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
 454             <xi:include href="version-info.xml" xpointer="v218"/>
 455           </listitem>
 456         </varlistentry>
 457         <varlistentry>
 458           <term><option>-b</option></term>
 459           <term><option>--parent-match=<replaceable>SYSPATH</replaceable></option></term>
 460           <listitem>
 461             <para>Trigger events for all children of a given device. When this option is specified more than once,
 462             then each matching result is ORed, that is, all children of each specified device are triggered.</para>
 463           </listitem>
 464         </varlistentry>
 465         <varlistentry>
 466           <term><option>--initialized-match</option></term>
 467           <term><option>--initialized-nomatch</option></term>
 468           <listitem>
 469             <para>When <option>--initialized-match</option> is specified, trigger events for devices
 470             that are already initialized by <command>systemd-udevd</command>, and skip devices that
 471             are not initialized yet.</para>
 472             <para>When <option>--initialized-nomatch</option> is specified, trigger events for devices
 473             that are not initialized by <command>systemd-udevd</command> yet, and skip devices that
 474             are already initialized.</para>
 475             <para>Typically, it is essential that applications which intend to use such a match, make
 476             sure a suitable udev rule is installed that sets at least one property on devices that
 477             shall be matched. See also Initialized Devices section below for more details.</para>
 478             <para>WARNING: <option>--initialized-nomatch</option> can potentially save a significant
 479             amount of time compared to re-triggering all devices in the system and e.g. can be used to
 480             optimize boot time. However, this is not safe to be used in a boot sequence in general.
 481             Especially, when udev rules for a device depend on its parent devices (e.g.
 482             <literal>ATTRS</literal> or <literal>IMPORT{parent}</literal> keys, see
 483             <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 484             for more details), the final state of the device becomes easily unstable with this option.
 485             </para>
 486
 487             <xi:include href="version-info.xml" xpointer="v251"/>
 488           </listitem>
 489         </varlistentry>
 490         <varlistentry>
 491           <term><option>-w</option></term>
 492           <term><option>--settle</option></term>
 493           <listitem>
 494             <para>Apart from triggering events, also waits for those events to
 495             finish. Note that this is different from calling <command>udevadm
 496             settle</command>. <command>udevadm settle</command> waits for all
 497             events to finish. This option only waits for events triggered by
 498             the same command to finish.</para>
 499
 500             <xi:include href="version-info.xml" xpointer="v238"/>
 501           </listitem>
 502         </varlistentry>
 503         <varlistentry>
 504           <term><option>--uuid</option></term>
 505           <listitem>
 506             <para>Trigger the synthetic device events, and associate a randomized UUID with each. These UUIDs
 507             are printed to standard output, one line for each event. These UUIDs are included in the uevent
 508             environment block (in the <literal>SYNTH_UUID=</literal> property) and may be used to track
 509             delivery of the generated events.</para>
 510
 511             <xi:include href="version-info.xml" xpointer="v249"/>
 512           </listitem>
 513         </varlistentry>
 514         <varlistentry>
 515           <term><option>--wait-daemon[=<replaceable>SECONDS</replaceable>]</option></term>
 516           <listitem>
 517             <para>Before triggering uevents, wait for systemd-udevd daemon to be initialized.
 518             Optionally takes timeout value. Default timeout is 5 seconds. This is equivalent to invoking
 519             <command>udevadm control --ping</command> before <command>udevadm trigger</command>.</para>
 520
 521             <xi:include href="version-info.xml" xpointer="v241"/>
 522           </listitem>
 523         </varlistentry>
 524
 525         <xi:include href="standard-options.xml" xpointer="help" />
 526       </variablelist>
 527
 528       <para>In addition, optional positional arguments can be used
 529       to specify device names or sys paths. They must start with
 530       <filename>/dev/</filename> or <filename>/sys/</filename>
 531       respectively.</para>
 532     </refsect2>
 533
 534     <refsect2><title>udevadm settle
 535       <arg choice="opt"><replaceable>options</replaceable></arg>
 536     </title>
 537       <para>Watches the udev event queue, and exits if all current events are handled.</para>
 538       <variablelist>
 539         <varlistentry>
 540           <term><option>-t</option></term>
 541           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 542           <listitem>
 543             <para>Maximum number of seconds to wait for the event
 544             queue to become empty. The default value is 120 seconds. A
 545             value of 0 will check if the queue is empty and always
 546             return immediately. A non-zero value will return an exit
 547             code of 0 if queue became empty before timeout was reached,
 548             non-zero otherwise.</para>
 549           </listitem>
 550         </varlistentry>
 551         <varlistentry>
 552           <term><option>-E</option></term>
 553           <term><option>--exit-if-exists=<replaceable>FILE</replaceable></option></term>
 554           <listitem>
 555             <para>Stop waiting if file exists.</para>
 556           </listitem>
 557         </varlistentry>
 558
 559         <xi:include href="standard-options.xml" xpointer="help" />
 560       </variablelist>
 561
 562       <para>See
 563       <citerefentry><refentrytitle>systemd-udev-settle.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 564       for more information.</para>
 565     </refsect2>
 566
 567     <refsect2><title>udevadm control <replaceable>option</replaceable></title>
 568       <para>Modify the internal state of the running udev daemon.</para>
 569       <variablelist>
 570         <varlistentry>
 571           <term><option>-e</option></term>
 572           <term><option>--exit</option></term>
 573           <listitem>
 574             <para>Signal and wait for systemd-udevd to exit. No option except for
 575             <option>--timeout</option> can be specified after this option.
 576             Note that <filename>systemd-udevd.service</filename> contains
 577             <option>Restart=always</option> and so as a result, this option restarts systemd-udevd.
 578             If you want to stop <filename>systemd-udevd.service</filename>, please use the following:
 579             <programlisting>systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd.service</programlisting>
 580             </para>
 581           </listitem>
 582         </varlistentry>
 583         <varlistentry>
 584           <term><option>-l</option></term>
 585           <term><option>--log-level=<replaceable>value</replaceable></option></term>
 586           <listitem>
 587             <para>Set the internal log level of
 588             <filename>systemd-udevd</filename>. Valid values are the
 589             numerical syslog priorities or their textual
 590             representations: <option>emerg</option>,
 591             <option>alert</option>, <option>crit</option>,
 592             <option>err</option>, <option>warning</option>,
 593             <option>notice</option>, <option>info</option>, and
 594             <option>debug</option>.</para>
 595           </listitem>
 596         </varlistentry>
 597         <varlistentry>
 598           <term><option>-s</option></term>
 599           <term><option>--stop-exec-queue</option></term>
 600           <listitem>
 601             <para>Signal systemd-udevd to stop executing new events. Incoming events
 602             will be queued.</para>
 603           </listitem>
 604         </varlistentry>
 605         <varlistentry>
 606           <term><option>-S</option></term>
 607           <term><option>--start-exec-queue</option></term>
 608           <listitem>
 609             <para>Signal systemd-udevd to enable the execution of events.</para>
 610           </listitem>
 611         </varlistentry>
 612         <varlistentry>
 613           <term><option>-R</option></term>
 614           <term><option>--reload</option></term>
 615           <listitem>
 616             <para>Signal systemd-udevd to reload the rules files and other databases like the kernel
 617             module index. Reloading rules and databases does not apply any changes to already
 618             existing devices; the new configuration will only be applied to new events.</para>
 619           </listitem>
 620         </varlistentry>
 621         <varlistentry>
 622           <term><option>-p</option></term>
 623           <term><option>--property=<replaceable>KEY</replaceable>=<replaceable>value</replaceable></option></term>
 624           <listitem>
 625             <para>Set a global property for all events.</para>
 626           </listitem>
 627         </varlistentry>
 628         <varlistentry>
 629           <term><option>-m</option></term>
 630           <term><option>--children-max=</option><replaceable>value</replaceable></term>
 631           <listitem>
 632             <para>Set the maximum number of events, systemd-udevd will handle at the same time. When 0 is
 633             specified, then the maximum is determined based on the system resources.</para>
 634           </listitem>
 635         </varlistentry>
 636         <varlistentry>
 637           <term><option>--ping</option></term>
 638           <listitem>
 639             <para>Send a ping message to systemd-udevd and wait for the reply. This may be useful to check that
 640             systemd-udevd daemon is running.</para>
 641
 642             <xi:include href="version-info.xml" xpointer="v241"/>
 643           </listitem>
 644         </varlistentry>
 645         <varlistentry>
 646           <term><option>-t</option></term>
 647           <term><option>--timeout=</option><replaceable>seconds</replaceable></term>
 648           <listitem>
 649             <para>The maximum number of seconds to wait for a reply from systemd-udevd.</para>
 650           </listitem>
 651         </varlistentry>
 652
 653         <xi:include href="standard-options.xml" xpointer="help" />
 654       </variablelist>
 655     </refsect2>
 656
 657     <refsect2><title>udevadm monitor
 658       <arg choice="opt"><replaceable>options</replaceable></arg>
 659     </title>
 660       <para>Listens to the kernel uevents and events sent out by a udev rule
 661       and prints the devpath of the event to the console. It can be used to analyze the
 662       event timing, by comparing the timestamps of the kernel uevent and the udev event.
 663       </para>
 664       <variablelist>
 665         <varlistentry>
 666           <term><option>-k</option></term>
 667           <term><option>--kernel</option></term>
 668           <listitem>
 669             <para>Print the kernel uevents.</para>
 670           </listitem>
 671         </varlistentry>
 672         <varlistentry>
 673           <term><option>-u</option></term>
 674           <term><option>--udev</option></term>
 675           <listitem>
 676             <para>Print the udev event after the rule processing.</para>
 677           </listitem>
 678         </varlistentry>
 679         <varlistentry>
 680           <term><option>-p</option></term>
 681           <term><option>--property</option></term>
 682           <listitem>
 683             <para>Also print the properties of the event.</para>
 684           </listitem>
 685         </varlistentry>
 686         <varlistentry>
 687           <term><option>-s</option></term>
 688           <term><option>--subsystem-match=<replaceable>string[/string]</replaceable></option></term>
 689           <listitem>
 690             <para>Filter kernel uevents and udev events by subsystem[/devtype]. Only events with a matching subsystem value will pass.
 691             When this option is specified more than once, then each matching result is ORed, that is, all devices in the specified
 692             subsystems are monitored.</para>
 693           </listitem>
 694         </varlistentry>
 695         <varlistentry>
 696           <term><option>-t</option></term>
 697           <term><option>--tag-match=<replaceable>string</replaceable></option></term>
 698           <listitem>
 699             <para>Filter udev events by tag. Only udev events with a given tag attached will pass.
 700             When this option is specified more than once, then each matching result is ORed, that is, devices which have one of the
 701             specified tags are monitored.</para>
 702           </listitem>
 703         </varlistentry>
 704
 705         <xi:include href="standard-options.xml" xpointer="help" />
 706       </variablelist>
 707     </refsect2>
 708
 709     <refsect2><title>udevadm test
 710       <arg choice="opt"><replaceable>options</replaceable></arg>
 711       <arg choice="opt"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
 712     </title>
 713       <para>Simulate a udev event run for the given device, and print debug output.</para>
 714       <variablelist>
 715         <varlistentry>
 716           <term><option>-a</option></term>
 717           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 718           <listitem>
 719             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 720             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 721             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 722             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 723             to list the possible actions. The default value is <literal>add</literal>.</para>
 724           </listitem>
 725         </varlistentry>
 726         <varlistentry>
 727           <term><option>-N</option></term>
 728           <term><option>--resolve-names=<constant>early</constant>|<constant>late</constant>|<constant>never</constant></option></term>
 729           <listitem>
 730             <para>Specify when udevadm should resolve names of users
 731             and groups.  When set to <constant>early</constant> (the
 732             default), names will be resolved when the rules are
 733             parsed. When set to <constant>late</constant>, names will
 734             be resolved for every event. When set to
 735             <constant>never</constant>, names will never be resolved
 736             and all devices will be owned by root.</para>
 737
 738             <xi:include href="version-info.xml" xpointer="v209"/>
 739           </listitem>
 740         </varlistentry>
 741
 742         <xi:include href="standard-options.xml" xpointer="help" />
 743       </variablelist>
 744     </refsect2>
 745
 746     <refsect2><title>udevadm test-builtin
 747       <arg choice="opt"><replaceable>options</replaceable></arg>
 748       <arg><replaceable>command</replaceable></arg>
 749       <arg choice="opt"><replaceable>devpath</replaceable>|<replaceable>file</replaceable>|<replaceable>unit</replaceable></arg>
 750     </title>
 751       <para>Run a built-in command <replaceable>COMMAND</replaceable>
 752       for device <replaceable>DEVPATH</replaceable>, and print debug
 753       output.</para>
 754       <variablelist>
 755         <varlistentry>
 756           <term><option>-a</option></term>
 757           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
 758           <listitem>
 759             <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
 760             <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
 761             <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
 762             and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
 763             to list the possible actions. The default value is <literal>add</literal>.</para>
 764
 765           <xi:include href="version-info.xml" xpointer="v250"/>
 766           </listitem>
 767         </varlistentry>
 768
 769         <xi:include href="standard-options.xml" xpointer="help" />
 770         <xi:include href="standard-options.xml" xpointer="version" />
 771       </variablelist>
 772     </refsect2>
 773
 774     <refsect2>
 775       <title>udevadm verify
 776       <arg choice="opt"><replaceable>options</replaceable></arg>
 777       <arg choice="opt" rep="repeat"><replaceable>file</replaceable></arg>
 778       …
 779       </title>
 780
 781       <para>Verify syntactic, semantic, and stylistic correctness of udev rules files.</para>
 782
 783       <para>Positional arguments could be used to specify one or more files to check.
 784       If no files are specified, the udev rules are read from the files located in
 785       the same udev/rules.d directories that are processed by the udev daemon.</para>
 786
 787       <para>The exit status is <constant>0</constant> if all specified udev
 788       rules files are syntactically, semantically, and stylistically correct,
 789       and a non-zero error code otherwise.</para>
 790
 791       <variablelist>
 792         <varlistentry>
 793           <term><option>-N</option></term>
 794           <term><option>--resolve-names=<constant>early</constant>|<constant>never</constant></option></term>
 795           <listitem>
 796             <para>Specify when udevadm should resolve names of users
 797             and groups.  When set to <constant>early</constant> (the
 798             default), names will be resolved when the rules are
 799             parsed. When set to <constant>never</constant>, names will
 800             never be resolved.</para>
 801
 802             <xi:include href="version-info.xml" xpointer="v254"/>
 803           </listitem>
 804         </varlistentry>
 805
 806         <varlistentry>
 807           <term><option>--root=<replaceable>PATH</replaceable></option></term>
 808           <listitem>
 809             <para>When looking for udev rules files located in udev/rules.d directories,
 810             operate on files underneath the specified root path <replaceable>PATH</replaceable>.</para>
 811
 812             <xi:include href="version-info.xml" xpointer="v254"/>
 813           </listitem>
 814         </varlistentry>
 815
 816         <varlistentry>
 817           <term><option>--no-summary</option></term>
 818           <listitem>
 819             <para>Do not show summary.</para>
 820
 821           <xi:include href="version-info.xml" xpointer="v254"/>
 822           </listitem>
 823         </varlistentry>
 824
 825         <varlistentry>
 826           <term><option>--no-style</option></term>
 827           <listitem>
 828             <para>Ignore style issues. When specified, even if style issues are found in udev rules files,
 829             the exit status is <constant>0</constant> if no syntactic or semantic errors are found.</para>
 830
 831             <xi:include href="version-info.xml" xpointer="v254"/>
 832           </listitem>
 833         </varlistentry>
 834
 835         <xi:include href="standard-options.xml" xpointer="help" />
 836       </variablelist>
 837     </refsect2>
 838
 839     <refsect2>
 840       <title>udevadm wait
 841       <arg choice="opt"><replaceable>options</replaceable></arg>
 842       <arg choice="opt"><replaceable>device|syspath</replaceable></arg>
 843       …
 844       </title>
 845
 846       <para>Wait for devices or device symlinks being created and initialized by
 847       <command>systemd-udevd</command>. Each device path must start with
 848       <literal>/dev/</literal> or <literal>/sys/</literal>, e.g. <literal>/dev/sda</literal>,
 849       <literal>/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1</literal>,
 850       <literal>/sys/devices/pci0000:00/0000:00:1f.6/net/eth0</literal>, or
 851       <literal>/sys/class/net/eth0</literal>. This can take multiple devices. This may be useful for
 852       waiting for devices being processed by <command>systemd-udevd</command> after e.g. partitioning
 853       or formatting the devices.</para>
 854
 855       <variablelist>
 856         <varlistentry>
 857           <term><option>-t</option></term>
 858           <term><option>--timeout=<replaceable>SECONDS</replaceable></option></term>
 859           <listitem>
 860             <para>Maximum number of seconds to wait for the specified devices or device symlinks being
 861             created, initialized, or removed. The default value is <literal>infinity</literal>.</para>
 862
 863             <xi:include href="version-info.xml" xpointer="v251"/>
 864           </listitem>
 865         </varlistentry>
 866
 867         <varlistentry>
 868           <term><option>--initialized=<replaceable>BOOL</replaceable></option></term>
 869           <listitem>
 870             <para>Check if <command>systemd-udevd</command> initialized devices. Defaults to true. When
 871             false, the command only checks if the specified devices exist. Set false to this setting if
 872             there is no udev rules for the specified devices, as the devices will never be considered
 873             as initialized in that case. See Initialized Devices section below for more details.</para>
 874
 875           <xi:include href="version-info.xml" xpointer="v251"/>
 876           </listitem>
 877         </varlistentry>
 878
 879         <varlistentry>
 880           <term><option>--removed</option></term>
 881           <listitem>
 882             <para>When specified, the command wait for devices being removed instead of created or
 883             initialized. If this is specified, <option>--initialized=</option> will be ignored.</para>
 884
 885             <xi:include href="version-info.xml" xpointer="v251"/>
 886           </listitem>
 887         </varlistentry>
 888
 889         <varlistentry>
 890           <term><option>--settle</option></term>
 891           <listitem>
 892             <para>When specified, also watches the udev event queue, and wait for all queued events
 893             being processed by <command>systemd-udevd</command>.</para>
 894
 895             <xi:include href="version-info.xml" xpointer="v251"/>
 896           </listitem>
 897         </varlistentry>
 898
 899         <xi:include href="standard-options.xml" xpointer="help" />
 900       </variablelist>
 901     </refsect2>
 902
 903     <refsect2>
 904       <title>udevadm lock
 905       <arg choice="opt"><replaceable>options</replaceable></arg>
 906       <arg choice="opt"><replaceable>command</replaceable></arg>
 907       …
 908       </title>
 909
 910       <para><command>udevadm lock</command> takes an (advisory) exclusive lock on a block device (or all
 911       specified devices), as per <ulink url="https://systemd.io/BLOCK_DEVICE_LOCKING">Locking Block Device
 912       Access</ulink> and invokes a program with the locks taken. When the invoked program exits the locks
 913       are automatically released and its return value is propagated as exit code of <command>udevadm
 914       lock</command>.</para>
 915
 916       <para>This tool is in particular useful to ensure that
 917       <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 918       does not probe a block device while changes are made to it, for example partitions created or file
 919       systems formatted. Note that many tools that interface with block devices natively support taking
 920       relevant locks, see for example
 921       <citerefentry project='man-pages'><refentrytitle>sfdisk</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
 922       <option>--lock</option> switch.</para>
 923
 924       <para>The command expects at least one block device specified via <option>--device=</option> or
 925       <option>--backing=</option>, and a command line to execute as arguments.</para>
 926
 927       <variablelist>
 928         <varlistentry>
 929           <term><option>--device=<replaceable>DEVICE</replaceable></option></term>
 930           <term><option>-d <replaceable>DEVICE</replaceable></option></term>
 931
 932           <listitem><para>Takes a path to a device node of the device to lock. This switch may be used
 933           multiple times (and in combination with <option>--backing=</option>) in order to lock multiple
 934           devices. If a partition block device node is specified the containing "whole" block device is
 935           automatically determined and used for the lock, as per the specification. If multiple devices are
 936           specified, they are deduplicated, sorted by the major/minor of their device nodes and then locked
 937           in order.</para>
 938
 939           <para>This switch must be used at least once, to specify at least one device to
 940           lock. (Alternatively, use <option>--backing=</option>, see below.)</para>
 941
 942           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 943         </varlistentry>
 944
 945         <varlistentry>
 946           <term><option>--backing=<replaceable>PATH</replaceable></option></term>
 947           <term><option>-b <replaceable>PATH</replaceable></option></term>
 948
 949           <listitem><para>If a path to a device node is specified, identical to
 950           <option>--device=</option>. However, this switch alternatively accepts a path to a regular file or
 951           directory, in which case the block device of the file system the file/directory resides on is
 952           automatically determined and used as if it was specified with
 953           <option>--device=</option>.</para>
 954
 955           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 956         </varlistentry>
 957
 958         <varlistentry>
 959           <term><option>--timeout=<replaceable>SECS</replaceable></option></term>
 960           <term><option>-t <replaceable>SECS</replaceable></option></term>
 961
 962           <listitem><para>Specifies how long to wait at most until all locks can be taken. Takes a value in
 963           seconds, or in the usual supported time units, see
 964           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>. If
 965           specified as zero the lock is attempted and if not successful the invocation will immediately
 966           fail. If passed as <literal>infinity</literal> (the default) the invocation will wait indefinitely
 967           until the lock can be acquired. If the lock cannot be taken in the specified time the specified
 968           command will not be executed and the invocation will fail.</para>
 969
 970           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 971         </varlistentry>
 972
 973         <varlistentry>
 974           <term><option>--print</option></term>
 975           <term><option>-p</option></term>
 976
 977           <listitem><para>Instead of locking the specified devices and executing a command, just print the
 978           device paths that would be locked, and execute no command. This command is useful to determine
 979           the "whole" block device in case a partition block device is specified. The devices will be sorted
 980           by their device node major number as primary ordering key and the minor number as secondary
 981           ordering key (i.e. they are shown in the order they'd be locked). Note that the number of lines
 982           printed here can be less than the number of <option>--device=</option> and
 983           <option>--backing=</option> switches specified in case these resolve to the same "whole"
 984           devices.</para>
 985
 986           <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 987         </varlistentry>
 988
 989         <xi:include href="standard-options.xml" xpointer="help" />
 990       </variablelist>
 991     </refsect2>
 992   </refsect1>
 993
 994   <refsect1>
 995     <title>Initialized Devices</title>
 996
 997     <para>Initialized devices are those for which at least one udev rule already completed execution
 998     – for any action but <literal>remove</literal> — that set a property or other device setting (and
 999     thus has an entry in the udev device database). Devices are no longer considered initialized if a
1000     <literal>remove</literal> action is seen for them (which removes their entry in the udev device
1001     database). Note that devices that have no udev rules are never considered initialized, but might
1002     still be announced via the sd-device API (or similar).</para>
1003   </refsect1>
1004
1005   <refsect1>
1006     <title>Example</title>
1007
1008     <example>
1009       <title>Format a File System</title>
1010
1011       <para>Take a lock on the backing block device while creating a file system, to ensure that
1012       <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is
1013       comprehensively written:</para>
1014
1015       <programlisting># udevadm lock --device=/dev/sda1 mkfs.ext4 /dev/sda1</programlisting>
1016     </example>
1017
1018     <example>
1019       <title>Format a RAID File System</title>
1020
1021       <para>Similar, but take locks on multiple devices at once:</para>
1022
1023       <programlisting># udevadm lock --device=/dev/sda1 --device=/dev/sdb1 mkfs.btrfs /dev/sda1 /dev/sdb1</programlisting>
1024     </example>
1025
1026     <example>
1027       <title>Copy in a File System</title>
1028
1029       <para>Take a lock on the backing block device while copying in a prepared file system image, to ensure
1030       that <command>systemd-udevd</command> doesn't probe or announce the new superblock before it is fully
1031       written:</para>
1032
1033       <programlisting># udevadm lock -d /dev/sda1 dd if=fs.raw of=/dev/sda1</programlisting>
1034     </example>
1035   </refsect1>
1036
1037   <refsect1>
1038     <title>See Also</title>
1039     <para><citerefentry>
1040         <refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum>
1041     </citerefentry>,
1042     <citerefentry>
1043         <refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum>
1044     </citerefentry></para>
1045   </refsect1>
1046 </refentry>