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