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