified, they are deduplicated, sorted by the major/minor of their device nodes and then locked
 830           in order.</para>
 831
 832           <para>This switch must be used at least once, to specify at least one device to
 833           lock. (Alternatively, use <option>--backing=</option>, see below.)</para></listitem>
 834         </varlistentry>
 835
 836         <varlistentry>
 837           <term><option>--backing=<replaceable>PATH</replaceable></option></term>
 838           <term><option>-b <replaceable>PATH</replaceable></option></term>
 839
 840           <listitem><para>If a path to a device node is specified, identical to
 841           <option>--device=</option>. However, this switch alternatively accepts a path to a regular file or
 842           directory, in which case the block device of the file system the file/directory resides on is
 843           automatically determined and used as if it was specified with
 844           <option>--device=</option>.</para></listitem>
 845         </varlistentry>
 846
 847         <varlistentry>
 848           <term><option>--timeout=<replaceable>SECS</replaceable></option></term>
 849           <term><option>-t <replaceable>SECS</replaceable></option></term>
 850
 851           <listitem><para>Specifies how long to wait at most until all locks can be taken. Takes a value in
 852           seconds, or in the usual supported time units, see
 853           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>. If
 854           specified as zero the lock is attempted and if not successful the invocation will immediately
 855           fail. If passed as <literal>infinity</literal> (the default) the invocation will wait indefinitely
 856           until the lock can be acquired. If the lock cannot be taken in the specified time the specified
 857           command will not be executed and the invocation will fail.</para></listitem>
 858         </varlistentry>
 859
 860         <varlistentry>
 861           <term><option>--print</option></term>
 862           <term><option>-p</option></term>
 863
 864           <listitem><para>Instead of locking the specified devices and executing a command, just print the
 865           device paths that would be locked, and execute no command. This command is useful to determine
 866           the "whole" block device in case a partition block device is specified. The devices will be sorted
 867           by their device node major number as primary ordering key and the minor number as secondary
 868           ordering key (i.e. they are shown in the order they'd be locked). Note that the number of lines
 869           printed here can be less than the number of <option>--device=</option> and
 870           <option>--backing=</option> switches specified in case these resolve to the same "whole"
 871           devices.</para></listitem>
 872         </varlistentry>
 873
 874         <xi:include href="standard-options.xml" xpointer="help" />
 875       </variablelist>
 876     </refsect2>
 877   </refsect1>
 878
 879   <refsect1>
 880     <title>Initialized Devices</title>
 881
 882     <para>Initialized devices are those for which at least one udev rule already completed execution
 883     – for any action but <literal>remove</literal> — that set a property or other device setting (and
 884     thus has an entry in the udev device database). Devices are no longer considered initialized if a
 885     <literal>remove</literal> action is seen for them (which removes their entry in the udev device
 886     database). Note that devices that have no udev rules are never considered initialized, but might
 887     still be announced via the sd-device API (or similar).</para>
 888   </refsect1>
 889
 890   <refsect1>
 891     <title>Example</title>
 892
 893     <example>
 894       <title>Format a File System</title>
 895
 896       <para>Take a lock on the backing block device while creating a file system, to ensure that
 897       <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is
 898       comprehensively written:</para>
 899
 900       <programlisting># udevadm lock --device=/dev/sda1 mkfs.ext4 /dev/sda1</programlisting>
 901     </example>
 902
 903     <example>
 904       <title>Format a RAID File System</title>
 905
 906       <para>Similar, but take locks on multiple devices at once:</para>
 907
 908       <programlisting># udevadm lock --device=/dev/sda1 --device=/dev/sdb1 mkfs.btrfs /dev/sda1 /dev/sdb1</programlisting>
 909     </example>
 910
 911     <example>
 912       <title>Copy in a File System</title>
 913
 914       <para>Take a lock on the backing block device while copying in a prepared file system image, to ensure
 915       that <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is fully
 916       written:</para>
 917
 918       <programlisting># udevadm lock -d /dev/sda1 dd if=fs.raw of=/dev/sda1</programlisting>
 919     </example>
 920   </refsect1>
 921
 922   <refsect1>
 923     <title>See Also</title>
 924     <para><citerefentry>
 925         <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
 926     </citerefentry>,
 927     <citerefentry>
 928         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
 929     </citerefentry></para>
 930   </refsect1>
 931 </refentry>