summaryrefslogtreecommitdiff
path: root/udev.xml
blob: 5e5388da51cd691df38e56678f90b88ac5940e8e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
<?xml version='1.0'?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<article>
  <section>
    <title>udev</title>
    <refentry>
      <refentryinfo>
        <title>udev</title>
        <date>August 2005</date>
        <productname>udev</productname>
      </refentryinfo>

      <refmeta>
        <refentrytitle>udev</refentrytitle>
        <manvolnum>7</manvolnum>
        <refmiscinfo class="version"></refmiscinfo>
      </refmeta>

      <refnamediv>
        <refname>udev</refname>
        <refpurpose>dynamic device management</refpurpose>
      </refnamediv>

      <refsect1><title>DESCRIPTION</title>
        <para>udev provides a dynamic device directory containing only the files for
        actually present devices. It creates or removes device node files in the
        <filename>/dev</filename> directory, or it renames network interfaces.</para>

        <para>Usually udev runs as <citerefentry><refentrytitle>udevd</refentrytitle>
        <manvolnum>8</manvolnum></citerefentry> and receives uevents directly from the
        kernel if a device is added or removed form the system.</para>

        <para>If udev receives a device event, it matches its configured rules
        against the available device attributes provided in sysfs to identify the device.
        Rules that match, may provide additional device information or specify a device
        node name and multiple symlink names and instruct udev to run additional programs
        as part of the device event handling.</para>
      </refsect1>

      <refsect1><title>CONFIGURATION</title>
        <para>All udev configuration files are placed in <filename>/etc/udev/*</filename>.
        Every file consists of a set of lines of text. All empty lines or lines beginning
        with '#' will be ignored.</para>

        <refsect2><title>Configuration file</title>
          <para>udev expects its main configuration file at <filename>/etc/udev/udev.conf</filename>.
          It consists of a set of variables allowing the user to override default udev values.
          The following variables can be set:</para>
          <variablelist>
            <varlistentry>
              <term><option>udev_root</option></term>
              <listitem>
                <para>Specifies where to place the device nodes in the filesystem.
                The default value is <filename>/dev</filename>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>udev_rules</option></term>
              <listitem>
                <para>The name of the udev rules file or directory to look for files
                with the suffix <filename>.rules</filename>. Multiple rule files are
                read in lexical order. The default value is
                <filename>/etc/udev/rules.d</filename>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>udev_log</option></term>
              <listitem>
                <para>The logging priority. Valid values are the numerical syslog priorities
                or their textual representations: <option>err</option>, <option>info</option>
                and <option>debug</option>.</para>
              </listitem>
            </varlistentry>
          </variablelist>
        </refsect2>

        <refsect2><title>Rules files</title>
          <para>The udev rules are read from the files located in the
          <filename>/etc/udev/rules.d</filename> directory or at the location specified
          value in the configuration file. Every line in the rules file contains at least
          one key value pair. There are two kind of keys, match and assignment keys.
          If all match keys are matching against its value, the rule gets applied and the
          assign keys get the specified value assigned. A matching rule may specify the
          name of the device node, add a symlink pointing to the node, or run a specified
          program as part of the event handling. If no matching rule is found, the default
          device node name is used.</para>

          <para>A rule may consists of a list of one or more key value pairs separated by
          a comma. Each key has a distinct operation, depending on the used operator. Valid
          operators are:</para>
          <variablelist>
            <varlistentry>
              <term><option>==</option></term>
              <listitem>
                <para>Compare for equality.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>!=</option></term>
              <listitem>
                <para>Compare for non-equality.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>=</option></term>
              <listitem>
                <para>Assign a value to a key. Keys that represent a list, are reset
                and only this single value is assigned.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>+=</option></term>
              <listitem>
                <para>Add the value to a key that holds a list of entries.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>:=</option></term>
              <listitem>
                <para>Assign  a  value  to  a key finally; disallow any later changes,
                which may be used to prevent changes by any later rules.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>The following key names can be used to match against device properties:</para>
          <variablelist>
            <varlistentry>
              <term><option>ACTION</option></term>
              <listitem>
                <para>Match the name of the event action.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>DEVPATH</option></term>
              <listitem>
                <para>Match the devpath of the event device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>KERNEL</option></term>
              <listitem>
                <para>Match the name of the event device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>SUBSYSTEM</option></term>
              <listitem>
                <para>Match the subsystem of the event device.</para>
              </listitem>
            </varlistentry>
<!--
            <varlistentry>
              <term><option>DRIVER</option></term>
              <listitem>
                <para>Match the driver name of the event device. Only set for devices created by a bus driver.</para>
              </listitem>
            </varlistentry>
-->
            <varlistentry>
              <term><option>ATTR{<replaceable>filename</replaceable>}</option></term>
              <listitem>
                <para>Match sysfs attribute values of the event device. Up to five
                <option>ATTR</option> keys can be specified per rule. Trailing
                whitespace in the attribute values is ignored, if the specified match
                value does not contain trailing whitespace itself. Depending on the type
                of operator, this key is also used to set the value of a sysfs attribute.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>KERNELS</option></term>
              <listitem>
                <para>Search the devpath upwards for a matching device name.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>SUBSYSTEMS</option></term>
              <listitem>
                <para>Search the devpath upwards for a matching device subsystem name.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>DRIVERS</option></term>
              <listitem>
                <para>Search the devpath upwards for a matching device driver name.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>ATTRS{<replaceable>filename</replaceable>}</option></term>
              <listitem>
                <para>Search the devpath upwards for a device with matching sysfs attribute values.
                Up to five <option>ATTRS</option> keys can be specified per rule. All attributes
                must match on the same device. Trailing whitespace in the attribute values is ignored,
                if the specified match value does not contain trailing whitespace itself.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>ENV{<replaceable>key</replaceable>}</option></term>
              <listitem>
                <para>Match against the value of an environment variable. Up to five <option>ENV</option>
                keys can be specified per rule. Depending on the type of operator, this key is also used
                to export a variable to the environment.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>PROGRAM</option></term>
              <listitem>
                <para>Execute external program. The key is true, if the program returns
                without exit code zero. The whole event environment is available to the
                executed program. The program's output printed to stdout is available for
                the RESULT key.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>RESULT</option></term>
              <listitem>
                <para>Match the returned string of the last PROGRAM call. This key can
                be used in the same or in any later rule after a PROGRAM call.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>Most of the fields support a shell style pattern matching. The following
          pattern characters are supported:</para>
          <variablelist>
            <varlistentry>
              <term><option>*</option></term>
              <listitem>
                <para>Matches zero, or any number of characters.</para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term><option>?</option></term>
              <listitem>
                <para>Matches any single character.</para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term><option>[]</option></term>
              <listitem>
                <para>Matches any single character specified within the brackets. For
                example, the pattern string 'tty[SR]' would match either 'ttyS' or 'ttyR'.
                Ranges are also supported within this match with the '-' character.
                For example, to match on the range of all digits, the pattern [0-9] would
                be used. If the first character following the '[' is a '!', any characters
                not enclosed are matched.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>The following keys can get values assigned:</para>
          <variablelist>
            <varlistentry>
              <term><option>NAME</option></term>
              <listitem>
                <para>The name of the node to be created, or the name the network interface
                should be renamed to. Only one rule can set the node name, all later rules with
                a NAME key will be ignored.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>SYMLINK</option></term>
              <listitem>
                <para>The name of a symlink targeting the node. Every matching rule can add
                this value to the list of symlinks to be created along with the device  node.
                Multiple symlinks may be specified by separating the names by the space
                character.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>OWNER, GROUP, MODE</option></term>
              <listitem>
                <para>The permissions for the device node. Every specified value overwrites
                the compiled-in default value.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>ATTR{<replaceable>key</replaceable>}</option></term>
              <listitem>
                <para>The value that should be written to a sysfs attribute of the
                event device. Depending on the type of operator, this key is also
                used to match against the value of a sysfs attribute.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>ENV{<replaceable>key</replaceable>}</option></term>
              <listitem>
                <para>Export a variable to the environment. Depending on the type of operator,
                this key is also to match against an environment variable.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>RUN</option></term>
              <listitem>
                <para>Add a program to the list of programs to be executed for a specific
                device. This can only be used for very short running tasks. Running an
                event process for a long period of time may block all further events for
                this or a dependent device. Long running tasks need to be immediately
                detached from the event process itself.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>LABEL</option></term>
              <listitem>
                <para>Named label where a GOTO can jump to.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>GOTO</option></term>
              <listitem>
                <para>Jumps to the next LABEL with a matching name</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>IMPORT{<replaceable>type</replaceable>}</option></term>
              <listitem>
                <para>Import a set of variables into the event environment,
                depending on <replaceable>type</replaceable>:</para>
                <variablelist>
                  <varlistentry>
                    <term><option>program</option></term>
                    <listitem>
                      <para>Execute an external program specified as the assigned value and
                      import its output, which must be in environment key format.</para>
                    </listitem>
                  </varlistentry>
                  <varlistentry>
                    <term><option>file</option></term>
                    <listitem>
                      <para>Import a text file specified as the assigned value, which must be in
                      environment key format.</para>
                    </listitem>
                  </varlistentry>
                  <varlistentry>
                    <term><option>parent</option></term>
                    <listitem>
                      <para>Import the stored keys from the parent device by reading
                      the database entry of the parent device. The value assigned to
                      <option>IMPORT{parent}</option> is used as a filter of key names
                      to import (with the same shell-style pattern matching used for
                      comparisons).</para>
                    </listitem>
                  </varlistentry>
                </variablelist>
                <para>If no option is given, udev will choose between <option>program</option>
                and <option>file</option> based on the executable bit of of the file
                permissions.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>WAIT_FOR_SYSFS</option></term>
              <listitem>
                <para>Wait for the specified sysfs file of the device to be created. Can be used
                to fight against kernel sysfs timing issues.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>OPTIONS</option></term>
              <listitem>
                <para><option>last_rule</option> stops further rules application. No later rules
                will have any effect.
                <option>ignore_device</option> will ignore this event completely.
                <option>ignore_remove</option> will ignore  any  later  remove  event  for  this
                device. This may be useful as a workaround for broken device drivers.
                <option>all_partitions</option> will create the device nodes for all available
                partitions of a block device. This may be useful for removable media devices where
                media changes are not detected.</para>
              </listitem>
            </varlistentry>
          </variablelist>

          <para>The <option>NAME</option>, <option>SYMLINK</option>, <option>PROGRAM</option>,
          <option>OWNER</option>, <option>GROUP</option>  and  <option>RUN</option>
          fields support simple printf-like string substitutions. The <option>RUN</option>
          format chars gets applied after all rules have been processed, right before the program
          is executed. It allows the use of the complete environment set by earlier matching
          rules. For all other fields, substitutions are applied while the individual rule is
          being processed. The available substitutions are:</para>
          <variablelist>
            <varlistentry>
              <term><option>$kernel</option>, <option>%k</option></term>
              <listitem>
                <para>The kernel name for this device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$number</option>, <option>%n</option></term>
              <listitem>
                <para>The kernel number for this device. For example, 'sda3' has
                kernel number of '3'</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$devpath</option>, <option>%p</option></term>
              <listitem>
                <para>The devpath of the device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$id</option>, <option>%b</option></term>
              <listitem>
                <para>The name of the device matched while searching the devpath upwards for
                  <option>SUBSYSTEMS</option>, <option>KERNELS</option>, <option>DRIVERS</option> and <option>ATTRS</option>.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$attr{<replaceable>file</replaceable>}</option>, <option>%s{<replaceable>file</replaceable>}</option></term>
              <listitem>
                <para>The value of a sysfs attribute found at the device, where
                all keys of the rule have matched. If the matching device does not have
                such an attribute, all devices along the chain of parents are searched
                for a matching attribute.
                If the attribute is a symlink, the last element of the symlink target is
                returned as the value.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$env{<replaceable>key</replaceable>}</option>, <option>%E{<replaceable>key</replaceable>}</option></term>
              <listitem>
                <para>The value of an environment variable.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$major</option>, <option>%M</option></term>
              <listitem>
                <para>The kernel major number for the device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$minor</option> <option>%m</option></term>
              <listitem>
                <para>The kernel minor number for the device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$result</option>, <option>%c</option></term>
              <listitem>
                <para>The string returned by the external program requested with PROGRAM.
                A single part of the string, separated by a space character may be selected
                by specifying the part number as an attribute: <option>%c{N}</option>.
                If the number is followed by the '+' char this part plus all remaining parts
                of the result string are substituted: <option>%c{N+}</option></para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$parent</option>, <option>%P</option></term>
              <listitem>
                <para>The node name of the parent device.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$root</option>, <option>%r</option></term>
              <listitem>
                <para>The udev_root value.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$tempnode</option>, <option>%N</option></term>
              <listitem>
                <para>The name of a created temporary device node to provide access to
                the device from a external program before the real node is created.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>%%</option></term>
              <listitem>
              <para>The '%' character itself.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><option>$$</option></term>
              <listitem>
              <para>The '$' character itself.</para>
              </listitem>
            </varlistentry>
          </variablelist>
          <para>The count of characters to be substituted may be limited by specifying
          the format length value. For example, '%3s{file}' will only
          insert the first three characters of the sysfs attribute</para>
        </refsect2>
      </refsect1>

      <refsect1><title>AUTHOR</title>
        <para>Written by Greg Kroah-Hartman <email>greg@kroah.com</email> and
        Kay Sievers <email>kay.sievers@vrfy.org</email>. With much help from
        Dan  Stekloff <email>dsteklof@us.ibm.com</email> and many others.</para>
      </refsect1>

      <refsect1>
        <title>SEE ALSO</title>
        <para><citerefentry>
            <refentrytitle>udevd</refentrytitle><manvolnum>8</manvolnum>
          </citerefentry>, 
          <citerefentry>
            <refentrytitle>udevinfo</refentrytitle><manvolnum>8</manvolnum>
          </citerefentry>, 
          <citerefentry>
            <refentrytitle>udevmonitor</refentrytitle><manvolnum>8</manvolnum>
        </citerefentry></para>
      </refsect1>
    </refentry>
  </section>
</article>