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